diff options
| author | Gao Xiang <hsiangkao@linux.alibaba.com> | 2025-10-12 21:59:25 +0800 |
|---|---|---|
| committer | Gao Xiang <hsiangkao@linux.alibaba.com> | 2025-10-17 15:21:36 +0800 |
| commit | a429b76114aaca3ef1aff4cd469dcf025431bd11 (patch) | |
| tree | 9d6ea924b690a5deb17553392546323412f14953 | |
| parent | 3a8660878839faadb4f1a6dd72c3179c1df56787 (diff) | |
erofs: fix crafted invalid cases for encoded extents
Robert recently reported two corrupted images that can cause system
crashes, which are related to the new encoded extents introduced
in Linux 6.15:
- The first one [1] has plen != 0 (e.g. plen == 0x2000000) but
(plen & Z_EROFS_EXTENT_PLEN_MASK) == 0. It is used to represent
special extents such as sparse extents (!EROFS_MAP_MAPPED), but
previously only plen == 0 was handled;
- The second one [2] has pa 0xffffffffffdcffed and plen 0xb4000,
then "cur [0xfffffffffffff000] += bvec.bv_len [0x1000]" in
"} while ((cur += bvec.bv_len) < end);" wraps around, causing an
out-of-bound access of pcl->compressed_bvecs[] in
z_erofs_submit_queue(). EROFS only supports 48-bit physical block
addresses (up to 1EiB for 4k blocks), so add a sanity check to
enforce this.
Fixes: 1d191b4ca51d ("erofs: implement encoded extent metadata")
Reported-by: Robert Morris <rtm@csail.mit.edu>
Closes: https://lore.kernel.org/r/75022.1759355830@localhost [1]
Closes: https://lore.kernel.org/r/80524.1760131149@localhost [2]
Reviewed-by: Hongbo Li <lihongbo22@huawei.com>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
| -rw-r--r-- | fs/erofs/zmap.c | 7 |
1 files changed, 6 insertions, 1 deletions
diff --git a/fs/erofs/zmap.c b/fs/erofs/zmap.c index e5581dbeb4c2..8007814f721e 100644 --- a/fs/erofs/zmap.c +++ b/fs/erofs/zmap.c @@ -596,7 +596,7 @@ static int z_erofs_map_blocks_ext(struct inode *inode, vi->z_fragmentoff = map->m_plen; if (recsz > offsetof(struct z_erofs_extent, pstart_lo)) vi->z_fragmentoff |= map->m_pa << 32; - } else if (map->m_plen) { + } else if (map->m_plen & Z_EROFS_EXTENT_PLEN_MASK) { map->m_flags |= EROFS_MAP_MAPPED | EROFS_MAP_FULL_MAPPED | EROFS_MAP_ENCODED; fmt = map->m_plen >> Z_EROFS_EXTENT_PLEN_FMT_BIT; @@ -715,6 +715,7 @@ static int z_erofs_map_sanity_check(struct inode *inode, struct erofs_map_blocks *map) { struct erofs_sb_info *sbi = EROFS_I_SB(inode); + u64 pend; if (!(map->m_flags & EROFS_MAP_ENCODED)) return 0; @@ -732,6 +733,10 @@ static int z_erofs_map_sanity_check(struct inode *inode, if (unlikely(map->m_plen > Z_EROFS_PCLUSTER_MAX_SIZE || map->m_llen > Z_EROFS_PCLUSTER_MAX_DSIZE)) return -EOPNOTSUPP; + /* Filesystems beyond 48-bit physical block addresses are invalid */ + if (unlikely(check_add_overflow(map->m_pa, map->m_plen, &pend) || + (pend >> sbi->blkszbits) >= BIT_ULL(48))) + return -EFSCORRUPTED; return 0; } |