CVE-2024-57878 Information

Jan 12, 2025 cve

Description

In the Linux kernel the following vulnerability has been resolved:

arm64: ptrace: fix partial SETREGSET for NT_ARM_FPMR

Currently fpmr_set() doesn’t initialize the temporary ‘fpmr’ 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.uw.fpmr 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 FPMR will be retained.

Before this patch:

| ./fpmr-test | Attempting to write NT_ARM_FPMR::fpmr = 0x900d900d900d900d | SETREGSET(nt=0x40e len=8) wrote 8 bytes | | Attempting to read NT_ARM_FPMR::fpmr | GETREGSET(nt=0x40e len=8) read 8 bytes | Read NT_ARM_FPMR::fpmr = 0x900d900d900d900d | | Attempting to write NT_ARM_FPMR (zero length) | SETREGSET(nt=0x40e len=0) wrote 0 bytes | | Attempting to read NT_ARM_FPMR::fpmr | GETREGSET(nt=0x40e len=8) read 8 bytes | Read NT_ARM_FPMR::fpmr = 0xffff800083963d50

After this patch:

| ./fpmr-test | Attempting to write NT_ARM_FPMR::fpmr = 0x900d900d900d900d | SETREGSET(nt=0x40e len=8) wrote 8 bytes | | Attempting to read NT_ARM_FPMR::fpmr | GETREGSET(nt=0x40e len=8) read 8 bytes | Read NT_ARM_FPMR::fpmr = 0x900d900d900d900d | | Attempting to write NT_ARM_FPMR (zero length) | SETREGSET(nt=0x40e len=0) wrote 0 bytes | | Attempting to read NT_ARM_FPMR::fpmr | GETREGSET(nt=0x40e len=8) read 8 bytes | Read NT_ARM_FPMR::fpmr = 0x900d900d900d900d

Reference

https://git.kernel.org/stable/c/8ab73c34e3c5b580721696665eabd799346bc50b https://git.kernel.org/stable/c/f5d71291841aecfe5d8435da2dfa7f58ccd18bc8

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