From: Gao Xiang <[email protected]> [ Upstream commit 118a8cf504d7dfa519562d000f423ee3ca75d2c4 ]
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: <[email protected]> Fixes: 8f89926290c4 ("erofs: get compression algorithms directly on mapping") Fixes: 622ceaddb764 ("erofs: lzma compression support") Reviewed-by: Yue Hu <[email protected]> Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Gao Xiang <[email protected]> Signed-off-by: Yue Hu <[email protected]> --- fs/erofs/decompressor.c | 2 +- fs/erofs/zmap.c | 23 +++++++++++++---------- 2 files changed, 14 insertions(+), 11 deletions(-) diff --git a/fs/erofs/decompressor.c b/fs/erofs/decompressor.c index ae3cfd018d99..1eefa4411e06 100644 --- a/fs/erofs/decompressor.c +++ b/fs/erofs/decompressor.c @@ -396,7 +396,7 @@ 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); } diff --git a/fs/erofs/zmap.c b/fs/erofs/zmap.c index 0337b70b2dac..abcded1acd19 100644 --- a/fs/erofs/zmap.c +++ b/fs/erofs/zmap.c @@ -610,7 +610,7 @@ 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; @@ -700,17 +700,20 @@ 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_VLE_CLUSTER_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_VLE_CLUSTER_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) && -- 2.17.1
