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Subject[PATCH 5.3 146/148] staging: erofs: avoid endless loop of invalid lookback distance 0
Date
From: Gao Xiang <gaoxiang25@huawei.com>

commit 598bb8913d015150b7734b55443c0e53e7189fc7 upstream.

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

Fixes: 02827e1796b3 ("staging: erofs: add erofs_map_blocks_iter")
Cc: <stable@vger.kernel.org> # 4.19+
Signed-off-by: Gao Xiang <gaoxiang25@huawei.com>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Link: https://lore.kernel.org/r/20190819103426.87579-7-gaoxiang25@huawei.com
[ Gao Xiang: Since earlier kernels don't define EFSCORRUPTED,
let's use EIO instead. ]
Signed-off-by: Gao Xiang <gaoxiang25@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/staging/erofs/zmap.c | 6 ++++++
1 file changed, 6 insertions(+)

--- a/drivers/staging/erofs/zmap.c
+++ b/drivers/staging/erofs/zmap.c
@@ -350,6 +350,12 @@ static int vle_extent_lookback(struct z_

switch (m->type) {
case Z_EROFS_VLE_CLUSTER_TYPE_NONHEAD:
+ if (!m->delta[0]) {
+ errln("invalid lookback distance 0 at nid %llu",
+ vi->nid);
+ DBG_BUGON(1);
+ return -EIO;
+ }
return vle_extent_lookback(m, m->delta[0]);
case Z_EROFS_VLE_CLUSTER_TYPE_PLAIN:
map->m_flags &= ~EROFS_MAP_ZIPPED;

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