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

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Message-Id: <B68E455A-D6EB-4BB9-BD60-F2F8C3C8C21A@suse.de>
Date:   Sat, 25 Nov 2023 00:29:12 +0800
From:   Coly Li <colyli@...e.de>
To:     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>,
        Jens Axboe <axboe@...nel.dk>,
        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24日 23:14，Markus Weippert <markus@...mihesg.de> 写道：
> 
> 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.

Coly Li


> 
> ---
> drivers/md/bcache/btree.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c
> index de3019972..261596791 100644
> --- a/drivers/md/bcache/btree.c
> +++ b/drivers/md/bcache/btree.c
> @@ -1522,7 +1522,7 @@ static int btree_gc_coalesce(struct btree *b,
> struct btree_op *op,
>        bch_keylist_free(&keylist);
> 
>        for (i = 0; i < nodes; i++)
> -               if (!IS_ERR(new_nodes[i])) {
> +               if (!IS_ERR_OR_NULL(new_nodes[i])) {
>                        btree_node_free(new_nodes[i]);
>                        rw_unlock(true, new_nodes[i]);
>                }
> --