Re: [PATCH 6.1] closures: Change BUG_ON() to WARN_ON()

[Bin Lan <bin.lan.cn@windriver.com>]

On 11/21/2024 3:13 PM, Kent Overstreet wrote:
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> On Thu, Nov 21, 2024 at 02:46:07PM +0800, Bin Lan wrote:
>> From: Kent Overstreet <kent.overstreet@linux.dev>
>>
>> [ Upstream commit 339b84ab6b1d66900c27bd999271cb2ae40ce812 ]
>>
>> If a BUG_ON() can be hit in the wild, it shouldn't be a BUG_ON()
>>
>> For reference, this has popped up once in the CI, and we'll need more
>> info to debug it:
>>
>> 03240 ------------[ cut here ]------------
>> 03240 kernel BUG at lib/closure.c:21!
>> 03240 kernel BUG at lib/closure.c:21!
>> 03240 Internal error: Oops - BUG: 00000000f2000800 [#1] SMP
>> 03240 Modules linked in:
>> 03240 CPU: 15 PID: 40534 Comm: kworker/u80:1 Not tainted 6.10.0-rc4-ktest-ga56da69799bd #25570
>> 03240 Hardware name: linux,dummy-virt (DT)
>> 03240 Workqueue: btree_update btree_interior_update_work
>> 03240 pstate: 00001005 (nzcv daif -PAN -UAO -TCO -DIT +SSBS BTYPE=--)
>> 03240 pc : closure_put+0x224/0x2a0
>> 03240 lr : closure_put+0x24/0x2a0
>> 03240 sp : ffff0000d12071c0
>> 03240 x29: ffff0000d12071c0 x28: dfff800000000000 x27: ffff0000d1207360
>> 03240 x26: 0000000000000040 x25: 0000000000000040 x24: 0000000000000040
>> 03240 x23: ffff0000c1f20180 x22: 0000000000000000 x21: ffff0000c1f20168
>> 03240 x20: 0000000040000000 x19: ffff0000c1f20140 x18: 0000000000000001
>> 03240 x17: 0000000000003aa0 x16: 0000000000003ad0 x15: 1fffe0001c326974
>> 03240 x14: 0000000000000a1e x13: 0000000000000000 x12: 1fffe000183e402d
>> 03240 x11: ffff6000183e402d x10: dfff800000000000 x9 : ffff6000183e402e
>> 03240 x8 : 0000000000000001 x7 : 00009fffe7c1bfd3 x6 : ffff0000c1f2016b
>> 03240 x5 : ffff0000c1f20168 x4 : ffff6000183e402e x3 : ffff800081391954
>> 03240 x2 : 0000000000000001 x1 : 0000000000000000 x0 : 00000000a8000000
>> 03240 Call trace:
>> 03240  closure_put+0x224/0x2a0
>> 03240  bch2_check_for_deadlock+0x910/0x1028
>> 03240  bch2_six_check_for_deadlock+0x1c/0x30
>> 03240  six_lock_slowpath.isra.0+0x29c/0xed0
>> 03240  six_lock_ip_waiter+0xa8/0xf8
>> 03240  __bch2_btree_node_lock_write+0x14c/0x298
>> 03240  bch2_trans_lock_write+0x6d4/0xb10
>> 03240  __bch2_trans_commit+0x135c/0x5520
>> 03240  btree_interior_update_work+0x1248/0x1c10
>> 03240  process_scheduled_works+0x53c/0xd90
>> 03240  worker_thread+0x370/0x8c8
>> 03240  kthread+0x258/0x2e8
>> 03240  ret_from_fork+0x10/0x20
>> 03240 Code: aa1303e0 d63f0020 a94363f7 17ffff8c (d4210000)
>> 03240 ---[ end trace 0000000000000000 ]---
>> 03240 Kernel panic - not syncing: Oops - BUG: Fatal exception
>> 03240 SMP: stopping secondary CPUs
>> 03241 SMP: failed to stop secondary CPUs 13,15
>> 03241 Kernel Offset: disabled
>> 03241 CPU features: 0x00,00000003,80000008,4240500b
>> 03241 Memory Limit: none
>> 03241 ---[ end Kernel panic - not syncing: Oops - BUG: Fatal exception ]---
>> 03246 ========= FAILED TIMEOUT copygc_torture_no_checksum in 7200s
>>
>> Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
>> [ Resolve minor conflicts to fix CVE-2024-42252 ]
>> Signed-off-by: Bin Lan <bin.lan.cn@windriver.com>
> I don't think this is needed on 6.1, this came up in bcachefs where
> we're using closures for refcounting btree_trans objects, and there was
> a crazy bug in the debugfs code... fixed awhile ago
>
> harmless if you want it just in case, though
Since it is harmless, I think we apply this patch for v6.1.y to fix the 
CVE-2024-42252.

B.R.

Bin Lan
>> ---
>>   drivers/md/bcache/closure.c | 10 ++++++++--
>>   1 file changed, 8 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/md/bcache/closure.c b/drivers/md/bcache/closure.c
>> index d8d9394a6beb..18f21d4e9aaa 100644
>> --- a/drivers/md/bcache/closure.c
>> +++ b/drivers/md/bcache/closure.c
>> @@ -17,10 +17,16 @@ static inline void closure_put_after_sub(struct closure *cl, int flags)
>>   {
>>        int r = flags & CLOSURE_REMAINING_MASK;
>>
>> -     BUG_ON(flags & CLOSURE_GUARD_MASK);
>> -     BUG_ON(!r && (flags & ~CLOSURE_DESTRUCTOR));
>> +     if (WARN(flags & CLOSURE_GUARD_MASK,
>> +              "closure has guard bits set: %x (%u)",
>> +              flags & CLOSURE_GUARD_MASK, (unsigned) __fls(r)))
>> +             r &= ~CLOSURE_GUARD_MASK;
>>
>>        if (!r) {
>> +             WARN(flags & ~CLOSURE_DESTRUCTOR,
>> +                  "closure ref hit 0 with incorrect flags set: %x (%u)",
>> +                  flags & ~CLOSURE_DESTRUCTOR, (unsigned) __fls(flags));
>> +
>>                if (cl->fn && !(flags & CLOSURE_DESTRUCTOR)) {
>>                        atomic_set(&cl->remaining,
>>                                   CLOSURE_REMAINING_INITIALIZER);
>> --
>> 2.43.0
>>