This series implements mitigations for lack of DMA access control on systems without an IOMMU, which could result in the DMA accessing the system memory at unexpected times and/or unexpected addresses, possibly leading to data leakage or corruption.
For example, we plan to use the PCI-e bus for Wi-Fi and that PCI-e bus is not behind an IOMMU. As PCI-e, by design, gives the device full access to system memory, a vulnerability in the Wi-Fi firmware could easily escalate to a full system exploit (remote wifi exploits: [1a], [1b] that shows a full chain of exploits; [2], [3]).
To mitigate the security concerns, we introduce restricted DMA. Restricted DMA utilizes the existing swiotlb to bounce streaming DMA in and out of a specially allocated region and does memory allocation from the same region. The feature on its own provides a basic level of protection against the DMA overwriting buffer contents at unexpected times. However, to protect against general data leakage and system memory corruption, the system needs to provide a way to restrict the DMA to a predefined memory region (this is usually done at firmware level, e.g. MPU in ATF on some ARM platforms [4]).
[1a] https://googleprojectzero.blogspot.com/2017/04/over-air-exploiting-broadcoms... [1b] https://googleprojectzero.blogspot.com/2017/04/over-air-exploiting-broadcoms... [2] https://blade.tencent.com/en/advisories/qualpwn/ [3] https://www.bleepingcomputer.com/news/security/vulnerabilities-found-in-high... [4] https://github.com/ARM-software/arm-trusted-firmware/blob/master/plat/mediat...
v8: - Fix reserved-memory.txt and add the reg property in example. - Fix sizeof for of_property_count_elems_of_size in drivers/of/address.c#of_dma_set_restricted_buffer. - Apply Will's suggestion to try the OF node having DMA configuration in drivers/of/address.c#of_dma_set_restricted_buffer. - Fix typo in the comment of drivers/of/address.c#of_dma_set_restricted_buffer. - Add error message for PageHighMem in kernel/dma/swiotlb.c#rmem_swiotlb_device_init and move it to rmem_swiotlb_setup. - Fix the message string in rmem_swiotlb_setup.
v7: Fix debugfs, PageHighMem and comment style in rmem_swiotlb_device_init https://lore.kernel.org/patchwork/cover/1431031/
v6: Address the comments in v5 https://lore.kernel.org/patchwork/cover/1423201/
v5: Rebase on latest linux-next https://lore.kernel.org/patchwork/cover/1416899/
v4: - Fix spinlock bad magic - Use rmem->name for debugfs entry - Address the comments in v3 https://lore.kernel.org/patchwork/cover/1378113/
v3: Using only one reserved memory region for both streaming DMA and memory allocation. https://lore.kernel.org/patchwork/cover/1360992/
v2: Building on top of swiotlb. https://lore.kernel.org/patchwork/cover/1280705/
v1: Using dma_map_ops. https://lore.kernel.org/patchwork/cover/1271660/
Claire Chang (15): swiotlb: Refactor swiotlb init functions swiotlb: Refactor swiotlb_create_debugfs swiotlb: Add DMA_RESTRICTED_POOL swiotlb: Add restricted DMA pool initialization swiotlb: Add a new get_io_tlb_mem getter swiotlb: Update is_swiotlb_buffer to add a struct device argument swiotlb: Update is_swiotlb_active to add a struct device argument swiotlb: Bounce data from/to restricted DMA pool if available swiotlb: Move alloc_size to find_slots swiotlb: Refactor swiotlb_tbl_unmap_single dma-direct: Add a new wrapper __dma_direct_free_pages() swiotlb: Add restricted DMA alloc/free support. dma-direct: Allocate memory from restricted DMA pool if available dt-bindings: of: Add restricted DMA pool of: Add plumbing for restricted DMA pool
.../reserved-memory/reserved-memory.txt | 36 ++- drivers/gpu/drm/i915/gem/i915_gem_internal.c | 2 +- drivers/gpu/drm/nouveau/nouveau_ttm.c | 2 +- drivers/iommu/dma-iommu.c | 12 +- drivers/of/address.c | 25 ++ drivers/of/device.c | 3 + drivers/of/of_private.h | 5 + drivers/pci/xen-pcifront.c | 2 +- drivers/xen/swiotlb-xen.c | 2 +- include/linux/device.h | 4 + include/linux/swiotlb.h | 41 ++- kernel/dma/Kconfig | 14 + kernel/dma/direct.c | 63 +++-- kernel/dma/direct.h | 9 +- kernel/dma/swiotlb.c | 242 +++++++++++++----- 15 files changed, 362 insertions(+), 100 deletions(-)
Add a new function, swiotlb_init_io_tlb_mem, for the io_tlb_mem struct initialization to make the code reusable.
Note that we now also call set_memory_decrypted in swiotlb_init_with_tbl.
