Affected: Linux

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

erofs: fix inconsistent per-file compression format

EROFS can select compression algorithms on a per-file basis, and each per-file compression algorithm needs to be marked in the on-disk superblock for initialization.

However, syzkaller can generate inconsistent crafted images that use an unsupported algorithmtype for specific inodes, e.g. use MicroLZMA algorithmtype even it's not set in `sbi->available_compr_algs`. This can lead to an unexpected "BUG: kernel NULL pointer dereference" if the corresponding decompressor isn't built-in.

Fix this by checking against `sbi->available_compr_algs` for each m_algorithmformat request. Incorrect !erofs_sb_has_compr_cfgs preset bitmap is now fixed together since it was harmless previously.