linux-kernel - [PATCH AUTOSEL 4.14 6/9] smb3: check xattr value length earlier

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Message-Id: <20220814162959.2399011-6-sashal@kernel.org>
Date:   Sun, 14 Aug 2022 12:29:56 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Steve French <stfrench@...rosoft.com>,
        Ronnie Sahlberg <lsahlber@...hat.com>,
        Sasha Levin <sashal@...nel.org>, sfrench@...ba.org,
        linux-cifs@...r.kernel.org, samba-technical@...ts.samba.org
Subject: [PATCH AUTOSEL 4.14 6/9] smb3: check xattr value length earlier

From: Steve French <stfrench@...rosoft.com>

[ Upstream commit 5fa2cffba0b82336a2244d941322eb1627ff787b ]

Coverity complains about assigning a pointer based on
value length before checking that value length goes
beyond the end of the SMB.  Although this is even more
unlikely as value length is a single byte, and the
pointer is not dereferenced until laterm, it is clearer
to check the lengths first.

Addresses-Coverity: 1467704 ("Speculative execution data leak")
Reviewed-by: Ronnie Sahlberg <lsahlber@...hat.com>
Signed-off-by: Steve French <stfrench@...rosoft.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 fs/cifs/smb2ops.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
index 3280a801b1d7..069eb2533e7f 100644
--- a/fs/cifs/smb2ops.c
+++ b/fs/cifs/smb2ops.c
@@ -463,9 +463,7 @@ move_smb2_ea_to_cifs(char *dst, size_t dst_size,
 	size_t name_len, value_len, user_name_len;
 
 	while (src_size > 0) {
-		name = &src->ea_data[0];
 		name_len = (size_t)src->ea_name_length;
-		value = &src->ea_data[src->ea_name_length + 1];
 		value_len = (size_t)le16_to_cpu(src->ea_value_length);
 
 		if (name_len == 0) {
@@ -478,6 +476,9 @@ move_smb2_ea_to_cifs(char *dst, size_t dst_size,
 			goto out;
 		}
 
+		name = &src->ea_data[0];
+		value = &src->ea_data[src->ea_name_length + 1];
+
 		if (ea_name) {
 			if (ea_name_len == name_len &&
 			    memcmp(ea_name, name, name_len) == 0) {
-- 
2.35.1