Signed-off-by: Claire Chang tientzu@chromium.org --- kernel/dma/swiotlb.c | 51 ++++++++++++++++++++++---------------------- 1 file changed, 25 insertions(+), 26 deletions(-)
diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c index 8ca7d505d61c..d3232fc19385 100644 --- a/kernel/dma/swiotlb.c +++ b/kernel/dma/swiotlb.c @@ -168,9 +168,30 @@ void __init swiotlb_update_mem_attributes(void) memset(vaddr, 0, bytes); }
-int __init swiotlb_init_with_tbl(char *tlb, unsigned long nslabs, int verbose) +static void swiotlb_init_io_tlb_mem(struct io_tlb_mem *mem, phys_addr_t start, + unsigned long nslabs, bool late_alloc) { + void *vaddr = phys_to_virt(start); unsigned long bytes = nslabs << IO_TLB_SHIFT, i; + + mem->nslabs = nslabs; + mem->start = start; + mem->end = mem->start + bytes; + mem->index = 0; + mem->late_alloc = late_alloc; + spin_lock_init(&mem->lock); + for (i = 0; i < mem->nslabs; i++) { + mem->slots[i].list = IO_TLB_SEGSIZE - io_tlb_offset(i); + mem->slots[i].orig_addr = INVALID_PHYS_ADDR; + mem->slots[i].alloc_size = 0; + } + + set_memory_decrypted((unsigned long)vaddr, bytes >> PAGE_SHIFT); + memset(vaddr, 0, bytes); +} + +int __init swiotlb_init_with_tbl(char *tlb, unsigned long nslabs, int verbose) +{ struct io_tlb_mem *mem; size_t alloc_size;
@@ -186,16 +207,8 @@ int __init swiotlb_init_with_tbl(char *tlb, unsigned long nslabs, int verbose) if (!mem) panic("%s: Failed to allocate %zu bytes align=0x%lx\n", __func__, alloc_size, PAGE_SIZE); - mem->nslabs = nslabs; - mem->start = __pa(tlb); - mem->end = mem->start + bytes; - mem->index = 0; - spin_lock_init(&mem->lock); - for (i = 0; i < mem->nslabs; i++) { - mem->slots[i].list = IO_TLB_SEGSIZE - io_tlb_offset(i); - mem->slots[i].orig_addr = INVALID_PHYS_ADDR; - mem->slots[i].alloc_size = 0; - } + + swiotlb_init_io_tlb_mem(mem, __pa(tlb), nslabs, false);
io_tlb_default_mem = mem; if (verbose) @@ -282,7 +295,6 @@ swiotlb_late_init_with_default_size(size_t default_size) int swiotlb_late_init_with_tbl(char *tlb, unsigned long nslabs) { - unsigned long bytes = nslabs << IO_TLB_SHIFT, i; struct io_tlb_mem *mem;
if (swiotlb_force == SWIOTLB_NO_FORCE) @@ -297,20 +309,7 @@ swiotlb_late_init_with_tbl(char *tlb, unsigned long nslabs) if (!mem) return -ENOMEM;
- mem->nslabs = nslabs; - mem->start = virt_to_phys(tlb); - mem->end = mem->start + bytes; - mem->index = 0; - mem->late_alloc = 1; - spin_lock_init(&mem->lock); - for (i = 0; i < mem->nslabs; i++) { - mem->slots[i].list = IO_TLB_SEGSIZE - io_tlb_offset(i); - mem->slots[i].orig_addr = INVALID_PHYS_ADDR; - mem->slots[i].alloc_size = 0; - } - - set_memory_decrypted((unsigned long)tlb, bytes >> PAGE_SHIFT); - memset(tlb, 0, bytes); + swiotlb_init_io_tlb_mem(mem, virt_to_phys(tlb), nslabs, true);
io_tlb_default_mem = mem; swiotlb_print_info();
Split the debugfs creation to make the code reusable for supporting different bounce buffer pools, e.g. restricted DMA pool.
Signed-off-by: Claire Chang tientzu@chromium.org --- kernel/dma/swiotlb.c | 25 +++++++++++++++++++------ 1 file changed, 19 insertions(+), 6 deletions(-)
diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c index d3232fc19385..b849b01a446f 100644 --- a/kernel/dma/swiotlb.c +++ b/kernel/dma/swiotlb.c @@ -64,6 +64,7 @@ enum swiotlb_force swiotlb_force;
struct io_tlb_mem *io_tlb_default_mem; +static struct dentry *debugfs_dir;
/* * Max segment that we can provide which (if pages are contingous) will @@ -662,18 +663,30 @@ EXPORT_SYMBOL_GPL(is_swiotlb_active);
#ifdef CONFIG_DEBUG_FS
-static int __init swiotlb_create_debugfs(void) +static void swiotlb_create_debugfs(struct io_tlb_mem *mem, const char *name) { - struct io_tlb_mem *mem = io_tlb_default_mem; - if (!mem) - return 0; - mem->debugfs = debugfs_create_dir("swiotlb", NULL); + return; + + mem->debugfs = debugfs_create_dir(name, debugfs_dir); debugfs_create_ulong("io_tlb_nslabs", 0400, mem->debugfs, &mem->nslabs); debugfs_create_ulong("io_tlb_used", 0400, mem->debugfs, &mem->used); +} + +static int __init swiotlb_create_default_debugfs(void) +{ + struct io_tlb_mem *mem = io_tlb_default_mem; + + if (mem) { + swiotlb_create_debugfs(mem, "swiotlb"); + debugfs_dir = mem->debugfs; + } else { + debugfs_dir = debugfs_create_dir("swiotlb", NULL); + } + return 0; }
-late_initcall(swiotlb_create_debugfs); +late_initcall(swiotlb_create_default_debugfs);
#endif
Add a new kconfig symbol, DMA_RESTRICTED_POOL, for restricted DMA pool.
Signed-off-by: Claire Chang tientzu@chromium.org --- kernel/dma/Kconfig | 14 ++++++++++++++ 1 file changed, 14 insertions(+)
diff --git a/kernel/dma/Kconfig b/kernel/dma/Kconfig index 77b405508743..3e961dc39634 100644 --- a/kernel/dma/Kconfig +++ b/kernel/dma/Kconfig @@ -80,6 +80,20 @@ config SWIOTLB bool select NEED_DMA_MAP_STATE
+config DMA_RESTRICTED_POOL + bool "DMA Restricted Pool" + depends on OF && OF_RESERVED_MEM + select SWIOTLB + help + This enables support for restricted DMA pools which provide a level of + DMA memory protection on systems with limited hardware protection + capabilities, such as those lacking an IOMMU. + + For more information see + <Documentation/devicetree/bindings/reserved-memory/reserved-memory.txt> + and <kernel/dma/swiotlb.c>. + If unsure, say "n". + # # Should be selected if we can mmap non-coherent mappings to userspace. # The only thing that is really required is a way to set an uncached bit
Add the initialization function to create restricted DMA pools from matching reserved-memory nodes.
