[lvc-project] [PATCH 2/4] cifs: Fix integer overflow while processing acdirmax mount option

[Murad Masimov]

User-provided mount parameter acdirmax of type u32 is intended to have
an upper limit, but before it is validated, the value is converted from
seconds to jiffies which can lead to an integer overflow.

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

Fixes: 4c9f948142a5 ("cifs: Add new mount parameter "acdirmax" to allow caching directory metadata")
Signed-off-by: Murad Masimov <m.masimov at mt-integration.ru>
---
 fs/smb/client/fs_context.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/smb/client/fs_context.c b/fs/smb/client/fs_context.c
index e9045fcf843e..7749309de782 100644
--- a/fs/smb/client/fs_context.c
+++ b/fs/smb/client/fs_context.c
@@ -1347,11 +1347,11 @@ static int smb3_fs_context_parse_param(struct fs_context *fc,
 		ctx->acregmax = HZ * result.uint_32;
 		break;
 	case Opt_acdirmax:
-		ctx->acdirmax = HZ * result.uint_32;
-		if (ctx->acdirmax > CIFS_MAX_ACTIMEO) {
+		if (result.uint_32 > CIFS_MAX_ACTIMEO / HZ) {
 			cifs_errorf(fc, "acdirmax too large\n");
 			goto cifs_parse_mount_err;
 		}
+		ctx->acdirmax = HZ * result.uint_32;
 		break;
 	case Opt_actimeo:
 		if (HZ * result.uint_32 > CIFS_MAX_ACTIMEO) {
--
2.39.2