From: Jens Axboe axboe@kernel.dk
commit 77788775c7132a8d93c6930ab1bd84fc743c7cb7 upstream.
If we COW the identity, we assume that ->mm never changes. But this isn't true of multiple processes end up sharing the ring. Hence treat id->mm like like any other process compontent when it comes to the identity mapping. This is pretty trivial, just moving the existing grab into io_grab_identity(), and including a check for the match.
Cc: stable@vger.kernel.org # 5.10 Fixes: 1e6fa5216a0e ("io_uring: COW io_identity on mismatch") Reported-by: Christian Brauner christian.brauner@ubuntu.com: Tested-by: Christian Brauner christian.brauner@ubuntu.com: Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- fs/io_uring.c | 14 +++++++------- 1 file changed, 7 insertions(+), 7 deletions(-)
--- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -1369,6 +1369,13 @@ static bool io_grab_identity(struct io_k spin_unlock_irq(&ctx->inflight_lock); req->work.flags |= IO_WQ_WORK_FILES; } + if (!(req->work.flags & IO_WQ_WORK_MM) && + (def->work_flags & IO_WQ_WORK_MM)) { + if (id->mm != current->mm) + return false; + mmgrab(id->mm); + req->work.flags |= IO_WQ_WORK_MM; + }
return true; } @@ -1393,13 +1400,6 @@ static void io_prep_async_work(struct io req->work.flags |= IO_WQ_WORK_UNBOUND; }
- /* ->mm can never change on us */ - if (!(req->work.flags & IO_WQ_WORK_MM) && - (def->work_flags & IO_WQ_WORK_MM)) { - mmgrab(id->mm); - req->work.flags |= IO_WQ_WORK_MM; - } - /* if we fail grabbing identity, we must COW, regrab, and retry */ if (io_grab_identity(req)) return;