[PATCH 5.7 039/112] io_uring: fix current->mm NULL dereference on exit

Greg Kroah-Hartman
2020-07-07T15:23:58Z

From: Pavel Begunkov <asml.silence@gmail.com>

[ Upstream commit d60b5fbc1ce8210759b568da49d149b868e7c6d3 ]

Don't reissue requests from io_iopoll_reap_events(), the task may not
have mm, which ends up with NULL. It's better to kill everything off on
exit anyway.

[ 677.734670] RIP: 0010:io_iopoll_complete+0x27e/0x630
...
[ 677.734679] Call Trace:
[ 677.734695] ? __send_signal+0x1f2/0x420
[ 677.734698] ? _raw_spin_unlock_irqrestore+0x24/0x40
[ 677.734699] ? send_signal+0xf5/0x140
[ 677.734700] io_iopoll_getevents+0x12f/0x1a0
[ 677.734702] io_iopoll_reap_events.part.0+0x5e/0xa0
[ 677.734703] io_ring_ctx_wait_and_kill+0x132/0x1c0
[ 677.734704] io_uring_release+0x20/0x30
[ 677.734706] __fput+0xcd/0x230
[ 677.734707] ____fput+0xe/0x10
[ 677.734709] task_work_run+0x67/0xa0
[ 677.734710] do_exit+0x35d/0xb70
[ 677.734712] do_group_exit+0x43/0xa0
[ 677.734713] get_signal+0x140/0x900
[ 677.734715] do_signal+0x37/0x780
[ 677.734717] ? enqueue_hrtimer+0x41/0xb0
[ 677.734718] ? recalibrate_cpu_khz+0x10/0x10
[ 677.734720] ? ktime_get+0x3e/0xa0
[ 677.734721] ? lapic_next_deadline+0x26/0x30
[ 677.734723] ? tick_program_event+0x4d/0x90
[ 677.734724] ? __hrtimer_get_next_event+0x4d/0x80
[ 677.734726] __prepare_exit_to_usermode+0x126/0x1c0
[ 677.734741] prepare_exit_to_usermode+0x9/0x40
[ 677.734742] idtentry_exit_cond_rcu+0x4c/0x60
[ 677.734743] sysvec_reschedule_ipi+0x92/0x160
[ 677.734744] ? asm_sysvec_reschedule_ipi+0xa/0x20
[ 677.734745] asm_sysvec_reschedule_ipi+0x12/0x20

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/io_uring.c | 9 +++++++++
1 file changed, 9 insertions(+)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 63a456921903e..71d281f68ed83 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -858,6 +858,7 @@ static int __io_sqe_files_update(struct io_ring_ctx *ctx,
struct io_uring_files_update *ip,
unsigned nr_args);
static int io_grab_files(struct io_kiocb *req);
+static void io_complete_rw_common(struct kiocb *kiocb, long res);
static void io_cleanup_req(struct io_kiocb *req);
static int io_file_get(struct io_submit_state *state, struct io_kiocb *req,
int fd, struct file **out_file, bool fixed);
@@ -1697,6 +1698,14 @@ static void io_iopoll_queue(struct list_head *again)
do {
req = list_first_entry(again, struct io_kiocb, list);
list_del(&req->list);
+
+ /* shouldn't happen unless io_uring is dying, cancel reqs */
+ if (unlikely(!current->mm)) {
+ io_complete_rw_common(&req->rw.kiocb, -EAGAIN);
+ io_put_req(req);
+ continue;
+ }
+
refcount_inc(&req->refs);
io_queue_async_work(req);
} while (!list_empty(again));
--
2.25.1