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erofs: avoid infinite loops due to corrupted subpage compact indexes

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Robert reported an infinite loop observed by two crafted images.

The root cause is that `clusterofs` can be larger than `lclustersize`
for !NONHEAD `lclusters` in corrupted subpage compact indexes, e.g.:

  blocksize = lclustersize = 512   lcn = 6   clusterofs = 515

Move the corresponding check for full compress indexes to
`z_erofs_load_lcluster_from_disk()` to also cover subpage compact
compress indexes.

It also fixes the position of `m->type >= Z_EROFS_LCLUSTER_TYPE_MAX`
check, since it should be placed right after
`z_erofs_load_{compact,full}_lcluster()`.

Fixes: 8d2517aaee ("erofs: fix up compacted indexes for block size < 4096")
Fixes: 1a5223c182 ("erofs: do sanity check on m->type in z_erofs_load_compact_lcluster()")
Reported-by: Robert Morris <rtm@csail.mit.edu>
Closes: https://lore.kernel.org/r/35167.1760645886@localhost
Reviewed-by: Hongbo Li <lihongbo22@huawei.com>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
This commit is contained in:
Gao Xiang
2025-10-17 15:05:38 +08:00
parent a429b76114
commit e13d315ae0
1 changed files with 18 additions and 14 deletions
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32
fs/erofs/zmap.c
View File

@@ -55,10 +55,6 @@ static int z_erofs_load_full_lcluster(struct z_erofs_maprecorder *m,
} else {
m->partialref = !!(advise & Z_EROFS_LI_PARTIAL_REF);
m->clusterofs = le16_to_cpu(di->di_clusterofs);
if (m->clusterofs >= 1 << vi->z_lclusterbits) {
DBG_BUGON(1);
return -EFSCORRUPTED;
}
m->pblk = le32_to_cpu(di->di_u.blkaddr);
}
return 0;
@@ -240,21 +236,29 @@ static int z_erofs_load_compact_lcluster(struct z_erofs_maprecorder *m,
static int z_erofs_load_lcluster_from_disk(struct z_erofs_maprecorder *m,
unsigned int lcn, bool lookahead)
{
struct erofs_inode *vi = EROFS_I(m->inode);
int err;
if (vi->datalayout == EROFS_INODE_COMPRESSED_COMPACT) {
err = z_erofs_load_compact_lcluster(m, lcn, lookahead);
} else {
DBG_BUGON(vi->datalayout != EROFS_INODE_COMPRESSED_FULL);
err = z_erofs_load_full_lcluster(m, lcn);
}
if (err)
return err;
if (m->type >= Z_EROFS_LCLUSTER_TYPE_MAX) {
erofs_err(m->inode->i_sb, "unknown type %u @ lcn %u of nid %llu",
m->type, lcn, EROFS_I(m->inode)->nid);
m->type, lcn, EROFS_I(m->inode)->nid);
DBG_BUGON(1);
return -EOPNOTSUPP;
} else if (m->type != Z_EROFS_LCLUSTER_TYPE_NONHEAD &&
m->clusterofs >= (1 << vi->z_lclusterbits)) {
DBG_BUGON(1);
return -EFSCORRUPTED;
}
switch (EROFS_I(m->inode)->datalayout) {
case EROFS_INODE_COMPRESSED_FULL:
return z_erofs_load_full_lcluster(m, lcn);
case EROFS_INODE_COMPRESSED_COMPACT:
return z_erofs_load_compact_lcluster(m, lcn, lookahead);
default:
return -EINVAL;
}
return 0;
}
static int z_erofs_extent_lookback(struct z_erofs_maprecorder *m,