CVE-2024-57877 Information

Jan 12, 2025 cve

Description

In the Linux kernel the following vulnerability has been resolved:

arm64: ptrace: fix partial SETREGSET for NT_ARM_POE

Currently poe_set() doesn’t initialize the temporary ‘ctrl’ variable and a SETREGSET call with a length of zero will leave this uninitialized. Consequently an arbitrary value will be written back to target->thread.por_el0 potentially leaking up to 64 bits of memory from the kernel stack. The read is limited to a specific slot on the stack and the issue does not provide a write mechanism.

Fix this by initializing the temporary value before copying the regset from userspace as for other regsets (e.g. NT_PRSTATUS NT_PRFPREG NT_ARM_SYSTEM_CALL). In the case of a zero-length write the existing contents of POR_EL1 will be retained.

Before this patch:

| ./poe-test | Attempting to write NT_ARM_POE::por_el0 = 0x900d900d900d900d | SETREGSET(nt=0x40f len=8) wrote 8 bytes | | Attempting to read NT_ARM_POE::por_el0 | GETREGSET(nt=0x40f len=8) read 8 bytes | Read NT_ARM_POE::por_el0 = 0x900d900d900d900d | | Attempting to write NT_ARM_POE (zero length) | SETREGSET(nt=0x40f len=0) wrote 0 bytes | | Attempting to read NT_ARM_POE::por_el0 | GETREGSET(nt=0x40f len=8) read 8 bytes | Read NT_ARM_POE::por_el0 = 0xffff8000839c3d50

After this patch:

| ./poe-test | Attempting to write NT_ARM_POE::por_el0 = 0x900d900d900d900d | SETREGSET(nt=0x40f len=8) wrote 8 bytes | | Attempting to read NT_ARM_POE::por_el0 | GETREGSET(nt=0x40f len=8) read 8 bytes | Read NT_ARM_POE::por_el0 = 0x900d900d900d900d | | Attempting to write NT_ARM_POE (zero length) | SETREGSET(nt=0x40f len=0) wrote 0 bytes | | Attempting to read NT_ARM_POE::por_el0 | GETREGSET(nt=0x40f len=8) read 8 bytes | Read NT_ARM_POE::por_el0 = 0x900d900d900d900d

Reference

https://git.kernel.org/stable/c/4105dd76bc8ad6529d47157ef0565cb84ca6676c https://git.kernel.org/stable/c/594bfc4947c4fcabba1318d8384c61a29a6b89fb

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