Stack corruption in bch2_nocow_write

[Daniel J Blueman]

Hi Kent et al,

On Linux 6.7-rc7 from bcachefs master SHA f3608cbdfd built with UBSAN
[1], with a crafted workload [2] I'm able to trigger stack corruption
in bch2_nocow_write [3].

Let me know if you can't reproduce it and I'll check reproducibility
on another platform, and let me know for any patch testing.

Reported-by: Daniel J Blueman <daniel@xxxxxxxxx>

Thanks,
  Daniel

-- [1] https://pastebin.com/WrhtGzck

-- [2]

modprobe brd rd_size=536870912 rd_nr=7
bcachefs format -f --nocow --foreground_target=/dev/ram4
--promote_target=/dev/ram5 /dev/ram1 /dev/ram2 /dev/ram5 /dev/ram0
/dev/ram4 /dev/ram6 /dev/ram3
mount -t bcachefs
/dev/ram1:/dev/ram2:/dev/ram5:/dev/ram0:/dev/ram4:/dev/ram6:/dev/ram3
/mnt
fio --group_reporting --ioengine=io_uring --directory=/mnt --size=16m
--time_based --runtime=60s --iodepth=256 --verify_async=8 --bs=4k-64k
--norandommap --random_distribution=zipf:0.5 --numjobs=16 --rw=randrw
--name=A --direct=1 --name=B --direct=0 >/dev/null &
sleep 10
bcachefs device offline /dev/ram5

-- [3]

