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linux-stable/io_uring
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Pavel Begunkov 3e8b9b06de io_uring: Don't set affinity on a dying sqpoll thread 
From: Gabriel Krisman Bertazi <krisman@suse.de>

[ upstream commit bd6fc5da4c ]

Syzbot reported a null-ptr-deref of sqd->thread inside
io_sqpoll_wq_cpu_affinity.  It turns out the sqd->thread can go away
from under us during io_uring_register, in case the process gets a
fatal signal during io_uring_register.

It is not particularly hard to hit the race, and while I am not sure
this is the exact case hit by syzbot, it solves it.  Finally, checking
->thread is enough to close the race because we locked sqd while
"parking" the thread, thus preventing it from going away.

I reproduced it fairly consistently with a program that does:

int main(void) {
  ...
  io_uring_queue_init(RING_LEN, &ring1, IORING_SETUP_SQPOLL);
  while (1) {
    io_uring_register_iowq_aff(ring, 1, &mask);
  }
}

Executed in a loop with timeout to trigger SIGTERM:
  while true; do timeout 1 /a.out ; done

This will hit the following BUG() in very few attempts.

BUG: kernel NULL pointer dereference, address: 00000000000007a8
PGD 800000010e949067 P4D 800000010e949067 PUD 10e46e067 PMD 0
Oops: 0000 [#1] PREEMPT SMP PTI
CPU: 0 PID: 15715 Comm: dead-sqpoll Not tainted 6.5.0-rc7-next-20230825-g193296236fa0-dirty #23
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015
RIP: 0010:io_sqpoll_wq_cpu_affinity+0x27/0x70
Code: 90 90 90 0f 1f 44 00 00 55 53 48 8b 9f 98 03 00 00 48 85 db 74 4f
48 89 df 48 89 f5 e8 e2 f8 ff ff 48 8b 43 38 48 85 c0 74 22 <48> 8b b8
a8 07 00 00 48 89 ee e8 ba b1 00 00 48 89 df 89 c5 e8 70
RSP: 0018:ffffb04040ea7e70 EFLAGS: 00010282
RAX: 0000000000000000 RBX: ffff93c010749e40 RCX: 0000000000000001
RDX: 0000000000000000 RSI: ffffffffa7653331 RDI: 00000000ffffffff
RBP: ffffb04040ea7eb8 R08: 0000000000000000 R09: c0000000ffffdfff
R10: ffff93c01141b600 R11: ffffb04040ea7d18 R12: ffff93c00ea74840
R13: 0000000000000011 R14: 0000000000000000 R15: ffff93c00ea74800
FS:  00007fb7c276ab80(0000) GS:ffff93c36f200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000000007a8 CR3: 0000000111634003 CR4: 0000000000370ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 ? __die_body+0x1a/0x60
 ? page_fault_oops+0x154/0x440
 ? do_user_addr_fault+0x174/0x7b0
 ? exc_page_fault+0x63/0x140
 ? asm_exc_page_fault+0x22/0x30
 ? io_sqpoll_wq_cpu_affinity+0x27/0x70
 __io_register_iowq_aff+0x2b/0x60
 __io_uring_register+0x614/0xa70
 __x64_sys_io_uring_register+0xaa/0x1a0
 do_syscall_64+0x3a/0x90
 entry_SYSCALL_64_after_hwframe+0x6e/0xd8
RIP: 0033:0x7fb7c226fec9
Code: 2e 00 b8 ca 00 00 00 0f 05 eb a5 66 0f 1f 44 00 00 48 89 f8 48 89
f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01
f0 ff ff 73 01 c3 48 8b 0d 97 7f 2d 00 f7 d8 64 89 01 48
RSP: 002b:00007ffe2c0674f8 EFLAGS: 00000246 ORIG_RAX: 00000000000001ab
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fb7c226fec9
RDX: 00007ffe2c067530 RSI: 0000000000000011 RDI: 0000000000000003
RBP: 00007ffe2c0675d0 R08: 00007ffe2c067550 R09: 00007ffe2c067550
R10: 0000000000000001 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffe2c067750 R14: 0000000000000000 R15: 0000000000000000
 </TASK>
Modules linked in:
CR2: 00000000000007a8
---[ end trace 0000000000000000 ]---