Signed-off-by: Claire Chang tientzu@chromium.org --- include/linux/device.h | 4 +++ include/linux/swiotlb.h | 3 +- kernel/dma/swiotlb.c | 76 +++++++++++++++++++++++++++++++++++++++++ 3 files changed, 82 insertions(+), 1 deletion(-)
diff --git a/include/linux/device.h b/include/linux/device.h index 959cb9d2c9ab..e78e1ce0b1b1 100644 --- a/include/linux/device.h +++ b/include/linux/device.h @@ -416,6 +416,7 @@ struct dev_links_info { * @dma_pools: Dma pools (if dma'ble device). * @dma_mem: Internal for coherent mem override. * @cma_area: Contiguous memory area for dma allocations + * @dma_io_tlb_mem: Internal for swiotlb io_tlb_mem override. * @archdata: For arch-specific additions. * @of_node: Associated device tree node. * @fwnode: Associated device node supplied by platform firmware. @@ -521,6 +522,9 @@ struct device { #ifdef CONFIG_DMA_CMA struct cma *cma_area; /* contiguous memory area for dma allocations */ +#endif +#ifdef CONFIG_DMA_RESTRICTED_POOL + struct io_tlb_mem *dma_io_tlb_mem; #endif /* arch specific additions */ struct dev_archdata archdata; diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h index 216854a5e513..03ad6e3b4056 100644 --- a/include/linux/swiotlb.h +++ b/include/linux/swiotlb.h @@ -72,7 +72,8 @@ extern enum swiotlb_force swiotlb_force; * range check to see if the memory was in fact allocated by this * API. * @nslabs: The number of IO TLB blocks (in groups of 64) between @start and - * @end. This is command line adjustable via setup_io_tlb_npages. + * @end. For default swiotlb, this is command line adjustable via + * setup_io_tlb_npages. * @used: The number of used IO TLB block. * @list: The free list describing the number of free entries available * from each index. diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c index b849b01a446f..d99b403144a8 100644 --- a/kernel/dma/swiotlb.c +++ b/kernel/dma/swiotlb.c @@ -39,6 +39,13 @@ #ifdef CONFIG_DEBUG_FS #include <linux/debugfs.h> #endif +#ifdef CONFIG_DMA_RESTRICTED_POOL +#include <linux/io.h> +#include <linux/of.h> +#include <linux/of_fdt.h> +#include <linux/of_reserved_mem.h> +#include <linux/slab.h> +#endif
#include <asm/io.h> #include <asm/dma.h> @@ -690,3 +697,72 @@ static int __init swiotlb_create_default_debugfs(void) late_initcall(swiotlb_create_default_debugfs);
#endif + +#ifdef CONFIG_DMA_RESTRICTED_POOL +static int rmem_swiotlb_device_init(struct reserved_mem *rmem, + struct device *dev) +{ + struct io_tlb_mem *mem = rmem->priv; + unsigned long nslabs = rmem->size >> IO_TLB_SHIFT; + + if (dev->dma_io_tlb_mem) + return 0; + + /* + * Since multiple devices can share the same pool, the private data, + * io_tlb_mem struct, will be initialized by the first device attached + * to it. + */ + if (!mem) { + mem = kzalloc(struct_size(mem, slots, nslabs), GFP_KERNEL); + if (!mem) + return -ENOMEM; + + swiotlb_init_io_tlb_mem(mem, rmem->base, nslabs, false); + + rmem->priv = mem; + + if (IS_ENABLED(CONFIG_DEBUG_FS)) + swiotlb_create_debugfs(mem, rmem->name); + } + + dev->dma_io_tlb_mem = mem; + + return 0; +} + +static void rmem_swiotlb_device_release(struct reserved_mem *rmem, + struct device *dev) +{ + if (dev) + dev->dma_io_tlb_mem = NULL; +} + +static const struct reserved_mem_ops rmem_swiotlb_ops = { + .device_init = rmem_swiotlb_device_init, + .device_release = rmem_swiotlb_device_release, +}; + +static int __init rmem_swiotlb_setup(struct reserved_mem *rmem) +{ + unsigned long node = rmem->fdt_node; + + if (of_get_flat_dt_prop(node, "reusable", NULL) || + of_get_flat_dt_prop(node, "linux,cma-default", NULL) || + of_get_flat_dt_prop(node, "linux,dma-default", NULL) || + of_get_flat_dt_prop(node, "no-map", NULL)) + return -EINVAL; + + if (PageHighMem(pfn_to_page(PHYS_PFN(rmem->base)))) { + pr_err("Restricted DMA pool must be accessible within the linear mapping."); + return -EINVAL; + } + + rmem->ops = &rmem_swiotlb_ops; + pr_info("Reserved memory: created restricted DMA pool at %pa, size %ld MiB\n", + &rmem->base, (unsigned long)rmem->size / SZ_1M); + return 0; +} + +RESERVEDMEM_OF_DECLARE(dma, "restricted-dma-pool", rmem_swiotlb_setup); +#endif /* CONFIG_DMA_RESTRICTED_POOL */
Add a new getter, get_io_tlb_mem, to help select the io_tlb_mem struct. The restricted DMA pool is preferred if available.
The reason it was done this way instead of assigning the active pool to dev->dma_io_tlb_mem was because directly using dev->dma_io_tlb_mem might cause memory allocation issues for existing devices. The pool can't support atomic coherent allocation so swiotlb_alloc needs to distinguish it from the default swiotlb pool.
Signed-off-by: Claire Chang tientzu@chromium.org --- include/linux/swiotlb.h | 11 +++++++++++ 1 file changed, 11 insertions(+)
diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h index 03ad6e3b4056..b469f04cca26 100644 --- a/include/linux/swiotlb.h +++ b/include/linux/swiotlb.h @@ -2,6 +2,7 @@ #ifndef __LINUX_SWIOTLB_H #define __LINUX_SWIOTLB_H
+#include <linux/device.h> #include <linux/dma-direction.h> #include <linux/init.h> #include <linux/types.h> @@ -102,6 +103,16 @@ struct io_tlb_mem { }; extern struct io_tlb_mem *io_tlb_default_mem;
+static inline struct io_tlb_mem *get_io_tlb_mem(struct device *dev) +{ +#ifdef CONFIG_DMA_RESTRICTED_POOL + if (dev && dev->dma_io_tlb_mem) + return dev->dma_io_tlb_mem; +#endif /* CONFIG_DMA_RESTRICTED_POOL */ + + return io_tlb_default_mem; +} + static inline bool is_swiotlb_buffer(phys_addr_t paddr) { struct io_tlb_mem *mem = io_tlb_default_mem;
Update is_swiotlb_buffer to add a struct device argument. This will be useful later to allow for restricted DMA pool.
