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linux-stable/io_uring
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Gabriel Krisman Bertazi 67c16c9415 io_uring: Don't set affinity on a dying sqpoll thread 
commit bd6fc5da4c upstream.

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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
 		2023-09-13 09:48:40 +02:00
..
Makefile
…
advise.c io_uring: always go async for unsupported fadvise flags 2023-01-29 15:18:26 -07:00
advise.h
…
alloc_cache.h io_uring/rsrc: consolidate node caching 2023-04-12 12:09:41 -06:00
cancel.c io_uring/cancel: re-grab ctx mutex after finishing wait 2022-12-21 13:31:40 -07:00
cancel.h
…
epoll.c io_uring: undeprecate epoll_ctl support 2023-05-26 20:22:41 -06:00
epoll.h
…
fdinfo.c capability: just use a 'u64' instead of a 'u32[2]' array 2023-03-01 10:01:22 -08:00
fdinfo.h
…
filetable.c io_uring/rsrc: merge nodes and io_rsrc_put 2023-04-18 19:38:26 -06:00
filetable.h io_uring: kill hot path fixed file bitmap debug checks 2022-10-16 17:07:53 -06:00
fs.c io_uring: for requests that require async, force it 2023-01-29 15:18:26 -07:00
fs.h
…
io-wq.c io_uring: break out of iowq iopoll on teardown 2023-09-13 09:48:39 +02:00
io-wq.h io_uring: break out of iowq iopoll on teardown 2023-09-13 09:48:39 +02:00
io_uring.c io_uring: break out of iowq iopoll on teardown 2023-09-13 09:48:39 +02:00
io_uring.h io_uring: fix false positive KASAN warnings 2023-09-13 09:48:39 +02:00
kbuf.c for-6.4/io_uring-2023-04-21 2023-04-26 12:40:31 -07:00
kbuf.h io_uring: add support for user mapped provided buffer ring 2023-04-03 07:14:21 -06:00
msg_ring.c io_uring/msg_ring: let target know allocated index 2023-03-16 07:16:56 -06:00
msg_ring.h io_uring: get rid of double locking 2022-12-07 06:47:13 -07:00
net.c io_uring/net: use the correct msghdr union member in io_sendmsg_copy_hdr 2023-06-21 07:34:17 -06:00
net.h io_uring: Add KASAN support for alloc_caches 2023-04-03 07:16:14 -06:00
nop.c
…
nop.h
…
notif.c io_uring/notif: add constant for ubuf_info flags 2023-04-15 14:21:04 -06:00
notif.h io_uring/notif: add constant for ubuf_info flags 2023-04-15 14:21:04 -06:00
opdef.c io_uring: Pass whole sqe to commands 2023-05-04 08:19:05 -06:00
opdef.h io_uring: Split io_issue_def struct 2023-01-29 15:17:41 -07:00
openclose.c io_uring: correct check for O_TMPFILE 2023-08-16 18:32:19 +02:00
openclose.h
…
poll.c io_uring/poll: serialize poll linked timer start with poll removal 2023-06-17 20:21:52 -06:00
poll.h io_uring/poll: allow some retries for poll triggering spuriously 2023-02-25 20:10:13 -07:00
refs.h
…
rsrc.c for-6.4/io_uring-2023-05-07 2023-05-07 10:00:09 -07:00
rsrc.h io_uring/rsrc: disassociate nodes and rsrc_data 2023-04-18 19:38:26 -06:00
rw.c for-6.4/block-2023-04-21 2023-04-26 12:52:58 -07:00
rw.h io_uring/rw: don't lose partial IO result on fail 2022-09-21 13:15:02 -06:00
slist.h io_uring: silence variable ‘prev’ set but not used warning 2023-03-09 10:10:58 -07:00
splice.c io_uring: for requests that require async, force it 2023-01-29 15:18:26 -07:00
splice.h
…
sqpoll.c io_uring: Don't set affinity on a dying sqpoll thread 2023-09-13 09:48:40 +02:00
sqpoll.h io_uring/sqpoll: fix io-wq affinity when IORING_SETUP_SQPOLL is used 2023-09-13 09:48:39 +02:00
statx.c io_uring: for requests that require async, force it 2023-01-29 15:18:26 -07:00
statx.h
…
sync.c io_uring: for requests that require async, force it 2023-01-29 15:18:26 -07:00
sync.h
…
tctx.c io_uring: rename 'in_idle' to 'in_cancel' 2023-02-22 09:57:23 -07:00
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 12:14:26 +02:00
timeout.h io_uring: remove unused return from io_disarm_next 2022-09-21 13:15:01 -06:00
uring_cmd.c io_uring: Remove unnecessary BUILD_BUG_ON 2023-05-04 08:19:05 -06:00
uring_cmd.h io_uring: Remove unnecessary BUILD_BUG_ON 2023-05-04 08:19:05 -06:00
xattr.c io_uring: for requests that require async, force it 2023-01-29 15:18:26 -07:00
xattr.h
…