Hello,
syzbot found the following issue on:
HEAD commit: 29c395c7 Merge tag 'x86-entry-2021-02-24' of git://git.ker..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11cd05cad00000
kernel config: https://syzkaller.appspot.com/x/.config?x=c581c545cb4ffac7
dashboard link: https://syzkaller.appspot.com/bug?extid=a157ac7c03a56397f553
compiler: Debian clang version 11.0.1-2
Unfortunately, I don't have any reproducer for this issue yet.
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: [email protected]
==================================================================
BUG: KASAN: use-after-free in __tctx_task_work fs/io_uring.c:2217 [inline]
BUG: KASAN: use-after-free in tctx_task_work+0x238/0x280 fs/io_uring.c:2230
Read of size 4 at addr ffff88802178e3f0 by task syz-executor.2/12656
CPU: 1 PID: 12656 Comm: syz-executor.2 Not tainted 5.11.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:79 [inline]
dump_stack+0x125/0x19e lib/dump_stack.c:120
print_address_description+0x5f/0x3a0 mm/kasan/report.c:230
__kasan_report mm/kasan/report.c:397 [inline]
kasan_report+0x15e/0x200 mm/kasan/report.c:414
__tctx_task_work fs/io_uring.c:2217 [inline]
tctx_task_work+0x238/0x280 fs/io_uring.c:2230
task_work_run+0x146/0x1c0 kernel/task_work.c:140
exit_task_work include/linux/task_work.h:30 [inline]
do_exit+0x6e4/0x2380 kernel/exit.c:825
do_group_exit+0x168/0x2d0 kernel/exit.c:922
get_signal+0x1734/0x1ef0 kernel/signal.c:2773
arch_do_signal_or_restart+0x3c/0x610 arch/x86/kernel/signal.c:811
handle_signal_work kernel/entry/common.c:147 [inline]
exit_to_user_mode_loop kernel/entry/common.c:171 [inline]
exit_to_user_mode_prepare+0xac/0x1e0 kernel/entry/common.c:208
__syscall_exit_to_user_mode_work kernel/entry/common.c:290 [inline]
syscall_exit_to_user_mode+0x48/0x180 kernel/entry/common.c:301
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x465ef9
Code: Unable to access opcode bytes at RIP 0x465ecf.
RSP: 002b:00007f80563b5188 EFLAGS: 00000246 ORIG_RAX: 00000000000001aa
RAX: 0000000000000302 RBX: 000000000056c008 RCX: 0000000000465ef9
RDX: 0000000000000000 RSI: 0000000000000302 RDI: 0000000000000003
RBP: 00000000004bcd1c R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056c008
R13: 00007ffedb23021f R14: 00007f80563b5300 R15: 0000000000022000
Allocated by task 12638:
kasan_save_stack mm/kasan/common.c:38 [inline]
kasan_set_track mm/kasan/common.c:46 [inline]
set_alloc_info mm/kasan/common.c:400 [inline]
____kasan_kmalloc+0xbd/0xf0 mm/kasan/common.c:428
kasan_kmalloc include/linux/kasan.h:218 [inline]
kmem_cache_alloc_trace+0x205/0x300 mm/slub.c:2922
kmalloc include/linux/slab.h:554 [inline]
kzalloc include/linux/slab.h:684 [inline]
io_ring_ctx_alloc fs/io_uring.c:1316 [inline]
io_uring_create fs/io_uring.c:9745 [inline]
io_uring_setup fs/io_uring.c:9876 [inline]
__do_sys_io_uring_setup fs/io_uring.c:9882 [inline]
__se_sys_io_uring_setup+0x368/0x3140 fs/io_uring.c:9879
do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xae
Freed by task 54:
kasan_save_stack mm/kasan/common.c:38 [inline]
kasan_set_track+0x3d/0x70 mm/kasan/common.c:46
kasan_set_free_info+0x1f/0x40 mm/kasan/generic.c:356
____kasan_slab_free+0xd3/0x110 mm/kasan/common.c:361
kasan_slab_free include/linux/kasan.h:191 [inline]
slab_free_hook mm/slub.c:1561 [inline]
slab_free_freelist_hook+0xdd/0x1b0 mm/slub.c:1594
slab_free mm/slub.c:3146 [inline]
kfree+0xcf/0x2b0 mm/slub.c:4182
process_one_work+0x789/0xfd0 kernel/workqueue.c:2275
worker_thread+0xac1/0x1300 kernel/workqueue.c:2421
kthread+0x39a/0x3c0 kernel/kthread.c:292
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294
Last potentially related work creation:
kasan_save_stack+0x27/0x50 mm/kasan/common.c:38
kasan_record_aux_stack+0xcc/0x100 mm/kasan/generic.c:344
