In the Linux kernel, the following vulnerability has been resolved:

btrfs: add a sanity check for btrfs root in btrfs_search_slot()

Syzbot reports a null-ptr-deref in btrfs_search_slot().

The reproducer is using rescue=ibadroots, and the extent tree root is
corrupted thus the extent tree is NULL.

When scrub tries to search the extent tree to gather the needed extent
info, btrfs_search_slot() doesn't check if the target root is NULL or
not, resulting the null-ptr-deref.

Add sanity check for btrfs root before using it in btrfs_search_slot().

References

• https://nvd.nist.gov/vuln/detail/CVE-2024-56774
• https://git.kernel.org/stable/c/3ed51857a50f530ac7a1482e069dfbd1298558d4
• https://git.kernel.org/stable/c/757171d1369b3b47f36932d40a05a0715496dcab
• https://git.kernel.org/stable/c/93992c3d9629b02dccf6849238559d5c24f2dece
• https://git.kernel.org/stable/c/c71d114ef68c95da5a82ec85a721ab31f5bd905b
• https://git.kernel.org/stable/c/db66fb87c21e8ae724886e6a464dcbac562a64c6