Reported-by: syzbot+c74fea926a78b8a91042@syzkaller.appspotmail.com
Fixes: ebdfefc09c ("io_uring/sqpoll: fix io-wq affinity when IORING_SETUP_SQPOLL is used")
Signed-off-by: Gabriel Krisman Bertazi <krisman@suse.de>
Link: https://lore.kernel.org/r/87v8cybuo6.fsf@suse.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2023-09-19 12:27:54 +02:00
..
advise.c io_uring: make io_kiocb_to_cmd() typesafe 2022-08-12 17:01:00 -06:00
advise.h
alloc_cache.h io_uring: fix poll/netmsg alloc caches 2023-04-06 12:10:52 +02:00
cancel.c io_uring/cancel: re-grab ctx mutex after finishing wait 2023-01-12 12:02:38 +01:00
cancel.h
epoll.c io_uring: undeprecate epoll_ctl support 2023-06-09 10:34:23 +02:00
epoll.h
fdinfo.c io_uring/fdinfo: include locked hash table in fdinfo output 2023-01-18 11:58:15 +01:00
fdinfo.h
filetable.c io_uring/rsrc: fix null-ptr-deref in io_file_bitmap_get() 2023-03-30 12:49:25 +02:00
filetable.h io_uring: kill hot path fixed file bitmap debug checks 2022-10-16 17:07:53 -06:00
fs.c io_uring: make io_kiocb_to_cmd() typesafe 2022-08-12 17:01:00 -06:00
fs.h
io-wq.c io_uring/sqpoll: fix io-wq affinity when IORING_SETUP_SQPOLL is used 2023-09-19 12:27:54 +02:00
io-wq.h io_uring/sqpoll: fix io-wq affinity when IORING_SETUP_SQPOLL is used 2023-09-19 12:27:54 +02:00
io_uring.c io_uring/sqpoll: fix io-wq affinity when IORING_SETUP_SQPOLL is used 2023-09-19 12:27:54 +02:00
io_uring.h io_uring: mark task TASK_RUNNING before handling resume/task work 2023-03-10 09:34:07 +01:00
kbuf.c io_uring: fix memory leak when removing provided buffers 2023-04-13 16:55:31 +02:00
kbuf.h io_uring: allow buffer recycling in READV 2022-09-21 10:30:43 -06:00
Makefile
msg_ring.c io_uring/msg_ring: fix missing lock on overflow for IOPOLL 2023-08-30 16:11:05 +02:00
msg_ring.h io_uring: get rid of double locking 2023-08-30 16:11:04 +02:00
net.c io_uring/net: don't overflow multishot accept 2023-09-19 12:27:54 +02:00
net.h io_uring/net: zerocopy sendmsg 2022-09-21 13:15:02 -06:00
nop.c
nop.h
notif.c io_uring/net: introduce IORING_SEND_ZC_REPORT_USAGE flag 2022-12-31 13:33:11 +01:00
notif.h io_uring/net: introduce IORING_SEND_ZC_REPORT_USAGE flag 2022-12-31 13:33:11 +01:00
opdef.c io_uring: get rid of double locking 2023-08-30 16:11:04 +02:00
opdef.h io_uring: dont remove file from msg_ring reqs 2022-12-31 13:33:12 +01:00
openclose.c io_uring: correct check for O_TMPFILE 2023-08-16 18:27:24 +02:00
openclose.h
poll.c io_uring: always lock in io_apoll_task_func 2023-09-19 12:27:54 +02:00
poll.h io_uring/poll: allow some retries for poll triggering spuriously 2023-03-11 13:55:43 +01:00
refs.h
rsrc.c io_uring/rsrc: use nospec'ed indexes 2023-05-11 23:03:24 +09:00
rsrc.h io_uring/rsrc: fix rogue rsrc node grabbing 2023-04-06 12:10:51 +02:00
rw.c use less confusing names for iov_iter direction initializers 2023-02-09 11:28:04 +01:00
rw.h io_uring/rw: don't lose partial IO result on fail 2022-09-21 13:15:02 -06:00
slist.h
splice.c io_uring: make io_kiocb_to_cmd() typesafe 2022-08-12 17:01:00 -06:00
splice.h
sqpoll.c io_uring: Don't set affinity on a dying sqpoll thread 2023-09-19 12:27:54 +02:00
sqpoll.h io_uring/sqpoll: fix io-wq affinity when IORING_SETUP_SQPOLL is used 2023-09-19 12:27:54 +02:00
statx.c io_uring: make io_kiocb_to_cmd() typesafe 2022-08-12 17:01:00 -06:00
statx.h
sync.c io_uring: make io_kiocb_to_cmd() typesafe 2022-08-12 17:01:00 -06:00
sync.h
tctx.c io_uring: remove io_register_submitter 2022-10-07 12:25:30 -06:00
tctx.h io_uring: simplify __io_uring_add_tctx_node 2022-10-07 12:25:30 -06:00
timeout.c io_uring: annotate offset timeout races 2023-08-11 12:08:24 +02:00
timeout.h io_uring: remove unused return from io_disarm_next 2022-09-21 13:15:01 -06:00
uring_cmd.c block/io_uring: pass in issue_flags for uring_cmd task_work handling 2023-04-06 12:10:51 +02:00
uring_cmd.h
xattr.c __io_setxattr(): constify path 2022-09-01 17:39:05 -04:00
xattr.h