This patch removes the write parameter from access_remote_vm() and replaces it with a gup_flags parameter as use of this function previously _implied_ FOLL_FORCE, whereas after this patch callers explicitly pass this flag.
We make this explicit as use of FOLL_FORCE can result in surprising behaviour (and hence bugs) within the mm subsystem.
Signed-off-by: Lorenzo Stoakes lstoakes@gmail.com --- fs/proc/base.c | 19 +++++++++++++------ include/linux/mm.h | 2 +- mm/memory.c | 11 +++-------- mm/nommu.c | 7 +++---- 4 files changed, 20 insertions(+), 19 deletions(-)
diff --git a/fs/proc/base.c b/fs/proc/base.c index c2964d8..8e65446 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -252,7 +252,7 @@ static ssize_t proc_pid_cmdline_read(struct file *file, char __user *buf, * Inherently racy -- command line shares address space * with code and data. */ - rv = access_remote_vm(mm, arg_end - 1, &c, 1, 0); + rv = access_remote_vm(mm, arg_end - 1, &c, 1, FOLL_FORCE); if (rv <= 0) goto out_free_page;
@@ -270,7 +270,8 @@ static ssize_t proc_pid_cmdline_read(struct file *file, char __user *buf, int nr_read;
_count = min3(count, len, PAGE_SIZE); - nr_read = access_remote_vm(mm, p, page, _count, 0); + nr_read = access_remote_vm(mm, p, page, _count, + FOLL_FORCE); if (nr_read < 0) rv = nr_read; if (nr_read <= 0) @@ -305,7 +306,8 @@ static ssize_t proc_pid_cmdline_read(struct file *file, char __user *buf, bool final;
_count = min3(count, len, PAGE_SIZE); - nr_read = access_remote_vm(mm, p, page, _count, 0); + nr_read = access_remote_vm(mm, p, page, _count, + FOLL_FORCE); if (nr_read < 0) rv = nr_read; if (nr_read <= 0) @@ -354,7 +356,8 @@ static ssize_t proc_pid_cmdline_read(struct file *file, char __user *buf, bool final;
_count = min3(count, len, PAGE_SIZE); - nr_read = access_remote_vm(mm, p, page, _count, 0); + nr_read = access_remote_vm(mm, p, page, _count, + FOLL_FORCE); if (nr_read < 0) rv = nr_read; if (nr_read <= 0) @@ -832,6 +835,7 @@ static ssize_t mem_rw(struct file *file, char __user *buf, unsigned long addr = *ppos; ssize_t copied; char *page; + unsigned int flags = FOLL_FORCE;
if (!mm) return 0; @@ -844,6 +848,9 @@ static ssize_t mem_rw(struct file *file, char __user *buf, if (!atomic_inc_not_zero(&mm->mm_users)) goto free;
+ if (write) + flags |= FOLL_WRITE; + while (count > 0) { int this_len = min_t(int, count, PAGE_SIZE);
@@ -852,7 +859,7 @@ static ssize_t mem_rw(struct file *file, char __user *buf, break; }
- this_len = access_remote_vm(mm, addr, page, this_len, write); + this_len = access_remote_vm(mm, addr, page, this_len, flags); if (!this_len) { if (!copied) copied = -EIO; @@ -965,7 +972,7 @@ static ssize_t environ_read(struct file *file, char __user *buf, this_len = min(max_len, this_len);
retval = access_remote_vm(mm, (env_start + src), - page, this_len, 0); + page, this_len, FOLL_FORCE);
if (retval <= 0) { ret = retval; diff --git a/include/linux/mm.h b/include/linux/mm.h index 2a481d3..3e5234e 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1268,7 +1268,7 @@ static inline int fixup_user_fault(struct task_struct *tsk,
extern int access_process_vm(struct task_struct *tsk, unsigned long addr, void *buf, int len, int write); extern int access_remote_vm(struct mm_struct *mm, unsigned long addr, - void *buf, int len, int write); + void *buf, int len, unsigned int gup_flags);
long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm, unsigned long start, unsigned long nr_pages, diff --git a/mm/memory.c b/mm/memory.c index 79ebed3..bac2d99 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -3935,19 +3935,14 @@ static int __access_remote_vm(struct task_struct *tsk, struct mm_struct *mm, * @addr: start address to access * @buf: source or destination buffer * @len: number of bytes to transfer - * @write: whether the access is a write + * @gup_flags: flags modifying lookup behaviour * * The caller must hold a reference on @mm. */ int access_remote_vm(struct mm_struct *mm, unsigned long addr, - void *buf, int len, int write) + void *buf, int len, unsigned int gup_flags) { - unsigned int flags = FOLL_FORCE; - - if (write) - flags |= FOLL_WRITE; - - return __access_remote_vm(NULL, mm, addr, buf, len, flags); + return __access_remote_vm(NULL, mm, addr, buf, len, gup_flags); }
/* diff --git a/mm/nommu.c b/mm/nommu.c index bde7df3..93d5bb5 100644 --- a/mm/nommu.c +++ b/mm/nommu.c @@ -1847,15 +1847,14 @@ static int __access_remote_vm(struct task_struct *tsk, struct mm_struct *mm, * @addr: start address to access * @buf: source or destination buffer * @len: number of bytes to transfer - * @write: whether the access is a write + * @gup_flags: flags modifying lookup behaviour * * The caller must hold a reference on @mm. */ int access_remote_vm(struct mm_struct *mm, unsigned long addr, - void *buf, int len, int write) + void *buf, int len, unsigned int gup_flags) { - return __access_remote_vm(NULL, mm, addr, buf, len, - write ? FOLL_WRITE : 0); + return __access_remote_vm(NULL, mm, addr, buf, len, gup_flags); }
/*