Signed-off-by: Claire Chang tientzu@chromium.org --- drivers/iommu/dma-iommu.c | 12 ++++++------ drivers/xen/swiotlb-xen.c | 2 +- include/linux/swiotlb.h | 6 +++--- kernel/dma/direct.c | 6 +++--- kernel/dma/direct.h | 6 +++--- 5 files changed, 16 insertions(+), 16 deletions(-)
diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c index 7bcdd1205535..a5df35bfd150 100644 --- a/drivers/iommu/dma-iommu.c +++ b/drivers/iommu/dma-iommu.c @@ -504,7 +504,7 @@ static void __iommu_dma_unmap_swiotlb(struct device *dev, dma_addr_t dma_addr,
__iommu_dma_unmap(dev, dma_addr, size);
- if (unlikely(is_swiotlb_buffer(phys))) + if (unlikely(is_swiotlb_buffer(dev, phys))) swiotlb_tbl_unmap_single(dev, phys, size, dir, attrs); }
@@ -575,7 +575,7 @@ static dma_addr_t __iommu_dma_map_swiotlb(struct device *dev, phys_addr_t phys, }
iova = __iommu_dma_map(dev, phys, aligned_size, prot, dma_mask); - if (iova == DMA_MAPPING_ERROR && is_swiotlb_buffer(phys)) + if (iova == DMA_MAPPING_ERROR && is_swiotlb_buffer(dev, phys)) swiotlb_tbl_unmap_single(dev, phys, org_size, dir, attrs); return iova; } @@ -781,7 +781,7 @@ static void iommu_dma_sync_single_for_cpu(struct device *dev, if (!dev_is_dma_coherent(dev)) arch_sync_dma_for_cpu(phys, size, dir);
- if (is_swiotlb_buffer(phys)) + if (is_swiotlb_buffer(dev, phys)) swiotlb_sync_single_for_cpu(dev, phys, size, dir); }
@@ -794,7 +794,7 @@ static void iommu_dma_sync_single_for_device(struct device *dev, return;
phys = iommu_iova_to_phys(iommu_get_dma_domain(dev), dma_handle); - if (is_swiotlb_buffer(phys)) + if (is_swiotlb_buffer(dev, phys)) swiotlb_sync_single_for_device(dev, phys, size, dir);
if (!dev_is_dma_coherent(dev)) @@ -815,7 +815,7 @@ static void iommu_dma_sync_sg_for_cpu(struct device *dev, if (!dev_is_dma_coherent(dev)) arch_sync_dma_for_cpu(sg_phys(sg), sg->length, dir);
- if (is_swiotlb_buffer(sg_phys(sg))) + if (is_swiotlb_buffer(dev, sg_phys(sg))) swiotlb_sync_single_for_cpu(dev, sg_phys(sg), sg->length, dir); } @@ -832,7 +832,7 @@ static void iommu_dma_sync_sg_for_device(struct device *dev, return;
for_each_sg(sgl, sg, nelems, i) { - if (is_swiotlb_buffer(sg_phys(sg))) + if (is_swiotlb_buffer(dev, sg_phys(sg))) swiotlb_sync_single_for_device(dev, sg_phys(sg), sg->length, dir);
diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c index 24d11861ac7d..0c4fb34f11ab 100644 --- a/drivers/xen/swiotlb-xen.c +++ b/drivers/xen/swiotlb-xen.c @@ -100,7 +100,7 @@ static int is_xen_swiotlb_buffer(struct device *dev, dma_addr_t dma_addr) * in our domain. Therefore _only_ check address within our domain. */ if (pfn_valid(PFN_DOWN(paddr))) - return is_swiotlb_buffer(paddr); + return is_swiotlb_buffer(dev, paddr); return 0; }
diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h index b469f04cca26..2a6cca07540b 100644 --- a/include/linux/swiotlb.h +++ b/include/linux/swiotlb.h @@ -113,9 +113,9 @@ static inline struct io_tlb_mem *get_io_tlb_mem(struct device *dev) return io_tlb_default_mem; }
-static inline bool is_swiotlb_buffer(phys_addr_t paddr) +static inline bool is_swiotlb_buffer(struct device *dev, phys_addr_t paddr) { - struct io_tlb_mem *mem = io_tlb_default_mem; + struct io_tlb_mem *mem = get_io_tlb_mem(dev);
return mem && paddr >= mem->start && paddr < mem->end; } @@ -127,7 +127,7 @@ bool is_swiotlb_active(void); void __init swiotlb_adjust_size(unsigned long size); #else #define swiotlb_force SWIOTLB_NO_FORCE -static inline bool is_swiotlb_buffer(phys_addr_t paddr) +static inline bool is_swiotlb_buffer(struct device *dev, phys_addr_t paddr) { return false; } diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c index f737e3347059..84c9feb5474a 100644 --- a/kernel/dma/direct.c +++ b/kernel/dma/direct.c @@ -343,7 +343,7 @@ void dma_direct_sync_sg_for_device(struct device *dev, for_each_sg(sgl, sg, nents, i) { phys_addr_t paddr = dma_to_phys(dev, sg_dma_address(sg));
- if (unlikely(is_swiotlb_buffer(paddr))) + if (unlikely(is_swiotlb_buffer(dev, paddr))) swiotlb_sync_single_for_device(dev, paddr, sg->length, dir);
@@ -369,7 +369,7 @@ void dma_direct_sync_sg_for_cpu(struct device *dev, if (!dev_is_dma_coherent(dev)) arch_sync_dma_for_cpu(paddr, sg->length, dir);
- if (unlikely(is_swiotlb_buffer(paddr))) + if (unlikely(is_swiotlb_buffer(dev, paddr))) swiotlb_sync_single_for_cpu(dev, paddr, sg->length, dir);
@@ -504,7 +504,7 @@ size_t dma_direct_max_mapping_size(struct device *dev) bool dma_direct_need_sync(struct device *dev, dma_addr_t dma_addr) { return !dev_is_dma_coherent(dev) || - is_swiotlb_buffer(dma_to_phys(dev, dma_addr)); + is_swiotlb_buffer(dev, dma_to_phys(dev, dma_addr)); }
/** diff --git a/kernel/dma/direct.h b/kernel/dma/direct.h index 50afc05b6f1d..13e9e7158d94 100644 --- a/kernel/dma/direct.h +++ b/kernel/dma/direct.h @@ -56,7 +56,7 @@ static inline void dma_direct_sync_single_for_device(struct device *dev, { phys_addr_t paddr = dma_to_phys(dev, addr);
- if (unlikely(is_swiotlb_buffer(paddr))) + if (unlikely(is_swiotlb_buffer(dev, paddr))) swiotlb_sync_single_for_device(dev, paddr, size, dir);
if (!dev_is_dma_coherent(dev)) @@ -73,7 +73,7 @@ static inline void dma_direct_sync_single_for_cpu(struct device *dev, arch_sync_dma_for_cpu_all(); }
- if (unlikely(is_swiotlb_buffer(paddr))) + if (unlikely(is_swiotlb_buffer(dev, paddr))) swiotlb_sync_single_for_cpu(dev, paddr, size, dir);
if (dir == DMA_FROM_DEVICE) @@ -113,7 +113,7 @@ static inline void dma_direct_unmap_page(struct device *dev, dma_addr_t addr, if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC)) dma_direct_sync_single_for_cpu(dev, addr, size, dir);
- if (unlikely(is_swiotlb_buffer(phys))) + if (unlikely(is_swiotlb_buffer(dev, phys))) swiotlb_tbl_unmap_single(dev, phys, size, dir, attrs); } #endif /* _KERNEL_DMA_DIRECT_H */
Update is_swiotlb_active to add a struct device argument. This will be useful later to allow for restricted DMA pool.
