The patch below does not apply to the 4.19-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 598bb8913d015150b7734b55443c0e53e7189fc7 Mon Sep 17 00:00:00 2001

From: Gao Xiang gaoxiang25@huawei.com Date: Mon, 19 Aug 2019 18:34:26 +0800 Subject: [PATCH] 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.

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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org

diff --git a/drivers/staging/erofs/zmap.c b/drivers/staging/erofs/zmap.c index 7408e86823a4..774dacbc5b32 100644 --- a/drivers/staging/erofs/zmap.c +++ b/drivers/staging/erofs/zmap.c @@ -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;