cifs: Fix integer overflow while processing actimeo mount option

Murad Masimov · Steve French · commit 64f690ee22c9 · 2025-03-13T08:41:28.000-05:00
User-provided mount parameter actimeo 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: 6d20e84 ("cifs: add attribute cache timeout (actimeo) tunable") Signed-off-by: Murad Masimov <m.masimov@mt-integration.ru> Signed-off-by: Steve French <stfrench@microsoft.com>
diff --git a/fs/smb/client/fs_context.c b/fs/smb/client/fs_context.c
@@ -1358,7 +1358,7 @@ static int smb3_fs_context_parse_param(struct fs_context *fc,
 		ctx->acdirmax = HZ * result.uint_32;
 		break;
 	case Opt_actimeo:
-		if (HZ * result.uint_32 > CIFS_MAX_ACTIMEO) {
+		if (result.uint_32 > CIFS_MAX_ACTIMEO / HZ) {
 			cifs_errorf(fc, "timeout too large\n");
 			goto cifs_parse_mount_err;
 		}

Original file line number	Diff line number	Diff line change
`@@ -1358,7 +1358,7 @@ static int smb3_fs_context_parse_param(struct fs_context *fc,`
`1358`	`1358`	`ctx->acdirmax = HZ * result.uint_32;`
`1359`	`1359`	`break;`
`1360`	`1360`	`case Opt_actimeo:`
`1361`		`- if (HZ * result.uint_32 > CIFS_MAX_ACTIMEO) {`
	`1361`	`+ if (result.uint_32 > CIFS_MAX_ACTIMEO / HZ) {`
`1362`	`1362`	`cifs_errorf(fc, "timeout too large\n");`
`1363`	`1363`	`goto cifs_parse_mount_err;`
`1364`	`1364`	`}`