Signed-off-by: Claire Chang tientzu@chromium.org --- drivers/gpu/drm/i915/gem/i915_gem_internal.c | 2 +- drivers/gpu/drm/nouveau/nouveau_ttm.c | 2 +- drivers/pci/xen-pcifront.c | 2 +- include/linux/swiotlb.h | 4 ++-- kernel/dma/direct.c | 2 +- kernel/dma/swiotlb.c | 4 ++-- 6 files changed, 8 insertions(+), 8 deletions(-)
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_internal.c b/drivers/gpu/drm/i915/gem/i915_gem_internal.c index ce6b664b10aa..7d48c433446b 100644 --- a/drivers/gpu/drm/i915/gem/i915_gem_internal.c +++ b/drivers/gpu/drm/i915/gem/i915_gem_internal.c @@ -42,7 +42,7 @@ static int i915_gem_object_get_pages_internal(struct drm_i915_gem_object *obj)
max_order = MAX_ORDER; #ifdef CONFIG_SWIOTLB - if (is_swiotlb_active()) { + if (is_swiotlb_active(NULL)) { unsigned int max_segment;
max_segment = swiotlb_max_segment(); diff --git a/drivers/gpu/drm/nouveau/nouveau_ttm.c b/drivers/gpu/drm/nouveau/nouveau_ttm.c index 65430912ff72..d0e998b9e2e8 100644 --- a/drivers/gpu/drm/nouveau/nouveau_ttm.c +++ b/drivers/gpu/drm/nouveau/nouveau_ttm.c @@ -270,7 +270,7 @@ nouveau_ttm_init(struct nouveau_drm *drm) }
#if IS_ENABLED(CONFIG_SWIOTLB) && IS_ENABLED(CONFIG_X86) - need_swiotlb = is_swiotlb_active(); + need_swiotlb = is_swiotlb_active(NULL); #endif
ret = ttm_device_init(&drm->ttm.bdev, &nouveau_bo_driver, drm->dev->dev, diff --git a/drivers/pci/xen-pcifront.c b/drivers/pci/xen-pcifront.c index b7a8f3a1921f..6d548ce53ce7 100644 --- a/drivers/pci/xen-pcifront.c +++ b/drivers/pci/xen-pcifront.c @@ -693,7 +693,7 @@ static int pcifront_connect_and_init_dma(struct pcifront_device *pdev)
spin_unlock(&pcifront_dev_lock);
- if (!err && !is_swiotlb_active()) { + if (!err && !is_swiotlb_active(NULL)) { err = pci_xen_swiotlb_init_late(); if (err) dev_err(&pdev->xdev->dev, "Could not setup SWIOTLB!\n"); diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h index 2a6cca07540b..c530c976d18b 100644 --- a/include/linux/swiotlb.h +++ b/include/linux/swiotlb.h @@ -123,7 +123,7 @@ static inline bool is_swiotlb_buffer(struct device *dev, phys_addr_t paddr) void __init swiotlb_exit(void); unsigned int swiotlb_max_segment(void); size_t swiotlb_max_mapping_size(struct device *dev); -bool is_swiotlb_active(void); +bool is_swiotlb_active(struct device *dev); void __init swiotlb_adjust_size(unsigned long size); #else #define swiotlb_force SWIOTLB_NO_FORCE @@ -143,7 +143,7 @@ static inline size_t swiotlb_max_mapping_size(struct device *dev) return SIZE_MAX; }
-static inline bool is_swiotlb_active(void) +static inline bool is_swiotlb_active(struct device *dev) { return false; } diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c index 84c9feb5474a..7a88c34d0867 100644 --- a/kernel/dma/direct.c +++ b/kernel/dma/direct.c @@ -495,7 +495,7 @@ int dma_direct_supported(struct device *dev, u64 mask) size_t dma_direct_max_mapping_size(struct device *dev) { /* If SWIOTLB is active, use its maximum mapping size */ - if (is_swiotlb_active() && + if (is_swiotlb_active(dev) && (dma_addressing_limited(dev) || swiotlb_force == SWIOTLB_FORCE)) return swiotlb_max_mapping_size(dev); return SIZE_MAX; diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c index d99b403144a8..b2b6503ecd88 100644 --- a/kernel/dma/swiotlb.c +++ b/kernel/dma/swiotlb.c @@ -662,9 +662,9 @@ size_t swiotlb_max_mapping_size(struct device *dev) return ((size_t)IO_TLB_SIZE) * IO_TLB_SEGSIZE; }
-bool is_swiotlb_active(void) +bool is_swiotlb_active(struct device *dev) { - return io_tlb_default_mem != NULL; + return get_io_tlb_mem(dev) != NULL; } EXPORT_SYMBOL_GPL(is_swiotlb_active);
Regardless of swiotlb setting, the restricted DMA pool is preferred if available.
