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 81C8523ABBE; Wed, 30 Sep 2026 18:52:53 +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=1790794374; cv=none; b=NDASN6MmY1DmlZrtIr4ZX+bZuU0yKTH3zqDnDLMOlSrhgDtISAIT9mhpiRsWdnLJ6YRygA3IJ6SmCZmcv+iCk4fU63WwOp4HtarHxmkBPWPXqZiRPAUQGU/ezFii2qNy2ZLSG5h1v6T9eKZUTfgsTOo5wIXve2nuPsjNdzryvLE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790794374; c=relaxed/simple; bh=eSl5/7ROpP98vP1SOjEUr8ecDeAUydy8y6eqknz5wks=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=cPzHlPhzCu+tCDGYB4as2poWtBOp2ES20+7pfLNDqdW/exn0qISTEBljEzXHwi+fKOqqR39HuJ4ReWmZzUHuv8wzhoEIAERzJ1vhHoDaKbBXq4IoHcRUCWY4GkFY9frS17lxgUuGykZhf7uKRlAB8pTNgHHKfmhHyBApNLclhS0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=uYYvYSd0; 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="uYYvYSd0" Received: by smtp.kernel.org (Postfix) with ESMTPSA id DE96A1F00898; Wed, 30 Sep 2026 18:52:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1790794373; bh=ZGaQDO59WiUn/xcuZilScR6UHrAcI/WdsYa9LR+JrY0=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=uYYvYSd03qlUZqsZHVHrM9Atqs+Ft3xQuFCygLRgEmMzzzhBOg0rivaHsQCd5LUhC QtOWG8CBdZEeudYMEJYBS/HPyp91NNV8M+TfnR5pylvwzgH1/vCgWXMoXUgc5ZDhTx 7nsTI+bJeLp7DO8yGQ0UjtGpEO9NV56AGISyxz0U= 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 6.6 0187/1193] btrfs: balance: fix potential bg lookup failure in btrfs_may_alloc_data_chunk() Date: Wed, 30 Sep 2026 17:14:31 +0200 Message-ID: <20260930152438.348587610@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260930152434.301151190@linuxfoundation.org> References: <20260930152434.301151190@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 6.6-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 f5e4b8f3dcb7f..b72fc74f6298c 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -3466,7 +3466,11 @@ 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