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 3ECF13CE4B2; Thu, 17 Sep 2026 17:58:13 +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=1789667894; cv=none; b=tGNq86Gf2DXLQ/rRpAVueETVX7KsxKHCdA2IGEXPybjMJUtOf1Xl4h5DpAnnDZ+3vgP1tUAVWRa0vzE50xno58Pwu605noRf/uSsMuN4PyW5dPiOUSsYeGv417I2jLV4m8vg3ZBZbm5qBZnYmrerQWSUKrPm/uuBzoJg418paVQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789667894; c=relaxed/simple; bh=18T7EYfkWJbbtiBHpVmQJvy4nsjYy6iQvqB6kAbnbUg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=hjIRrCdKnPuAFJ69nJ/ryGhrbSAaPnxzV7gVo44yn3+f7aJ1xSTZUI0vhxzmnargkF0ljCYmLJjFa8E0NJBw+dL153OzM4bnRyFLZMtm4U4nKdRV+6RhKwMUqLee/ElhwMS6TWJymTSzdgF+i8b9mmw9LqFXCMj1qsguQDxBbCY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=p/so6NyY; 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="p/so6NyY" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 856DD1F000FF; Thu, 17 Sep 2026 17:58:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1789667893; bh=JnfOf/jjEDIo5b/JuVJA5R4GPAbrARm0HBJBIlArI7o=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=p/so6NyYG3fLXR5PDgdI2vwJuNq7O4LdGWofjEnbEEBXJ/hytJa4mvmo/pIf4tXno t4OMRlxxlZ2OmI54FqtFcNkY23fKGHwfPOzsK9aZ7i3ufhwSWL8Alde+LDFj7UkgF6 MPs0/miD/aXVKpXxQ7Xedmj0aNxlo6FTBhZbOqlY= 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 6.12 0243/1102] btrfs: balance: fix potential bg lookup failure in btrfs_may_alloc_data_chunk() Date: Thu, 17 Sep 2026 16:03:06 +0100 Message-ID: <20260917151545.692697214@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260917151539.408551884@linuxfoundation.org> References: <20260917151539.408551884@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 6.12-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 c53e7e5c9d426..df8ab91d3151f 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -3565,7 +3565,11 @@ 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