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| author | Jens Axboe <axboe@kernel.dk> | 2020-12-29 10:50:46 -0700 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2020-12-29 11:00:36 -0700 |
| commit | 77788775c7132a8d93c6930ab1bd84fc743c7cb7 (patch) | |
| tree | 2f5da76650d3d77b40923c6b632d23b8e15a4837 | |
| parent | 5c8fe583cce542aa0b84adc939ce85293de36e5e (diff) | |
| download | lwn-77788775c7132a8d93c6930ab1bd84fc743c7cb7.tar.gz lwn-77788775c7132a8d93c6930ab1bd84fc743c7cb7.zip | |
io_uring: don't assume mm is constant across submits
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>
| -rw-r--r-- | fs/io_uring.c | 14 |
1 files changed, 7 insertions, 7 deletions
diff --git a/fs/io_uring.c b/fs/io_uring.c index 7e35283fc0b1..eb4620ff638e 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -1501,6 +1501,13 @@ static bool io_grab_identity(struct io_kiocb *req) 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; } @@ -1525,13 +1532,6 @@ static void io_prep_async_work(struct io_kiocb *req) 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; |