s390/pkey: Prevent overflow in size calculation for memdup_user()

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: s390/pkey: Prevent overflow in size calculation for memdup_user() Number of apqn target list entries contained in 'nr_apqns' variable is determined by userspace via an ioctl call so the result of the product in calculation of size passed to memdup_user() may overflow. In this case the actual size of the allocated area and the value describing it won't be in sync leading to various types of unpredictable behaviour later. Use a proper memdup_array_user() helper which returns an error if an overflow is detected. Note that it is different from when nr_apqns is initially zero - that case is considered valid and should be handled in subsequent pkey_handler implementations. Found by Linux Verification Center (linuxtesting.org).

References

• https://git.kernel.org/stable/c/ad1bdd24a02d5a8d119af8e4cd50933780a6d29f
• https://git.kernel.org/stable/c/faa1ab4a23c42e34dc000ef4977b751d94d5148c
• https://git.kernel.org/stable/c/88f3869649edbc4a13f6c2877091f81cd5a50f05
• https://git.kernel.org/stable/c/f855b119e62b004a5044ed565f2a2b368c4d3f16
• https://git.kernel.org/stable/c/73483ca7e07a5e39bdf612eec9d3d293e8bef649
• https://git.kernel.org/stable/c/7360ee47599af91a1d5f4e74d635d9408a54e489