linux-kernel - [PATCH] fs: jffs2: Fix possible null-pointer dereferences in jffs2_add_frag_to

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Date:   Wed, 24 Jul 2019 10:46:58 +0800
From:   Jia-Ju Bai <baijiaju1990@...il.com>
To:     dwmw2@...radead.org, richard@....at
Cc:     linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Jia-Ju Bai <baijiaju1990@...il.com>
Subject: [PATCH] fs: jffs2: Fix possible null-pointer dereferences in jffs2_add_frag_to_fragtree()

In jffs2_add_frag_to_fragtree(), there is an if statement on line 223 to
check whether "this" is NULL:
    if (this)

When "this" is NULL, it is used at several places, such as on line 249:
    if (this->node)
and on line 260:
    if (newfrag->ofs > this->ofs)

Thus possible null-pointer dereferences may occur.

To fix these bugs, -EINVAL is returned when "this" is NULL.

These bugs are found by a static analysis tool STCheck written by us.

Signed-off-by: Jia-Ju Bai <baijiaju1990@...il.com>
---
 fs/jffs2/nodelist.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/jffs2/nodelist.c b/fs/jffs2/nodelist.c
index b86c78d178c6..021a4a2190ee 100644
--- a/fs/jffs2/nodelist.c
+++ b/fs/jffs2/nodelist.c
@@ -226,7 +226,7 @@ static int jffs2_add_frag_to_fragtree(struct jffs2_sb_info *c, struct rb_root *r
 		lastend = this->ofs + this->size;
 	} else {
 		dbg_fragtree2("lookup gave no frag\n");
-		lastend = 0;
+		return -EINVAL;
 	}
 
 	/* See if we ran off the end of the fragtree */
-- 
2.17.0