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io_uring: only allow submit from owning task 

If the credentials or the mm doesn't match, don't allow the task to
submit anything on behalf of this ring. The task that owns the ring can
pass the file descriptor to another task, but we don't want to allow
that task to submit an SQE that then assumes the ring mm and creds if
it needs to go async.

Cc: stable@vger.kernel.org
Suggested-by: Stefan Metzmacher <metze@samba.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
alistair/sunxi64-5.5-dsi
Jens Axboe 2020-01-16 19:00:24 -07:00
parent 11ba820bf1
commit 44d282796f
1 changed files with 6 additions and 0 deletions
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6
fs/io_uring.c
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@ -5159,6 +5159,12 @@ SYSCALL_DEFINE6(io_uring_enter, unsigned int, fd, u32, to_submit,
} else if (to_submit) {
struct mm_struct *cur_mm;
if (current->mm != ctx->sqo_mm ||
current_cred() != ctx->creds) {
ret = -EPERM;
goto out;
}
to_submit = min(to_submit, ctx->sq_entries);
mutex_lock(&ctx->uring_lock);
/* already have mm, so io_submit_sqes() won't try to grab it */