The udl driver crashes when fbdefio is used. The crash can be reproduced with this sequence: 1. echo 1 >/sys/module/udl/parameters/fb_defio 2. run some program that maps the framebuffer, such as 'links -g' or 'fbi' 3. allocate memory to the point where the machine starts swapping
The reason for the crash is that udl_gem_get_pages calls drm_gem_get_pages and drm_gem_get_pages allocates the pages using shmem_read_mapping_page. The shmem pages are kept on the memory management lists using the page->lru entry.
However, fbdefio reuses the page->lru entry for the list of pages that were modified, so the memory management lists are corrupted and the machine crashes when vmscan starts to scan memory.
I fixed this crash by allocating pages with "alloc_page" instead. The pages allocated with "alloc_page" have page->lru unused, and thus the system doesn't crash when fbdefio uses it.
Unable to handle kernel paging request at virtual address dead000000000200 Mem abort info: ESR = 0x96000044 Exception class = DABT (current EL), IL = 32 bits SET = 0, FnV = 0 EA = 0, S1PTW = 0 Data abort info: ISV = 0, ISS = 0x00000044 CM = 0, WnR = 1 [dead000000000200] address between user and kernel address ranges Internal error: Oops: 96000044 [#1] PREEMPT SMP Modules linked in: ip6table_filter ip6_tables iptable_filter ip_tables x_tables af_packet autofs4 udl drm_kms_helper cfbfillrect syscopyarea cfbimgblt sysfillrect sysimgblt fb_sys_fops cfbcopyarea fb font drm drm_panel_orientation_quirks mousedev hid_generic usbhid hid binfmt_misc snd_usb_audio snd_hwdep snd_usbmidi_lib snd_rawmidi snd_pcm snd_timer snd soundcore ipv6 aes_ce_blk crypto_simd cryptd aes_ce_cipher crc32_ce ghash_ce gf128mul aes_arm64 sha2_ce sha256_arm64 sha1_ce sha1_generic xhci_plat_hcd xhci_hcd sd_mod usbcore usb_common mvpp2 unix CPU: 0 PID: 39 Comm: kswapd0 Not tainted 4.16.12 #3 Hardware name: Marvell 8040 MACHIATOBin (DT) pstate: 00000085 (nzcv daIf -PAN -UAO) pc : isolate_lru_pages.isra.16+0x23c/0x2b0 lr : isolate_lru_pages.isra.16+0x104/0x2b0 sp : ffffffc13a897ac0 x29: ffffffc13a897ac0 x28: 0000000000000003 x27: 0000000000000003 x26: 0000000000000004 x25: ffffff80087e84a0 x24: ffffffc13a897b68 x23: ffffffbf04cefc60 x22: ffffffc13a897e44 x21: 0000000000000009 x20: ffffffc13a897c00 x19: ffffffc13a897b40 x18: ffffffbf04d39000 x17: 00000000fffffff8 x16: ffffffbf00000000 x15: 0000000000000006 x14: 0000000000000000 x13: 00000000000001aa x12: 400000000004001c x11: 0000000000000001 x10: 0000000000000001 x9 : 00000000000ee3ac x8 : 00000000000004a0 x7 : ffffff80087e84a0 x6 : 0000000000000000 x5 : 0000000000000000 x4 : 0000000000000002 x3 : ffffff80087e84a0 x2 : 0000000000000200 x1 : dead000000000200 x0 : 400000000004001c Process kswapd0 (pid: 39, stack limit = 0x0000000097f25571) Call trace: isolate_lru_pages.isra.16+0x23c/0x2b0 shrink_inactive_list+0xe4/0x3b0 shrink_node_memcg.constprop.19+0x374/0x630 shrink_node+0x64/0x1c8 kswapd+0x340/0x568 kthread+0x118/0x120 ret_from_fork+0x10/0x18 Code: d2804002 f85e02e0 f85e02ec f9000461 (f9000023) ---[ end trace f9f3ad3856cb2ef3 ]--- note: kswapd0[39] exited with preempt_count 1
Signed-off-by: Mikulas Patocka mpatocka@redhat.com Cc: stable@vger.kernel.org
--- drivers/gpu/drm/udl/udl_gem.c | 31 +++++++++++++++++++++++++++---- 1 file changed, 27 insertions(+), 4 deletions(-)
Index: linux-4.16.12/drivers/gpu/drm/udl/udl_gem.c =================================================================== --- linux-4.16.12.orig/drivers/gpu/drm/udl/udl_gem.c 2018-01-10 09:31:23.000000000 +0100 +++ linux-4.16.12/drivers/gpu/drm/udl/udl_gem.c 2018-05-29 17:46:10.000000000 +0200 @@ -130,28 +130,51 @@ int udl_gem_fault(struct vm_fault *vmf) int udl_gem_get_pages(struct udl_gem_object *obj) { struct page **pages; + int npages, i;
if (obj->pages) return 0;
- pages = drm_gem_get_pages(&obj->base); - if (IS_ERR(pages)) - return PTR_ERR(pages); + npages = obj->base.size >> PAGE_SHIFT; + + pages = kvmalloc_array(npages, sizeof(struct page *), GFP_KERNEL); + if (!pages) + return -ENOMEM; + + for (i = 0; i < npages; i++) { + struct page *p = alloc_page(GFP_KERNEL | __GFP_ZERO); + if (!p) + goto fail; + pages[i] = p; + }
obj->pages = pages;
return 0; + +fail: + while (i--) + put_page(pages[i]); + kvfree(pages); + return -ENOMEM; }
void udl_gem_put_pages(struct udl_gem_object *obj) { + int npages, i; + if (obj->base.import_attach) { kvfree(obj->pages); obj->pages = NULL; return; }
- drm_gem_put_pages(&obj->base, obj->pages, false, false); + npages = obj->base.size >> PAGE_SHIFT; + + for (i = 0; i < npages; i++) + put_page(obj->pages[i]); + + kvfree(obj->pages); obj->pages = NULL; }