KASAN: invalid-free in io_req_caches_free

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 31caf8b2 Merge branch 'linus' of git://git.kernel.org/pub/..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15a8afa6d00000
kernel config: https://syzkaller.appspot.com/x/.config?x=5a8f3a57fabb4015
dashboard link: https://syzkaller.appspot.com/bug?extid=30b4936dcdb3aafa4fb4

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: syzbot+30b493...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: double-free or invalid-free in io_req_caches_free.constprop.0+0x3ce/0x530 fs/io_uring.c:8709

CPU: 1 PID: 243 Comm: kworker/u4:6 Not tainted 5.11.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: events_unbound io_ring_exit_work
Call Trace:
__dump_stack lib/dump_stack.c:79 [inline]
dump_stack+0xfa/0x151 lib/dump_stack.c:120
print_address_description.constprop.0.cold+0x5b/0x2c6 mm/kasan/report.c:230
kasan_report_invalid_free+0x51/0x80 mm/kasan/report.c:355
____kasan_slab_free+0xcc/0xe0 mm/kasan/common.c:341
kasan_slab_free include/linux/kasan.h:192 [inline]
__cache_free mm/slab.c:3424 [inline]
kmem_cache_free_bulk+0x4b/0x1b0 mm/slab.c:3744
io_req_caches_free.constprop.0+0x3ce/0x530 fs/io_uring.c:8709
io_ring_ctx_free fs/io_uring.c:8764 [inline]
io_ring_exit_work+0x518/0x6b0 fs/io_uring.c:8846
process_one_work+0x98d/0x1600 kernel/workqueue.c:2275
worker_thread+0x64c/0x1120 kernel/workqueue.c:2421
kthread+0x3b1/0x4a0 kernel/kthread.c:292
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

Allocated by task 11900:
kasan_save_stack+0x1b/0x40 mm/kasan/common.c:38
kasan_set_track mm/kasan/common.c:46 [inline]
set_alloc_info mm/kasan/common.c:401 [inline]
____kasan_kmalloc.constprop.0+0x7f/0xa0 mm/kasan/common.c:429
kasan_slab_alloc include/linux/kasan.h:209 [inline]
slab_post_alloc_hook mm/slab.h:512 [inline]
kmem_cache_alloc_bulk+0x2c2/0x460 mm/slab.c:3534
io_alloc_req fs/io_uring.c:2014 [inline]
io_submit_sqes+0x18e8/0x2b60 fs/io_uring.c:6915
__do_sys_io_uring_enter+0x1154/0x1f50 fs/io_uring.c:9454
do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xae

Freed by task 11900:
kasan_save_stack+0x1b/0x40 mm/kasan/common.c:38
kasan_set_track+0x1c/0x30 mm/kasan/common.c:46
kasan_set_free_info+0x20/0x30 mm/kasan/generic.c:356
____kasan_slab_free+0xb0/0xe0 mm/kasan/common.c:362
kasan_slab_free include/linux/kasan.h:192 [inline]
__cache_free mm/slab.c:3424 [inline]
kmem_cache_free_bulk+0x4b/0x1b0 mm/slab.c:3744
io_req_caches_free.constprop.0+0x3ce/0x530 fs/io_uring.c:8709
io_uring_flush+0x483/0x6e0 fs/io_uring.c:9237
filp_close+0xb4/0x170 fs/open.c:1286
close_files fs/file.c:403 [inline]
put_files_struct fs/file.c:418 [inline]
put_files_struct+0x1d0/0x350 fs/file.c:415
exit_files+0x7e/0xa0 fs/file.c:435
do_exit+0xc27/0x2ae0 kernel/exit.c:820
do_group_exit+0x125/0x310 kernel/exit.c:922
get_signal+0x42c/0x2100 kernel/signal.c:2773
arch_do_signal_or_restart+0x2a8/0x1eb0 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+0x148/0x250 kernel/entry/common.c:208
__syscall_exit_to_user_mode_work kernel/entry/common.c:290 [inline]
syscall_exit_to_user_mode+0x19/0x50 kernel/entry/common.c:301
entry_SYSCALL_64_after_hwframe+0x44/0xae

The buggy address belongs to the object at ffff888012eaae00
which belongs to the cache io_kiocb of size 208
The buggy address is located 0 bytes inside of
208-byte region [ffff888012eaae00, ffff888012eaaed0)
The buggy address belongs to the page:
page:0000000091458aed refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x12eaa
flags: 0xfff00000000200(slab)
raw: 00fff00000000200 ffff8880188dcd50 ffff8880188dcd50 ffff888141b4ff00
raw: 0000000000000000 ffff888012eaa040 000000010000000c 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff888012eaad00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888012eaad80: fb fb fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff888012eaae00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff888012eaae80: fb fb fb fb fb fb fb fb fb fb fc fc fc fc fc fc
ffff888012eaaf00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================


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[Hillf Danton]

Mon, 22 Feb 2021 01:44:21 -0800

Fix double free by reverting 41be53e94fb0 ("io_uring: kill cached
requests from exiting task closing the ring") - it ruins kworker's life.

--- x/fs/io_uring.c
+++ y/fs/io_uring.c
@@ -9234,7 +9234,6 @@ static int io_uring_flush(struct file *f

if (fatal_signal_pending(current) || (current->flags & PF_EXITING)) {
io_uring_cancel_task_requests(ctx, NULL);
- io_req_caches_free(ctx, current);
}

if (!tctx)

[Jens Axboe]

Already merged the right fix this morning:

https://git.kernel.dk/cgit/linux-block/commit/?h=for-5.12/io_uring&id=8e5c66c485a8af3f39a8b0358e9e09f002016d92

--
Jens Axboe