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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>
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
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
fs/erofs/decompressor.c
View File

@ -398,7 +398,7 @@ int z_erofs_parse_cfgs(struct super_block *sb, struct erofs_super_block *dsb)
int size, ret = 0;
if (!erofs_sb_has_compr_cfgs(sbi)) {
sbi->available_compr_algs = Z_EROFS_COMPRESSION_LZ4;
sbi->available_compr_algs = 1 << Z_EROFS_COMPRESSION_LZ4;
return z_erofs_load_lz4_config(sb, dsb, NULL, 0);
}

23
fs/erofs/zmap.c
View File

@ -458,7 +458,7 @@ static int z_erofs_do_map_blocks(struct inode *inode,
.map = map,
};
int err = 0;
unsigned int lclusterbits, endoff;
unsigned int lclusterbits, endoff, afmt;
unsigned long initial_lcn;
unsigned long long ofs, end;
@ -547,17 +547,20 @@ static int z_erofs_do_map_blocks(struct inode *inode,
err = -EFSCORRUPTED;
goto unmap_out;
}
if (vi->z_advise & Z_EROFS_ADVISE_INTERLACED_PCLUSTER)
map->m_algorithmformat =
Z_EROFS_COMPRESSION_INTERLACED;
else
map->m_algorithmformat =
Z_EROFS_COMPRESSION_SHIFTED;
} else if (m.headtype == Z_EROFS_LCLUSTER_TYPE_HEAD2) {
map->m_algorithmformat = vi->z_algorithmtype[1];
afmt = vi->z_advise & Z_EROFS_ADVISE_INTERLACED_PCLUSTER ?
Z_EROFS_COMPRESSION_INTERLACED :
Z_EROFS_COMPRESSION_SHIFTED;
} else {
map->m_algorithmformat = vi->z_algorithmtype[0];
afmt = m.headtype == Z_EROFS_LCLUSTER_TYPE_HEAD2 ?
vi->z_algorithmtype[1] : vi->z_algorithmtype[0];
if (!(EROFS_I_SB(inode)->available_compr_algs & (1 << afmt))) {
erofs_err(inode->i_sb, "inconsistent algorithmtype %u for nid %llu",
afmt, vi->nid);
err = -EFSCORRUPTED;
goto unmap_out;
}
}
map->m_algorithmformat = afmt;
if ((flags & EROFS_GET_BLOCKS_FIEMAP) ||
((flags & EROFS_GET_BLOCKS_READMORE) &&