Bug 2378983 (CVE-2025-38257)

Summary: CVE-2025-38257 kernel: Linux kernel: Denial of Service via integer overflow in s390/pkey memory allocation
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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OS: Linux   
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A flaw was found in the Linux kernel's s390/pkey component. A local user could exploit an integer overflow vulnerability in the `memdup_user()` size calculation when handling `apqn` target list entries. This overflow can cause the allocated memory size to be out of sync with the described size, leading to unpredictable system behavior and potentially a denial of service (DoS).
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Description OSIDB Bzimport 2025-07-09 11:01:44 UTC 
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).
Comment 1 Jon Moroney 2025-07-09 17:50:38 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2025070935-CVE-2025-38257-3e5d@gregkh/T