linux-kernel - [PATCH] cifs: fix underflow in parse_server

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Message-ID: <05c63e91-ce29-40aa-807c-ac730181c83e@moroto.mountain>
Date: Thu, 8 Feb 2024 13:18:46 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: Aurelien Aptel <aaptel@...e.com>
Cc: Steve French <sfrench@...ba.org>, Paulo Alcantara <pc@...guebit.com>,
	Ronnie Sahlberg <ronniesahlberg@...il.com>,
	Shyam Prasad N <sprasad@...rosoft.com>, Tom Talpey <tom@...pey.com>,
	linux-cifs@...r.kernel.org, samba-technical@...ts.samba.org,
	linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: [PATCH] cifs: fix underflow in parse_server_interfaces()

In this loop, we step through the buffer and after each item we check
if the size_left is greater than the minimum size we need.  However,
the problem is that "bytes_left" is type ssize_t while sizeof() is type
size_t.  That means that because of type promotion, the comparison is
done as an unsigned and if we have negative bytes left the loop
continues instead of ending.

Fixes: fe856be475f7 ("CIFS: parse and store info on iface queries")
Signed-off-by: Dan Carpenter <dan.carpenter@...aro.org>
---
 fs/smb/client/smb2ops.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/smb/client/smb2ops.c b/fs/smb/client/smb2ops.c
index b79b6bbd7103..bb3975dc9072 100644
--- a/fs/smb/client/smb2ops.c
+++ b/fs/smb/client/smb2ops.c
@@ -620,7 +620,7 @@ parse_server_interfaces(struct network_interface_info_ioctl_rsp *buf,
 		goto out;
 	}
 
-	while (bytes_left >= sizeof(*p)) {
+	while (bytes_left >= (ssize_t)sizeof(*p)) {
 		memset(&tmp_iface, 0, sizeof(tmp_iface));
 		tmp_iface.speed = le64_to_cpu(p->LinkSpeed);
 		tmp_iface.rdma_capable = le32_to_cpu(p->Capability & RDMA_CAPABLE) ? 1 : 0;
-- 
2.43.0