path: root/mm/memory.c
diff options
authorKonstantin Khlebnikov <khlebnikov@yandex-team.ru>2019-07-11 21:00:07 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2019-07-12 11:05:47 -0700
commit1e426fe28261b03f297992e89da3320b42816f4e (patch)
tree7b44fe31e28a4dc64053652cca031326935f4b92 /mm/memory.c
parentproc: use down_read_killable mmap_sem for /proc/pid/map_files (diff)
mm: use down_read_killable for locking mmap_sem in access_remote_vm
This function is used by ptrace and proc files like /proc/pid/cmdline and /proc/pid/environ. Access_remote_vm never returns error codes, all errors are ignored and only size of successfully read data is returned. So, if current task was killed we'll simply return 0 (bytes read). Mmap_sem could be locked for a long time or forever if something goes wrong. Using a killable lock permits cleanup of stuck tasks and simplifies investigation. Link: http://lkml.kernel.org/r/156007494202.3335.16782303099589302087.stgit@buzz Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru> Reviewed-by: Michal Koutný <mkoutny@suse.com> Acked-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Michal Hocko <mhocko@suse.com> Cc: Alexey Dobriyan <adobriyan@gmail.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Cyrill Gorcunov <gorcunov@gmail.com> Cc: Kirill Tkhai <ktkhai@virtuozzo.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Roman Gushchin <guro@fb.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to '')
1 files changed, 3 insertions, 1 deletions
diff --git a/mm/memory.c b/mm/memory.c
index ad4bf1a1a0ef..53bd59579861 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -4344,7 +4344,9 @@ int __access_remote_vm(struct task_struct *tsk, struct mm_struct *mm,
void *old_buf = buf;
int write = gup_flags & FOLL_WRITE;
- down_read(&mm->mmap_sem);
+ if (down_read_killable(&mm->mmap_sem))
+ return 0;
/* ignore errors, just check how much was successfully transferred */
while (len) {
int bytes, ret, offset;