================================================================================
UBSAN: array-index-out-of-bounds in fs/bcachefs/io_write.c:1258:11
index 4 is out of range for type '<unknown> [4]'
================================================================================
================================================================================
UBSAN: array-index-out-of-bounds in fs/bcachefs/io_write.c:1259:11
index 4 is out of range for type '<unknown> [4]'
================================================================================
================================================================================
UBSAN: array-index-out-of-bounds in fs/bcachefs/io_write.c:1262:30
index 4 is out of range for type '<unknown> [4]'
================================================================================
================================================================================
UBSAN: array-index-out-of-bounds in fs/bcachefs/io_write.c:1260:11
index 4 is out of range for type '<unknown> [4]'
================================================================================
================================================================================
UBSAN: array-index-out-of-bounds in fs/bcachefs/io_write.c:1264:4
index 4 is out of range for type '<unknown> [4]'
================================================================================
================================================================================
UBSAN: array-index-out-of-bounds in fs/bcachefs/io_write.c:1284:55
index 4 is out of range for type '<unknown> [4]'
================================================================================
================================================================================
UBSAN: array-index-out-of-bounds in fs/bcachefs/io_write.c:1285:41
index 4 is out of range for type '<unknown> [4]'
================================================================================
================================================================================
UBSAN: array-index-out-of-bounds in fs/bcachefs/io_write.c:1289:29
index 4 is out of range for type '<unknown> [4]'
================================================================================
================================================================================
UBSAN: array-index-out-of-bounds in fs/bcachefs/io_write.c:1293:67
index 4 is out of range for type '<unknown> [4]'
================================================================================
================================================================================
UBSAN: array-index-out-of-bounds in fs/bcachefs/io_write.c:1293:45
index 4 is out of range for type '<unknown> [4]'
================================================================================
Kernel panic - not syncing: stack-protector: Kernel stack is corrupted
in: bch2_nocow_write (fs/bcachefs/io_write.c:1284)
CPU: 29 PID: 4362 Comm: iou-wrk-3332 Not tainted 6.7.0-rc7+ #25
Hardware name: Supermicro AS -3014TS-i/H12SSL-i, BIOS 2.5 09/08/2022
Call Trace:
<TASK>
dump_stack_lvl (lib/dump_stack.c:107)
dump_stack (lib/dump_stack.c:114)
panic (kernel/panic.c:344)
? srso_alias_return_thunk (arch/x86/lib/retpoline.S:181)
? bch2_nocow_write (fs/bcachefs/io_write.c:1284)
__stack_chk_fail (??:?)
bch2_nocow_write (fs/bcachefs/io_write.c:1284)
? __lock_acquire (kernel/locking/lockdep.c:4599 (discriminator 1)
kernel/locking/lockdep.c:5091 (discriminator 1))
? srso_alias_return_thunk (arch/x86/lib/retpoline.S:181)
? lock_release (kernel/locking/lockdep.c:5430 kernel/locking/lockdep.c:5774)
? bch2_nocow_write (fs/bcachefs/bcachefs.h:1220 (discriminator 3)
fs/bcachefs/btree_iter.h:441 (discriminator 3)
fs/bcachefs/btree_iter.h:485 (discriminator 3)
fs/bcachefs/io_write.c:1231 (discriminator 3))
__bch2_write (fs/bcachefs/io_write.c:1393)
? __bch2_write (fs/bcachefs/io_write.c:1393)
? srso_alias_return_thunk (arch/x86/lib/retpoline.S:181)
? find_held_lock (kernel/locking/lockdep.c:5244 (discriminator 1))
? __bch2_increment_clock (fs/bcachefs/clock.c:153)
? srso_alias_return_thunk (arch/x86/lib/retpoline.S:181)
? lock_release (kernel/locking/lockdep.c:5430 kernel/locking/lockdep.c:5774)
? find_held_lock (kernel/locking/lockdep.c:5244 (discriminator 1))
? srso_alias_return_thunk (arch/x86/lib/retpoline.S:181)
bch2_write (fs/bcachefs/io_write.c:1613)
? srso_alias_return_thunk (arch/x86/lib/retpoline.S:181)
? bch2_write (fs/bcachefs/io_write.c:1613)
bch2_direct_write (fs/bcachefs/fs-io-direct.c:528
fs/bcachefs/fs-io-direct.c:644)
? lock_acquire (kernel/locking/lockdep.c:467 (discriminator 4)
kernel/locking/lockdep.c:5756 (discriminator 4)
kernel/locking/lockdep.c:5719 (discriminator 4))
? __entry_text_end (??:?)
bch2_write_iter (fs/bcachefs/fs-io-buffered.c:1055)
? bch2_read_iter (fs/bcachefs/errcode.h:266 (discriminator 1)
fs/bcachefs/fs-io-direct.c:206 (discriminator 1))
? srso_alias_return_thunk (arch/x86/lib/retpoline.S:181)
? lock_acquire (kernel/locking/lockdep.c:467 (discriminator 4)
kernel/locking/lockdep.c:5756 (discriminator 4)
kernel/locking/lockdep.c:5719 (discriminator 4))
? srso_alias_return_thunk (arch/x86/lib/retpoline.S:181)
? find_held_lock (kernel/locking/lockdep.c:5244 (discriminator 1))
? srso_alias_return_thunk (arch/x86/lib/retpoline.S:181)
? lock_release (kernel/locking/lockdep.c:5430 kernel/locking/lockdep.c:5774)
io_write (./include/linux/fs.h:2020 io_uring/rw.c:1029)
io_issue_sqe (io_uring/io_uring.c:1888)
io_wq_submit_work (io_uring/io_uring.c:1969)
io_worker_handle_work (io_uring/io-wq.c:540 io_uring/io-wq.c:597)
io_wq_worker (io_uring/io-wq.c:258 io_uring/io-wq.c:648)
? srso_alias_return_thunk (arch/x86/lib/retpoline.S:181)
? lock_release (kernel/locking/lockdep.c:5430 kernel/locking/lockdep.c:5774)
? __pfx_io_wq_worker (io_uring/io-wq.c:627)
? srso_alias_return_thunk (arch/x86/lib/retpoline.S:181)
? trace_hardirqs_on (kernel/trace/trace_preemptirq.c:63)
? srso_alias_return_thunk (arch/x86/lib/retpoline.S:181)
? __pfx_io_wq_worker (io_uring/io-wq.c:627)
ret_from_fork (arch/x86/kernel/process.c:153)
? __pfx_io_wq_worker (io_uring/io-wq.c:627)
ret_from_fork_asm (arch/x86/entry/entry_64.S:250)
RIP: 0033:0x0
Code: Unable to access opcode bytes at 0xffffffffffffffd6.

Code starting with the faulting instruction
===========================================
RSP: 002b:0000000000000000 EFLAGS: 00000246 ORIG_RAX: 00000000000001aa
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000564239f39ea3
RDX: 0000000000000002 RSI: 0000000000000000 RDI: 0000000000000006
RBP: 0000000000000002 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000246 R12: 00007f1b2dfd25c0
R13: 0000000000000002 R14: 0000000000000002 R15: 000056423a4e7b20
</TASK>
Kernel Offset: disabled
---[ end Kernel panic - not syncing: stack-protector: Kernel stack is
corrupted in: bch2_nocow_write+0x13e9/0x1770 ]---
-- 
Daniel J Blueman