[PATCH v2 0/2] fix failing request submission

[PATCH v2 0/2] fix failing request submission

[Pavel Begunkov]

Fix small problems with new link fail logic

v2: set REQ_F_LINK after clearing HARDLINK, leaking reqs otherwise (Hao)

Pavel Begunkov (2):
  io_uring: fix queueing half-created requests
  io_uring: don't submit half-prepared drain request

 fs/io_uring.c | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

-- 
2.33.0

[PATCH v2 1/2] io_uring: fix queueing half-created requests

[Pavel Begunkov]

[   27.259845] general protection fault, probably for non-canonical address 0xdffffc0000000005: 0000 [#1] SMP KASAN PTI
[   27.261043] KASAN: null-ptr-deref in range [0x0000000000000028-0x000000000000002f]
[   27.263730] RIP: 0010:sock_from_file+0x20/0x90
[   27.272444] Call Trace:
[   27.272736]  io_sendmsg+0x98/0x600
[   27.279216]  io_issue_sqe+0x498/0x68d0
[   27.281142]  __io_queue_sqe+0xab/0xb50
[   27.285830]  io_req_task_submit+0xbf/0x1b0
[   27.286306]  tctx_task_work+0x178/0xad0
[   27.288211]  task_work_run+0xe2/0x190
[   27.288571]  exit_to_user_mode_prepare+0x1a1/0x1b0
[   27.289041]  syscall_exit_to_user_mode+0x19/0x50
[   27.289521]  do_syscall_64+0x48/0x90
[   27.289871]  entry_SYSCALL_64_after_hwframe+0x44/0xae

io_req_complete_failed() -> io_req_complete_post() ->
io_req_task_queue() still would try to enqueue hard linked request,
which can be half prepared (e.g. failed init), so we can't allow
that to happen.

Fixes: a8295b982c46d ("io_uring: fix failed linkchain code logic")
Reported-by: syzbot+f9704d1878e290eddf73@syzkaller.appspotmail.com
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 fs/io_uring.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 473a977c7979..6e07456d9842 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -1823,6 +1823,17 @@ static void io_req_complete_failed(struct io_kiocb *req, long res)
 	io_req_complete_post(req, res, 0);
 }
 
+static void io_req_complete_fail_submit(struct io_kiocb *req)
+{
+	/*
+	 * We don't submit, fail them all, for that replace hardlinks with
+	 * normal links. Extra REQ_F_LINK is tolerated.
+	 */
+	req->flags &= ~REQ_F_HARDLINK;
+	req->flags |= REQ_F_LINK;
+	io_req_complete_failed(req, req->result);
+}
+
 /*
  * Don't initialise the fields below on every allocation, but do that in
  * advance and keep them valid across allocations.
@@ -6717,7 +6728,7 @@ static inline void io_queue_sqe(struct io_kiocb *req)
 	if (likely(!(req->flags & (REQ_F_FORCE_ASYNC | REQ_F_FAIL)))) {
 		__io_queue_sqe(req);
 	} else if (req->flags & REQ_F_FAIL) {
-		io_req_complete_failed(req, req->result);
+		io_req_complete_fail_submit(req);
 	} else {
 		int ret = io_req_prep_async(req);
 
-- 
2.33.0

[PATCH v2 2/2] io_uring: don't submit half-prepared drain request

[Pavel Begunkov]

[ 3784.910888] BUG: kernel NULL pointer dereference, address: 0000000000000020
[ 3784.910904] RIP: 0010:__io_file_supports_nowait+0x5/0xc0
[ 3784.910926] Call Trace:
[ 3784.910928]  ? io_read+0x17c/0x480
[ 3784.910945]  io_issue_sqe+0xcb/0x1840
[ 3784.910953]  __io_queue_sqe+0x44/0x300
[ 3784.910959]  io_req_task_submit+0x27/0x70
[ 3784.910962]  tctx_task_work+0xeb/0x1d0
[ 3784.910966]  task_work_run+0x61/0xa0
[ 3784.910968]  io_run_task_work_sig+0x53/0xa0
[ 3784.910975]  __x64_sys_io_uring_enter+0x22/0x30
[ 3784.910977]  do_syscall_64+0x3d/0x90
[ 3784.910981]  entry_SYSCALL_64_after_hwframe+0x44/0xae

io_drain_req() goes before checks for REQ_F_FAIL, which protect us from
submitting under-prepared request (e.g. failed in io_init_req(). Fail
such drained requests as well.

Fixes: a8295b982c46d ("io_uring: fix failed linkchain code logic")
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 fs/io_uring.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 6e07456d9842..2514adced460 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -6232,6 +6232,11 @@ static bool io_drain_req(struct io_kiocb *req)
 	int ret;
 	u32 seq;
 
+	if (req->flags & REQ_F_FAIL) {
+		io_req_complete_fail_submit(req);
+		return true;
+	}
+
 	/*
 	 * If we need to drain a request in the middle of a link, drain the
 	 * head request and the next request/link after the current link.
-- 
2.33.0

Re: [PATCH v2 0/2] fix failing request submission

[Jens Axboe]

On 8/31/21 7:13 AM, Pavel Begunkov wrote:
> Fix small problems with new link fail logic
> 
> v2: set REQ_F_LINK after clearing HARDLINK, leaking reqs otherwise (Hao)
> 
> Pavel Begunkov (2):
>   io_uring: fix queueing half-created requests
>   io_uring: don't submit half-prepared drain request
> 
>  fs/io_uring.c | 18 +++++++++++++++++-
>  1 file changed, 17 insertions(+), 1 deletion(-)

Applied, thanks.

-- 
Jens Axboe