linux-kernel - [PATCH] tools: lib: subcmd: Fix null pointer dereference

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Date:   Sat, 29 Sep 2018 22:33:25 +0530
From:   Tapasweni Pathak <tapaswenipathak@...il.com>
To:     gregkh@...uxfoundation.org, kstewart@...uxfoundation.org,
        pombredanne@...b.com, tglx@...utronix.de,
        tapaswenipathak@...il.com, linux-kernel@...r.kernel.org
Cc:     tapaswenipathak@...il.com
Subject: [PATCH] tools: lib: subcmd: Fix null pointer dereference

Add null check before dereferencing ent. ent is pointer to memory
allocated using malloc and is dereferenced immediately without
null check.

Found using Facebook's Infer. Build tested it.

Signed-off-by: Tapasweni Pathak <tapaswenipathak@...il.com>
---
Another option is to dereference only inside if (ent).
 tools/lib/subcmd/help.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/tools/lib/subcmd/help.c b/tools/lib/subcmd/help.c
index 2859f10..b805d1d 100644
--- a/tools/lib/subcmd/help.c
+++ b/tools/lib/subcmd/help.c
@@ -16,13 +16,18 @@
 void add_cmdname(struct cmdnames *cmds, const char *name, size_t len)
 {
 	struct cmdname *ent = malloc(sizeof(*ent) + len + 1);
-
+        if (!ent) {
+                printf("mem alloc failed\n");
+                goto error;
+        }
 	ent->len = len;
 	memcpy(ent->name, name, len);
 	ent->name[len] = 0;

 	ALLOC_GROW(cmds->names, cmds->cnt + 1, cmds->alloc);
 	cmds->names[cmds->cnt++] = ent;
+        error:
+                if (ent) free(ent);
 }

 void clean_cmdnames(struct cmdnames *cmds)
--
2.7.4