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| author | Konstantin Khlebnikov | 2019-07-12 06:00:07 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman | 2019-07-31 07:27:09 +0200 |
| commit | b07687243d4a1eac564de3fca8cb0e5b1494c024 (patch) | |
| tree | 60f7815c8c9dfe210354ecd8fc9a611df69ff7d0 /mm | |
| parent | locking/lockdep: Fix lock used or unused stats error (diff) | |
| download | kernel-qcow2-linux-b07687243d4a1eac564de3fca8cb0e5b1494c024.tar.gz kernel-qcow2-linux-b07687243d4a1eac564de3fca8cb0e5b1494c024.tar.xz kernel-qcow2-linux-b07687243d4a1eac564de3fca8cb0e5b1494c024.zip | |
mm: use down_read_killable for locking mmap_sem in access_remote_vm
[ Upstream commit 1e426fe28261b03f297992e89da3320b42816f4e ]
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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/memory.c | 4 | ||||
| -rw-r--r-- | mm/nommu.c | 3 |
2 files changed, 5 insertions, 2 deletions
diff --git a/mm/memory.c b/mm/memory.c index e0010cb870e0..fb5655b518c9 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -4491,7 +4491,9 @@ 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; diff --git a/mm/nommu.c b/mm/nommu.c index e4aac33216ae..1d63ecfc98c5 100644 --- a/mm/nommu.c +++ b/mm/nommu.c @@ -1779,7 +1779,8 @@ int __access_remote_vm(struct task_struct *tsk, struct mm_struct *mm, struct vm_area_struct *vma; int write = gup_flags & FOLL_WRITE; - down_read(&mm->mmap_sem); + if (down_read_killable(&mm->mmap_sem)) + return 0; /* the access must start within one of the target process's mappings */ vma = find_vma(mm, addr); |