linux-kernel - [PATCH][next] cifsd: fix kfree of uninitialized pointer oid

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Message-Id: <20210610164603.554691-1-colin.king@canonical.com>
Date:   Thu, 10 Jun 2021 17:46:03 +0100
From:   Colin King <colin.king@...onical.com>
To:     Namjae Jeon <namjae.jeon@...sung.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Steve French <sfrench@...ba.org>,
        Hyunchul Lee <hyc.lee@...il.com>, linux-cifs@...r.kernel.org,
        linux-cifsd-devel@...ts.sourceforge.net
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH][next] cifsd: fix kfree of uninitialized pointer oid

From: Colin Ian King <colin.king@...onical.com>

Currently function ksmbd_neg_token_init_mech_type can kfree an
uninitialized pointer oid when the call to asn1_oid_decode fails
when vlen is out of range. All the other failure cases in
function asn1_oid_decode set *oid to NULL on an error, so fix the
issue by ensuring the vlen out of range error also nullifies the
pointer.

Fixes: 8bae4419ce63 ("cifsd: add goto fail in neg_token_init_mech_type()")
Addresses-Coverity: ("Uninitialized pointer read")
Signed-off-by: Colin Ian King <colin.king@...onical.com>
---
 fs/cifsd/asn1.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/cifsd/asn1.c b/fs/cifsd/asn1.c
index 2c63a3e5618b..b014f4638610 100644
--- a/fs/cifsd/asn1.c
+++ b/fs/cifsd/asn1.c
@@ -66,7 +66,7 @@ static bool asn1_oid_decode(const unsigned char *value, size_t vlen,
 
 	vlen += 1;
 	if (vlen < 2 || vlen > UINT_MAX / sizeof(unsigned long))
-		return false;
+		goto fail_nullify;
 
 	*oid = kmalloc(vlen * sizeof(unsigned long), GFP_KERNEL);
 	if (!*oid)
@@ -102,6 +102,7 @@ static bool asn1_oid_decode(const unsigned char *value, size_t vlen,
 
 fail:
 	kfree(*oid);
+fail_nullify:
 	*oid = NULL;
 	return false;
 }
-- 
2.31.1