cifs: Fix integer overflow while processing acregmax mount option

[ Upstream commit 7489161b1852390b4413d57f2457cd40b34da6cc ]

User-provided mount parameter acregmax 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: 5780464614f6 ("cifs: Add new parameter "acregmax" for distinct file and directory metadata timeout")
Signed-off-by: Murad Masimov <m.masimov@mt-integration.ru>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/fs/cifs/fs_context.c b/fs/cifs/fs_context.c
index fb3651513f83aad23f1fd9f821b37578a61625af..d86cbed997fdd61e108bad051ad9b3c82667033c 100644 (file)
--- a/fs/cifs/fs_context.c
+++ b/fs/cifs/fs_context.c
@@ -1055,11 +1055,11 @@ static int smb3_fs_context_parse_param(struct fs_context *fc,
                ctx->got_wsize = true;
                break;
        case Opt_acregmax:
-               ctx->acregmax = HZ * result.uint_32;
-               if (ctx->acregmax > CIFS_MAX_ACTIMEO) {
+               if (result.uint_32 > CIFS_MAX_ACTIMEO / HZ) {
                        cifs_errorf(fc, "acregmax too large\n");
                        goto cifs_parse_mount_err;
                }
+               ctx->acregmax = HZ * result.uint_32;
                break;
        case Opt_acdirmax:
                ctx->acdirmax = HZ * result.uint_32;