patch "staging: erofs: avoid endless loop of invalid lookback distance 0" added to staging-next

This is a note to let you know that I've just added the patch titled

staging: erofs: avoid endless loop of invalid lookback distance 0

to my staging git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging.git
in the staging-next branch.

The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)

The patch will also be merged in the next major kernel release during the merge window.

If you have any questions about this process, please let me know.

From 598bb8913d015150b7734b55443c0e53e7189fc7 Mon Sep 17 00:00:00 2001
From: Gao Xiang <[email protected]>
Date: Mon, 19 Aug 2019 18:34:26 +0800
Subject: staging: erofs: avoid endless loop of invalid lookback distance 0

As reported by erofs-utils fuzzer, Lookback distance should be a positive number, so it should be actually looked back rather than spinning.

---
 drivers/staging/erofs/zmap.c | 6 ++++++
 1 file changed, 6 insertions(+)

index 7408e86823a4..774dacbc5b32 100644
@@ -350,6 +350,12 @@ static int vle_extent_lookback(struct z_erofs_maprecorder *m,
 
 	switch (m->type) {
 	case Z_EROFS_VLE_CLUSTER_TYPE_NONHEAD:
+		if (unlikely(!m->delta[0])) {
+			errln("invalid lookback distance 0 at nid %llu",
+			      vi->nid);
+			DBG_BUGON(1);
+			return -EFSCORRUPTED;
+		}
 		return vle_extent_lookback(m, m->delta[0]);
 	case Z_EROFS_VLE_CLUSTER_TYPE_PLAIN:
 		map->m_flags &= ~EROFS_MAP_ZIPPED;

2.23.0