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

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Message-ID: <54706535-208b-43b5-814f-570ffa7b29bb@kernel.dk>
Date:   Fri, 24 Nov 2023 09:31:05 -0700
From:   Jens Axboe <axboe@...nel.dk>
To:     Coly Li <colyli@...e.de>, Markus Weippert <markus@...mihesg.de>
Cc:     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

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.

-- 
Jens Axboe