CVE-2024-26603

A flaw was found in the Linux kernel's x86/fpu module, which revolves around an issue with relying on user space for critical information regarding the xsave buffer. In the affected scenario, the expected size of the user space buffer is derived from user-controlled data, specifically, fx_sw->xstate_size. By manipulating this value, an attacker could construct a malicious sigreturn frame where the indicated size is smaller than required by valid bits in fx_sw->xfeatures. Furthermore, the attacker could unmap portions of the fpu buffer in the user space, rendering them inaccessible to xrstor.

This manipulation leads to a situation where xrstor repeatedly attempts to restore and access an unmapped area, causing a fault. However, the fault_in_readable function erroneously succeeds because the accessed region, buf + fx_sw->xstate_size, remains within the mapped area. Consequently, the system enters a perpetual loop as xrstor continually retries the operation.

This vulnerability, while technically significant due to its potential for exploitation, is classified as Low severity for several reasons. First, successful exploitation requires a precise set of conditions, including the ability to manipulate the fx_sw->xstate_size parameter, which may not always be feasible. Additionally, the exploit's impact is limited to a specific subsystem (x86/fpu) within the Linux kernel, thereby reducing its overall scope and potential for widespread harm. Moreover, the loop resulting from the fault condition does not result in a system compromise or escalation of privileges but rather leads to a denial-of-service situation, which can be mitigated through a system reboot or other administrative actions.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

Mitigation for this issue is either not available or the currently available options don't meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.