erofs: fix inconsistent per-file compression format

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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.

Reported-by: <bugreport@ubisectech.com>
Fixes: 8f89926290 ("erofs: get compression algorithms directly on mapping")
Fixes: 622ceaddb7 ("erofs: lzma compression support")
Reviewed-by: Yue Hu <huyue2@coolpad.com>
Link: https://lore.kernel.org/r/20240113150602.1471050-1-hsiangkao@linux.alibaba.com
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>

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This commit is contained in:

Gao Xiang 2024-01-13 23:06:02 +08:00

parent 0dd3ee3112

commit 118a8cf504

2 changed files with 14 additions and 11 deletions

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2

fs/erofs/decompressor.c

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23

fs/erofs/zmap.c

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