CVE-2022-49348

Summary

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

ext4: filter out EXT4_FC_REPLAY from on-disk superblock field s_state

The EXT4_FC_REPLAY bit in sbi->s_mount_state is used to indicate that we are in the middle of replay the fast commit journal. This was actually a mistake, since the sbi->s_mount_info is initialized from es->s_state. Arguably s_mount_state is misleadingly named, but the name is historical — s_mount_state and s_state dates back to ext2.

What should have been used is the ext4_{set,clear,test}mount_flag() inline functions, which sets EXT4_MF* bits in sbi->s_mount_flags.

The problem with using EXT4_FC_REPLAY is that a maliciously corrupted superblock could result in EXT4_FC_REPLAY getting set in s_mount_state. This bypasses some sanity checks, and this can trigger a BUG() in ext4_es_cache_extent(). As a easy-to-backport-fix, filter out the EXT4_FC_REPLAY bit for now. We should eventually transition away from EXT4_FC_REPLAY to something like EXT4_MF_REPLAY.

Affected Software

VendorProductVersion RangeStatus
LinuxLinux8016e29f4362e285f0f7e38fadc61a5b7bdfdfa2 < cc5b09cb6dacd4b32640537929ab4ee8fb2b9e04affected
LinuxLinux8016e29f4362e285f0f7e38fadc61a5b7bdfdfa2 < b99fd73418350dea360da8311e87a6a7b0e15a4caffected
LinuxLinux8016e29f4362e285f0f7e38fadc61a5b7bdfdfa2 < af2f1932743fb52ebcb008ad7ac500d9df0aa796affected
LinuxLinux8016e29f4362e285f0f7e38fadc61a5b7bdfdfa2 < 55b4dbb29054a05d839562f6d635ce05669b016daffected
LinuxLinux8016e29f4362e285f0f7e38fadc61a5b7bdfdfa2 < c878bea3c9d724ddfa05a813f30de3d25a0ba83faffected
LinuxLinux5.10affected
LinuxLinux0 < 5.10unaffected
LinuxLinux5.10.121 <= 5.10.*unaffected
LinuxLinux5.15.46 <= 5.15.*unaffected
LinuxLinux5.17.14 <= 5.17.*unaffected
LinuxLinux5.18.3 <= 5.18.*unaffected
LinuxLinux5.19 <= *unaffected

Weaknesses

References