proc: make sure mem_open() doesn't pin the target's memory
Once /proc/pid/mem is opened, the memory can't be released until mem_release() even if its owner exits. Change mem_open() to do atomic_inc(mm_count) + mmput(), this only pins mm_struct. Change mem_rw() to do atomic_inc_not_zero(mm_count) before access_remote_vm(), this verifies that this mm is still alive. I am not sure what should mem_rw() return if atomic_inc_not_zero() fails. With this patch it returns zero to match the "mm == NULL" case, may be it should return -EINVAL like it did before e268337d . Perhaps it makes sense to add the additional fatal_signal_pending() check into the main loop, to ensure we do not hold this memory if the target task was oom-killed. Cc: stable@kernel.org Signed-off-by:Oleg Nesterov <oleg@redhat.com> Signed-off-by:
Linus Torvalds <torvalds@linux-foundation.org>
parent
572d34b9
Please register or sign in to comment