The restricted DMA pools provide a basic level of protection against the DMA overwriting buffer contents at unexpected times. However, to protect against general data leakage and system memory corruption, the system needs to provide a way to lock down the memory access, e.g., MPU.
Note that is_dev_swiotlb_force doesn't check if swiotlb_force == SWIOTLB_FORCE. Otherwise the memory allocation behavior with default swiotlb will be changed by the following patche ("dma-direct: Allocate memory from restricted DMA pool if available").
Signed-off-by: Claire Chang tientzu@chromium.org --- include/linux/swiotlb.h | 13 +++++++++++++ kernel/dma/direct.c | 3 ++- kernel/dma/direct.h | 3 ++- kernel/dma/swiotlb.c | 8 ++++---- 4 files changed, 21 insertions(+), 6 deletions(-)
diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h index c530c976d18b..0c5a18d9cf89 100644 --- a/include/linux/swiotlb.h +++ b/include/linux/swiotlb.h @@ -120,6 +120,15 @@ static inline bool is_swiotlb_buffer(struct device *dev, phys_addr_t paddr) return mem && paddr >= mem->start && paddr < mem->end; }
+static inline bool is_dev_swiotlb_force(struct device *dev) +{ +#ifdef CONFIG_DMA_RESTRICTED_POOL + if (dev->dma_io_tlb_mem) + return true; +#endif /* CONFIG_DMA_RESTRICTED_POOL */ + return false; +} + void __init swiotlb_exit(void); unsigned int swiotlb_max_segment(void); size_t swiotlb_max_mapping_size(struct device *dev); @@ -131,6 +140,10 @@ static inline bool is_swiotlb_buffer(struct device *dev, phys_addr_t paddr) { return false; } +static inline bool is_dev_swiotlb_force(struct device *dev) +{ + return false; +} static inline void swiotlb_exit(void) { } diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c index 7a88c34d0867..078f7087e466 100644 --- a/kernel/dma/direct.c +++ b/kernel/dma/direct.c @@ -496,7 +496,8 @@ size_t dma_direct_max_mapping_size(struct device *dev) { /* If SWIOTLB is active, use its maximum mapping size */ if (is_swiotlb_active(dev) && - (dma_addressing_limited(dev) || swiotlb_force == SWIOTLB_FORCE)) + (dma_addressing_limited(dev) || swiotlb_force == SWIOTLB_FORCE || + is_dev_swiotlb_force(dev))) return swiotlb_max_mapping_size(dev); return SIZE_MAX; } diff --git a/kernel/dma/direct.h b/kernel/dma/direct.h index 13e9e7158d94..f94813674e23 100644 --- a/kernel/dma/direct.h +++ b/kernel/dma/direct.h @@ -87,7 +87,8 @@ static inline dma_addr_t dma_direct_map_page(struct device *dev, phys_addr_t phys = page_to_phys(page) + offset; dma_addr_t dma_addr = phys_to_dma(dev, phys);
- if (unlikely(swiotlb_force == SWIOTLB_FORCE)) + if (unlikely(swiotlb_force == SWIOTLB_FORCE) || + is_dev_swiotlb_force(dev)) return swiotlb_map(dev, phys, size, dir, attrs);
if (unlikely(!dma_capable(dev, dma_addr, size, true))) { diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c index b2b6503ecd88..fa7f23fffc81 100644 --- a/kernel/dma/swiotlb.c +++ b/kernel/dma/swiotlb.c @@ -347,7 +347,7 @@ void __init swiotlb_exit(void) static void swiotlb_bounce(struct device *dev, phys_addr_t tlb_addr, size_t size, enum dma_data_direction dir) { - struct io_tlb_mem *mem = io_tlb_default_mem; + struct io_tlb_mem *mem = get_io_tlb_mem(dev); int index = (tlb_addr - mem->start) >> IO_TLB_SHIFT; phys_addr_t orig_addr = mem->slots[index].orig_addr; size_t alloc_size = mem->slots[index].alloc_size; @@ -429,7 +429,7 @@ static unsigned int wrap_index(struct io_tlb_mem *mem, unsigned int index) static int find_slots(struct device *dev, phys_addr_t orig_addr, size_t alloc_size) { - struct io_tlb_mem *mem = io_tlb_default_mem; + struct io_tlb_mem *mem = get_io_tlb_mem(dev); unsigned long boundary_mask = dma_get_seg_boundary(dev); dma_addr_t tbl_dma_addr = phys_to_dma_unencrypted(dev, mem->start) & boundary_mask; @@ -506,7 +506,7 @@ phys_addr_t swiotlb_tbl_map_single(struct device *dev, phys_addr_t orig_addr, size_t mapping_size, size_t alloc_size, enum dma_data_direction dir, unsigned long attrs) { - struct io_tlb_mem *mem = io_tlb_default_mem; + struct io_tlb_mem *mem = get_io_tlb_mem(dev); unsigned int offset = swiotlb_align_offset(dev, orig_addr); unsigned int i; int index; @@ -557,7 +557,7 @@ void swiotlb_tbl_unmap_single(struct device *hwdev, phys_addr_t tlb_addr, size_t mapping_size, enum dma_data_direction dir, unsigned long attrs) { - struct io_tlb_mem *mem = io_tlb_default_mem; + struct io_tlb_mem *mem = get_io_tlb_mem(hwdev); unsigned long flags; unsigned int offset = swiotlb_align_offset(hwdev, tlb_addr); int index = (tlb_addr - offset - mem->start) >> IO_TLB_SHIFT;
Move the maintenance of alloc_size to find_slots for better code reusability later.
