[PATCH 5.4.y] cifs: fix integer overflow in match_server()

[Sasha Levin <sashal@kernel.org>]

From: Roman Smirnov <r.smirnov@omp.ru>

[ Upstream commit 2510859475d7f46ed7940db0853f3342bf1b65ee ]

The echo_interval is not limited in any way during mounting,
which makes it possible to write a large number to it. This can
cause an overflow when multiplying ctx->echo_interval by HZ in
match_server().

Add constraints for echo_interval to smb3_fs_context_parse_param().

Found by Linux Verification Center (linuxtesting.org) with Svace.

Fixes: adfeb3e00e8e1 ("cifs: Make echo interval tunable")
Cc: stable@vger.kernel.org
Signed-off-by: Roman Smirnov <r.smirnov@omp.ru>
Signed-off-by: Steve French <stfrench@microsoft.com>
[ Adapted to older CIFS filesystem structure and mount option parsing ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/cifs/connect.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index d8d9d90615440..93fc906f732bc 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -2144,6 +2144,11 @@ cifs_parse_mount_options(const char *mountdata, const char *devname,
 					 __func__);
 				goto cifs_parse_mount_err;
 			}
+			if (option < SMB_ECHO_INTERVAL_MIN ||
+			    option > SMB_ECHO_INTERVAL_MAX) {
+				cifs_dbg(VFS, "echo interval is out of bounds\n");
+				goto cifs_parse_mount_err;
+			}
 			vol->echo_interval = option;
 			break;
 		case Opt_snapshot:
-- 
2.51.0