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io_uring: don't take files/mm for a dead task 

In rare cases a task may be exiting while io_ring_exit_work() trying to
cancel/wait its requests. It's ok for __io_sq_thread_acquire_mm()
because of SQPOLL check, but is not for __io_sq_thread_acquire_files().
Play safe and fail for both of them.

Cc: stable@vger.kernel.org # 5.5+
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Pavel Begunkov 2021-01-11 04:00:31 +00:00 committed by Jens Axboe
parent d434ab6db5
commit 621fadc223
1 changed files with 5 additions and 0 deletions
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5
fs/io_uring.c
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@ -1106,6 +1106,9 @@ static void io_sq_thread_drop_mm_files(void)
static int __io_sq_thread_acquire_files(struct io_ring_ctx *ctx)
{
if (current->flags & PF_EXITING)
return -EFAULT;
if (!current->files) {
struct files_struct *files;
struct nsproxy *nsproxy;
@ -1133,6 +1136,8 @@ static int __io_sq_thread_acquire_mm(struct io_ring_ctx *ctx)
{
struct mm_struct *mm;
if (current->flags & PF_EXITING)
return -EFAULT;
if (current->mm)
return 0;