Signed-off-by: Claire Chang tientzu@chromium.org --- kernel/dma/swiotlb.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-)
diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c index fa7f23fffc81..88b3471ac6a8 100644 --- a/kernel/dma/swiotlb.c +++ b/kernel/dma/swiotlb.c @@ -482,8 +482,11 @@ static int find_slots(struct device *dev, phys_addr_t orig_addr, return -1;
found: - for (i = index; i < index + nslots; i++) + for (i = index; i < index + nslots; i++) { mem->slots[i].list = 0; + mem->slots[i].alloc_size = + alloc_size - ((i - index) << IO_TLB_SHIFT); + } for (i = index - 1; io_tlb_offset(i) != IO_TLB_SEGSIZE - 1 && mem->slots[i].list; i--) @@ -538,11 +541,8 @@ phys_addr_t swiotlb_tbl_map_single(struct device *dev, phys_addr_t orig_addr, * This is needed when we sync the memory. Then we sync the buffer if * needed. */ - for (i = 0; i < nr_slots(alloc_size + offset); i++) { + for (i = 0; i < nr_slots(alloc_size + offset); i++) mem->slots[index + i].orig_addr = slot_addr(orig_addr, i); - mem->slots[index + i].alloc_size = - alloc_size - (i << IO_TLB_SHIFT); - } tlb_addr = slot_addr(mem->start, index) + offset; if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC) && (dir == DMA_TO_DEVICE || dir == DMA_BIDIRECTIONAL))
Add a new function, release_slots, to make the code reusable for supporting different bounce buffer pools, e.g. restricted DMA pool.
Signed-off-by: Claire Chang tientzu@chromium.org --- kernel/dma/swiotlb.c | 35 ++++++++++++++++++++--------------- 1 file changed, 20 insertions(+), 15 deletions(-)
diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c index 88b3471ac6a8..c4fc2e444e7a 100644 --- a/kernel/dma/swiotlb.c +++ b/kernel/dma/swiotlb.c @@ -550,27 +550,15 @@ phys_addr_t swiotlb_tbl_map_single(struct device *dev, phys_addr_t orig_addr, return tlb_addr; }
-/* - * tlb_addr is the physical address of the bounce buffer to unmap. - */ -void swiotlb_tbl_unmap_single(struct device *hwdev, phys_addr_t tlb_addr, - size_t mapping_size, enum dma_data_direction dir, - unsigned long attrs) +static void release_slots(struct device *dev, phys_addr_t tlb_addr) { - struct io_tlb_mem *mem = get_io_tlb_mem(hwdev); + struct io_tlb_mem *mem = get_io_tlb_mem(dev); unsigned long flags; - unsigned int offset = swiotlb_align_offset(hwdev, tlb_addr); + unsigned int offset = swiotlb_align_offset(dev, tlb_addr); int index = (tlb_addr - offset - mem->start) >> IO_TLB_SHIFT; int nslots = nr_slots(mem->slots[index].alloc_size + offset); int count, i;
- /* - * First, sync the memory before unmapping the entry - */ - if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC) && - (dir == DMA_FROM_DEVICE || dir == DMA_BIDIRECTIONAL)) - swiotlb_bounce(hwdev, tlb_addr, mapping_size, DMA_FROM_DEVICE); - /* * Return the buffer to the free list by setting the corresponding * entries to indicate the number of contiguous entries available. @@ -605,6 +593,23 @@ void swiotlb_tbl_unmap_single(struct device *hwdev, phys_addr_t tlb_addr, spin_unlock_irqrestore(&mem->lock, flags); }
+/* + * tlb_addr is the physical address of the bounce buffer to unmap. + */ +void swiotlb_tbl_unmap_single(struct device *dev, phys_addr_t tlb_addr, + size_t mapping_size, enum dma_data_direction dir, + unsigned long attrs) +{ + /* + * First, sync the memory before unmapping the entry + */ + if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC) && + (dir == DMA_FROM_DEVICE || dir == DMA_BIDIRECTIONAL)) + swiotlb_bounce(dev, tlb_addr, mapping_size, DMA_FROM_DEVICE); + + release_slots(dev, tlb_addr); +} + void swiotlb_sync_single_for_device(struct device *dev, phys_addr_t tlb_addr, size_t size, enum dma_data_direction dir) {
Hi Claire,
On Thu, May 27, 2021 at 08:58:30PM +0800, Claire Chang wrote:
This series implements mitigations for lack of DMA access control on systems without an IOMMU, which could result in the DMA accessing the system memory at unexpected times and/or unexpected addresses, possibly leading to data leakage or corruption.
For example, we plan to use the PCI-e bus for Wi-Fi and that PCI-e bus is not behind an IOMMU. As PCI-e, by design, gives the device full access to system memory, a vulnerability in the Wi-Fi firmware could easily escalate to a full system exploit (remote wifi exploits: [1a], [1b] that shows a full chain of exploits; [2], [3]).
To mitigate the security concerns, we introduce restricted DMA. Restricted DMA utilizes the existing swiotlb to bounce streaming DMA in and out of a specially allocated region and does memory allocation from the same region. The feature on its own provides a basic level of protection against the DMA overwriting buffer contents at unexpected times. However, to protect against general data leakage and system memory corruption, the system needs to provide a way to restrict the DMA to a predefined memory region (this is usually done at firmware level, e.g. MPU in ATF on some ARM platforms [4]).
[1a] https://googleprojectzero.blogspot.com/2017/04/over-air-exploiting-broadcoms... [1b] https://googleprojectzero.blogspot.com/2017/04/over-air-exploiting-broadcoms... [2] https://blade.tencent.com/en/advisories/qualpwn/ [3] https://www.bleepingcomputer.com/news/security/vulnerabilities-found-in-high... [4] https://github.com/ARM-software/arm-trusted-firmware/blob/master/plat/mediat...
v8:
- Fix reserved-memory.txt and add the reg property in example.
- Fix sizeof for of_property_count_elems_of_size in drivers/of/address.c#of_dma_set_restricted_buffer.
- Apply Will's suggestion to try the OF node having DMA configuration in drivers/of/address.c#of_dma_set_restricted_buffer.
- Fix typo in the comment of drivers/of/address.c#of_dma_set_restricted_buffer.
