staging: erofs: keep corrupted fs from crashing kernel in erofs_namei()

As Al pointed out, "
... and while we are at it, what happens to
	unsigned int nameoff = le16_to_cpu(de[mid].nameoff);
	unsigned int matched = min(startprfx, endprfx);

	struct qstr dname = QSTR_INIT(data + nameoff,
		unlikely(mid >= ndirents - 1) ?
			maxsize - nameoff :
			le16_to_cpu(de[mid + 1].nameoff) - nameoff);

	/* string comparison without already matched prefix */
	int ret = dirnamecmp(name, &dname, &matched);
if le16_to_cpu(de[...].nameoff) is not monotonically increasing?  I.e.
what's to prevent e.g. (unsigned)-1 ending up in dname.len?

Corrupted fs image shouldn't oops the kernel.. "

Revisit the related lookup flow to address the issue.

Fixes: d72d1ce60174 ("staging: erofs: add namei functions")
Cc: <[email protected]> # 4.19+
Suggested-by: Al Viro <[email protected]>
Signed-off-by: Gao Xiang <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

0 files changed, 0 insertions, 0 deletions