CVE-2026-97416

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> btrfs: balance: fix potential bg lookup failure in btrfs_may_alloc_data_chunk()<br /> <br /> [BUG]<br /> Running btrfs balance can trigger a null-ptr-deref before relocating a<br /> data chunk when metadata corruption leaves a chunk in the chunk tree<br /> without a corresponding block group in the in-memory cache:<br /> <br /> KASAN: null-ptr-deref in range [0x0000000000000088-0x000000000000008f]<br /> RIP: 0010:btrfs_may_alloc_data_chunk+0x40/0x1c0 fs/btrfs/volumes.c:3601<br /> Call Trace:<br /> __btrfs_balance fs/btrfs/volumes.c:4217 [inline]<br /> btrfs_balance+0x2516/0x42b0 fs/btrfs/volumes.c:4604<br /> btrfs_ioctl_balance fs/btrfs/ioctl.c:3577 [inline]<br /> btrfs_ioctl+0x25cf/0x5b90 fs/btrfs/ioctl.c:5313<br /> ...<br /> <br /> [CAUSE]<br /> __btrfs_balance() iterates the on-disk chunk tree and passes the chunk<br /> logical bytenr to btrfs_may_alloc_data_chunk() before relocating a data<br /> chunk. That helper then queries the in-memory block group cache:<br /> <br /> cache = btrfs_lookup_block_group(fs_info, chunk_offset);<br /> chunk_type = cache-&gt;flags; /* cache may be NULL */<br /> <br /> A corrupt image can contain a chunk item whose matching block group<br /> item is missing, so no block group is ever inserted into the cache. In<br /> that case btrfs_lookup_block_group() returns NULL.<br /> <br /> The code only guards this with ASSERT(cache), which becomes a no-op when<br /> CONFIG_BTRFS_ASSERT is disabled. The subsequent dereference of<br /> cache-&gt;flags therefore crashes the kernel.<br /> <br /> [FIX]<br /> Add a NULL check after btrfs_lookup_block_group() in<br /> btrfs_may_alloc_data_chunk() and print and error message for clarity.