cifs: Fix integer overflow while processing actimeo mount option

cifs: Fix integer overflow while processing actimeo mount option

[ Upstream commit 64f690ee22c99e16084e0e45181b2a1eed2fa149 ]

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: 6d20e8406f09 ("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>
Signed-off-by: Sasha Levin <sashal@kernel.org>