- Add error message for PageHighMem in kernel/dma/swiotlb.c#rmem_swiotlb_device_init and move it to rmem_swiotlb_setup.
- Fix the message string in rmem_swiotlb_setup.
Thanks for the v8. It works for me out of the box on arm64 under KVM, so:
Tested-by: Will Deacon will@kernel.org
Note that something seems to have gone wrong with the mail threading, so the last 5 patches ended up as a separate thread for me. Probably worth posting again with all the patches in one place, if you can.
Cheers,
Will
On Sat, Jun 5, 2021 at 1:48 AM Will Deacon will@kernel.org wrote:
Hi Claire,
On Thu, May 27, 2021 at 08:58:30PM +0800, Claire Chang wrote:
This series implements mitigations for lack of DMA access control on systems without an IOMMU, which could result in the DMA accessing the system memory at unexpected times and/or unexpected addresses, possibly leading to data leakage or corruption.
For example, we plan to use the PCI-e bus for Wi-Fi and that PCI-e bus is not behind an IOMMU. As PCI-e, by design, gives the device full access to system memory, a vulnerability in the Wi-Fi firmware could easily escalate to a full system exploit (remote wifi exploits: [1a], [1b] that shows a full chain of exploits; [2], [3]).
To mitigate the security concerns, we introduce restricted DMA. Restricted DMA utilizes the existing swiotlb to bounce streaming DMA in and out of a specially allocated region and does memory allocation from the same region. The feature on its own provides a basic level of protection against the DMA overwriting buffer contents at unexpected times. However, to protect against general data leakage and system memory corruption, the system needs to provide a way to restrict the DMA to a predefined memory region (this is usually done at firmware level, e.g. MPU in ATF on some ARM platforms [4]).
[1a] https://googleprojectzero.blogspot.com/2017/04/over-air-exploiting-broadcoms... [1b] https://googleprojectzero.blogspot.com/2017/04/over-air-exploiting-broadcoms... [2] https://blade.tencent.com/en/advisories/qualpwn/ [3] https://www.bleepingcomputer.com/news/security/vulnerabilities-found-in-high... [4] https://github.com/ARM-software/arm-trusted-firmware/blob/master/plat/mediat...
v8:
- Fix reserved-memory.txt and add the reg property in example.
- Fix sizeof for of_property_count_elems_of_size in drivers/of/address.c#of_dma_set_restricted_buffer.
- Apply Will's suggestion to try the OF node having DMA configuration in drivers/of/address.c#of_dma_set_restricted_buffer.
- Fix typo in the comment of drivers/of/address.c#of_dma_set_restricted_buffer.
- Add error message for PageHighMem in kernel/dma/swiotlb.c#rmem_swiotlb_device_init and move it to rmem_swiotlb_setup.
- Fix the message string in rmem_swiotlb_setup.
Thanks for the v8. It works for me out of the box on arm64 under KVM, so:
Tested-by: Will Deacon will@kernel.org
Note that something seems to have gone wrong with the mail threading, so the last 5 patches ended up as a separate thread for me. Probably worth posting again with all the patches in one place, if you can.
Thanks for testing.
Christoph also added some comments in v7, so I'll prepare v9.
Cheers,
Will
v9 here: https://lore.kernel.org/patchwork/cover/1445081/
On Mon, Jun 7, 2021 at 11:28 AM Claire Chang tientzu@chromium.org wrote:
On Sat, Jun 5, 2021 at 1:48 AM Will Deacon will@kernel.org wrote:
Hi Claire,
On Thu, May 27, 2021 at 08:58:30PM +0800, Claire Chang wrote:
This series implements mitigations for lack of DMA access control on systems without an IOMMU, which could result in the DMA accessing the system memory at unexpected times and/or unexpected addresses, possibly leading to data leakage or corruption.
For example, we plan to use the PCI-e bus for Wi-Fi and that PCI-e bus is not behind an IOMMU. As PCI-e, by design, gives the device full access to system memory, a vulnerability in the Wi-Fi firmware could easily escalate to a full system exploit (remote wifi exploits: [1a], [1b] that shows a full chain of exploits; [2], [3]).
To mitigate the security concerns, we introduce restricted DMA. Restricted DMA utilizes the existing swiotlb to bounce streaming DMA in and out of a specially allocated region and does memory allocation from the same region. The feature on its own provides a basic level of protection against the DMA overwriting buffer contents at unexpected times. However, to protect against general data leakage and system memory corruption, the system needs to provide a way to restrict the DMA to a predefined memory region (this is usually done at firmware level, e.g. MPU in ATF on some ARM platforms [4]).
[1a] https://googleprojectzero.blogspot.com/2017/04/over-air-exploiting-broadcoms... [1b] https://googleprojectzero.blogspot.com/2017/04/over-air-exploiting-broadcoms... [2] https://blade.tencent.com/en/advisories/qualpwn/ [3] https://www.bleepingcomputer.com/news/security/vulnerabilities-found-in-high... [4] https://github.com/ARM-software/arm-trusted-firmware/blob/master/plat/mediat...
v8:
- Fix reserved-memory.txt and add the reg property in example.
- Fix sizeof for of_property_count_elems_of_size in drivers/of/address.c#of_dma_set_restricted_buffer.
- Apply Will's suggestion to try the OF node having DMA configuration in drivers/of/address.c#of_dma_set_restricted_buffer.
- Fix typo in the comment of drivers/of/address.c#of_dma_set_restricted_buffer.
- Add error message for PageHighMem in kernel/dma/swiotlb.c#rmem_swiotlb_device_init and move it to rmem_swiotlb_setup.
- Fix the message string in rmem_swiotlb_setup.
Thanks for the v8. It works for me out of the box on arm64 under KVM, so:
Tested-by: Will Deacon will@kernel.org
Note that something seems to have gone wrong with the mail threading, so the last 5 patches ended up as a separate thread for me. Probably worth posting again with all the patches in one place, if you can.
Thanks for testing.
Christoph also added some comments in v7, so I'll prepare v9.
Cheers,
Will
dri-devel@lists.freedesktop.org
-
Claire Chang -
Will Deacon