insert_work+0x54/0x400 kernel/workqueue.c:1331
__queue_work+0x97f/0xcc0 kernel/workqueue.c:1497
queue_work_on+0xb5/0x100 kernel/workqueue.c:1524
io_uring_release+0x57/0x70 fs/io_uring.c:8895
__fput+0x352/0x7b0 fs/file_table.c:280
task_work_run+0x146/0x1c0 kernel/task_work.c:140
exit_task_work include/linux/task_work.h:30 [inline]
do_exit+0x6e4/0x2380 kernel/exit.c:825
do_group_exit+0x168/0x2d0 kernel/exit.c:922
get_signal+0x1734/0x1ef0 kernel/signal.c:2773
arch_do_signal_or_restart+0x3c/0x610 arch/x86/kernel/signal.c:811
handle_signal_work kernel/entry/common.c:147 [inline]
exit_to_user_mode_loop kernel/entry/common.c:171 [inline]
exit_to_user_mode_prepare+0xac/0x1e0 kernel/entry/common.c:208
__syscall_exit_to_user_mode_work kernel/entry/common.c:290 [inline]
syscall_exit_to_user_mode+0x48/0x180 kernel/entry/common.c:301
entry_SYSCALL_64_after_hwframe+0x44/0xae
The buggy address belongs to the object at ffff88802178e000
which belongs to the cache kmalloc-4k of size 4096
The buggy address is located 1008 bytes inside of
4096-byte region [ffff88802178e000, ffff88802178f000)
The buggy address belongs to the page:
page:00000000f7d94ef1 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x21788
head:00000000f7d94ef1 order:3 compound_mapcount:0 compound_pincount:0
flags: 0xfff00000010200(slab|head)
raw: 00fff00000010200 dead000000000100 dead000000000122 ffff888011042140
raw: 0000000000000000 0000000000040004 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
Memory state around the buggy address:
ffff88802178e280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88802178e300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88802178e380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88802178e400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88802178e480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
---
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On 2/28/21 2:59 AM, syzbot wrote:
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: 29c395c7 Merge tag 'x86-entry-2021-02-24' of git://git.ker..
> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=11cd05cad00000
> kernel config: https://syzkaller.appspot.com/x/.config?x=c581c545cb4ffac7
> dashboard link: https://syzkaller.appspot.com/bug?extid=a157ac7c03a56397f553
> compiler: Debian clang version 11.0.1-2
>
> Unfortunately, I don't have any reproducer for this issue yet.
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: [email protected]
>
> ==================================================================
> BUG: KASAN: use-after-free in __tctx_task_work fs/io_uring.c:2217 [inline]
> BUG: KASAN: use-after-free in tctx_task_work+0x238/0x280 fs/io_uring.c:2230
> Read of size 4 at addr ffff88802178e3f0 by task syz-executor.2/12656
This should fix it.
commit adc34362605c08e622c0750ae3377ed03637abd1
Author: Jens Axboe <[email protected]>
Date: Sun Feb 28 09:59:26 2021 -0700
io_uring: don't attempt to re-flush completions
If 'node' is NULL, there are no more completions to flush after doing
this round. And since the req flushing will put ctx references, it's
quite possible that the ctx is gone after the flush. Don't dereference
it unless we know we have more to flush.
Fixes: 65453d1efbd2 ("io_uring: enable req cache for task_work items")
Reported-by: [email protected]
Signed-off-by: Jens Axboe <[email protected]>
diff --git a/fs/io_uring.c b/fs/io_uring.c
index 87e8e40b566e..9db79d4b0827 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -1829,7 +1829,7 @@ static bool __tctx_task_work(struct io_uring_task *tctx)
mutex_lock(&ctx->uring_lock);
io_submit_flush_completions(&ctx->submit_state.comp, ctx);
mutex_unlock(&ctx->uring_lock);
- ctx = this_ctx;
+ ctx = node ? this_ctx : NULL;
}
}
--
Jens Axboe