From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 26F9A5221E0; Wed, 30 Sep 2026 17:55:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790790959; cv=none; b=t52ENzyJHJTQ2/1Wkt83PD9Km+M7sYJSXPDLNnFzODi/uipvZR2QB2JFKJbxKKibR1WEcgN4nStolrxws2XmgqMACXl33e39tADVonB+oQrUSu+u9PRtHQLWKaSssMQTkK7in1EcEbv9qmyrb5/NDcfiYJb0tGTbs9GYX324OBc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790790959; c=relaxed/simple; bh=Kn9uiabDUtE1nDNmvkQzGF27lGageMqDk50g9QDSOGg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=spLy/uRp48loymfWpaEKQ4xDD9MOzaLfMyrcVcoxVPQJkB5UL88BST5nMp+beMdcTS2rhnf0b/KCTa+YK6bvxJVLFdARg/vgASg75wh6dlLXIKvTiduw0APlfoO1WcPl8QPnyhID8Z+3dig/Irhj+kUW9jg9U0J9ZPnl8VyKFws= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=DV/Mls3Q; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="DV/Mls3Q" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 566661F000FF; Wed, 30 Sep 2026 17:55:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1790790957; bh=fotyLroRjX8QK0RwNw0i90+wSUUBYl0F14gr6bO4owE=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=DV/Mls3QWZBb0Oc0pUtez7sWMC/0yWOtGMAHUod1fP/g9DlyQ9yiXLdnlpXcKaDkx LJuOnrz3MAOJPR0KsW1nhmvO0EIlEwXdbSInuFaI07FExuizw/F5gSMI6XQFg49+W+ tFxKICAmGS7pU/Nl1ucZtbgRXWS9Z+bnV808e2GU= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, ZhengYuan Huang , David Sterba , Sasha Levin Subject: [PATCH 5.15 127/752] btrfs: balance: fix potential bg lookup failure in btrfs_may_alloc_data_chunk() Date: Wed, 30 Sep 2026 17:19:57 +0200 Message-ID: <20260930152400.927711142@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260930152358.131179731@linuxfoundation.org> References: <20260930152358.131179731@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 5.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: ZhengYuan Huang [ Upstream commit 18d32b0013efba19f7ad3e5b08d7aee813d604a6 ] [BUG] Running btrfs balance can trigger a null-ptr-deref before relocating a data chunk when metadata corruption leaves a chunk in the chunk tree without a corresponding block group in the in-memory cache: KASAN: null-ptr-deref in range [0x0000000000000088-0x000000000000008f] RIP: 0010:btrfs_may_alloc_data_chunk+0x40/0x1c0 fs/btrfs/volumes.c:3601 Call Trace: __btrfs_balance fs/btrfs/volumes.c:4217 [inline] btrfs_balance+0x2516/0x42b0 fs/btrfs/volumes.c:4604 btrfs_ioctl_balance fs/btrfs/ioctl.c:3577 [inline] btrfs_ioctl+0x25cf/0x5b90 fs/btrfs/ioctl.c:5313 ... [CAUSE] __btrfs_balance() iterates the on-disk chunk tree and passes the chunk logical bytenr to btrfs_may_alloc_data_chunk() before relocating a data chunk. That helper then queries the in-memory block group cache: cache = btrfs_lookup_block_group(fs_info, chunk_offset); chunk_type = cache->flags; /* cache may be NULL */ A corrupt image can contain a chunk item whose matching block group item is missing, so no block group is ever inserted into the cache. In that case btrfs_lookup_block_group() returns NULL. The code only guards this with ASSERT(cache), which becomes a no-op when CONFIG_BTRFS_ASSERT is disabled. The subsequent dereference of cache->flags therefore crashes the kernel. [FIX] Add a NULL check after btrfs_lookup_block_group() in btrfs_may_alloc_data_chunk() and print and error message for clarity. Signed-off-by: ZhengYuan Huang Reviewed-by: David Sterba Signed-off-by: David Sterba Signed-off-by: Sasha Levin --- fs/btrfs/volumes.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index 9ab226814cfde..459dd6da41af5 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -3476,7 +3476,11 @@ static int btrfs_may_alloc_data_chunk(struct btrfs_fs_info *fs_info, u64 chunk_type; cache = btrfs_lookup_block_group(fs_info, chunk_offset); - ASSERT(cache); + if (unlikely(!cache)) { + btrfs_err(fs_info, "balance: chunk at bytenr %llu has no corresponding block group", + chunk_offset); + return -EUCLEAN; + } chunk_type = cache->flags; btrfs_put_block_group(cache); -- 2.53.0