linux-kernel - Re: [PATCH] bcache: revert replacing IS_ERR_OR_NULL with IS

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Message-Id: <640974BB-8D2A-4B64-B8F6-C59E931DDFE4@suse.de>
Date:   Sat, 25 Nov 2023 00:42:21 +0800
From:   Coly Li <colyli@...e.de>
To:     Jens Axboe <axboe@...nel.dk>
Cc:     Markus Weippert <markus@...mihesg.de>,
        Bcache Linux <linux-bcache@...r.kernel.org>,
        Thorsten Leemhuis <regressions@...mhuis.info>,
        Zheng Wang <zyytlz.wz@....com>, linux-kernel@...r.kernel.org,
        Stefan Förster <cite@...ertum.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>,
        Linux kernel regressions list <regressions@...ts.linux.dev>
Subject: Re: [PATCH] bcache: revert replacing IS_ERR_OR_NULL with IS_ERR



> 2023年11月25日 00:35，Jens Axboe <axboe@...nel.dk> 写道：
> 
> On 11/24/23 9:34 AM, Coly Li wrote:
>> 
>> 
>>> 2023?11?25? 00:31?Jens Axboe <axboe@...nel.dk> ???
>>> 
>>> On 11/24/23 9:29 AM, Coly Li wrote:
>>>> 
>>>> 
>>>>> 2023?11?24? 23:14?Markus Weippert <markus@...mihesg.de> ???
>>>>> 
>>>>> Commit 028ddcac477b ("bcache: Remove unnecessary NULL point check in
>>>>> node allocations") replaced IS_ERR_OR_NULL by IS_ERR. This leads to a
>>>>> NULL pointer dereference.
>>>>> 
>>>>> BUG: kernel NULL pointer dereference, address: 0000000000000080
>>>>> Call Trace:
>>>>> ? __die_body.cold+0x1a/0x1f
>>>>> ? page_fault_oops+0xd2/0x2b0
>>>>> ? exc_page_fault+0x70/0x170
>>>>> ? asm_exc_page_fault+0x22/0x30
>>>>> ? btree_node_free+0xf/0x160 [bcache]
>>>>> ? up_write+0x32/0x60
>>>>> btree_gc_coalesce+0x2aa/0x890 [bcache]
>>>>> ? bch_extent_bad+0x70/0x170 [bcache]
>>>>> btree_gc_recurse+0x130/0x390 [bcache]
>>>>> ? btree_gc_mark_node+0x72/0x230 [bcache]
>>>>> bch_btree_gc+0x5da/0x600 [bcache]
>>>>> ? cpuusage_read+0x10/0x10
>>>>> ? bch_btree_gc+0x600/0x600 [bcache]
>>>>> bch_gc_thread+0x135/0x180 [bcache]
>>>>> 
>>>>> The relevant code starts with:
>>>>> 
>>>>>  new_nodes[0] = NULL;
>>>>> 
>>>>>  for (i = 0; i < nodes; i++) {
>>>>>      if (__bch_keylist_realloc(&keylist, bkey_u64s(&r[i].b->key)))
>>>>>          goto out_nocoalesce;
>>>>>  // ...
>>>>> out_nocoalesce:
>>>>>  // ...
>>>>>  for (i = 0; i < nodes; i++)
>>>>>      if (!IS_ERR(new_nodes[i])) {  // IS_ERR_OR_NULL before
>>>>> 028ddcac477b
>>>>>          btree_node_free(new_nodes[i]);  // new_nodes[0] is NULL
>>>>>          rw_unlock(true, new_nodes[i]);
>>>>>      }
>>>>> 
>>>>> This patch replaces IS_ERR() by IS_ERR_OR_NULL() to fix this.
>>>>> 
>>>>> Fixes: 028ddcac477b ("bcache: Remove unnecessary NULL point check in
>>>>> node allocations")
>>>>> Link:
>>>>> https://lore.kernel.org/all/3DF4A87A-2AC1-4893-AE5F-E921478419A9@suse.de/
>>>>> Cc: stable@...r.kernel.org
>>>>> Cc: Zheng Wang <zyytlz.wz@....com>
>>>>> Cc: Coly Li <colyli@...e.de>
>>>>> Signed-off-by: Markus Weippert <markus@...mihesg.de>
>>>> 
>>>> Added into my for-next.  Thanks for patching up.
>>> 
>>> We should probably get this into the current release, rather than punt
>>> it to 6.8.
>> 
>> Yes, copied. So far I don?t have other bcache patches for 6.7, I feel
>> I might be redundant if I send you another for -rc4 series with this
>> single patch.
>> 
>> Could you please directly take it into -rc4?
> 
> Sure, I'll just grab it as-is.

Thanks for doing this.

Coly Li