rjmcmahon
/
umber-kernel
1
0
Fork 0
Code Issues 1 Pull Requests Packages Projects Releases Wiki Activity

erofs: fix interlaced plain identification for encoded extents 

[ Upstream commit 4a2d046e4b13202a6301a993961f5b30ae4d7119 ]

Only plain data whose start position and on-disk physical length are
both aligned to the block size should be classified as interlaced
plain extents. Otherwise, it must be treated as shifted plain extents.

This issue was found by syzbot using a crafted compressed image
containing plain extents with unaligned physical lengths, which can
cause OOB read in z_erofs_transform_plain().

Reported-and-tested-by: syzbot+d988dc155e740d76a331@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/r/699d5714.050a0220.cdd3c.03e7.GAE@google.com
Fixes: 1d191b4ca5 ("erofs: implement encoded extent metadata")
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Gao Xiang 2026-02-24 18:31:25 +08:00 committed by Sasha Levin
parent d2e7c898cc
commit 9d5a97bc71
1 changed files with 5 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

9
fs/erofs/zmap.c
View File

@ -513,6 +513,7 @@ static int z_erofs_map_blocks_ext(struct inode *inode,
unsigned int recsz = z_erofs_extent_recsize(vi->z_advise);
erofs_off_t pos = round_up(Z_EROFS_MAP_HEADER_END(erofs_iloc(inode) +
vi->inode_isize + vi->xattr_isize), recsz);
unsigned int bmask = sb->s_blocksize - 1;
bool in_mbox = erofs_inode_in_metabox(inode);
erofs_off_t lend = inode->i_size;
erofs_off_t l, r, mid, pa, la, lstart;
@ -596,17 +597,17 @@ static int z_erofs_map_blocks_ext(struct inode *inode,
map->m_flags |= EROFS_MAP_MAPPED |
EROFS_MAP_FULL_MAPPED | EROFS_MAP_ENCODED;
fmt = map->m_plen >> Z_EROFS_EXTENT_PLEN_FMT_BIT;
if (map->m_plen & Z_EROFS_EXTENT_PLEN_PARTIAL)
map->m_flags |= EROFS_MAP_PARTIAL_REF;
map->m_plen &= Z_EROFS_EXTENT_PLEN_MASK;
if (fmt)
map->m_algorithmformat = fmt - 1;
else if (interlaced && !erofs_blkoff(sb, map->m_pa))
else if (interlaced && !((map->m_pa | map->m_plen) & bmask))
map->m_algorithmformat =
Z_EROFS_COMPRESSION_INTERLACED;
else
map->m_algorithmformat =
Z_EROFS_COMPRESSION_SHIFTED;
if (map->m_plen & Z_EROFS_EXTENT_PLEN_PARTIAL)
map->m_flags |= EROFS_MAP_PARTIAL_REF;
map->m_plen &= Z_EROFS_EXTENT_PLEN_MASK;
}
}
map->m_llen = lend - map->m_la;