From: Mark Rutland <mark.rutland@arm.com> mainline inclusion from mainline-6.13 commit f5d71291841aecfe5d8435da2dfa7f58ccd18bc8 category: bugfix bugzilla: https://atomgit.com/openeuler/kernel/issues/8904 CVE: NA Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... ---------------------------------------------------------------------- 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 Fixes: 4035c22ef7d4 ("arm64/ptrace: Expose FPMR via ptrace") Cc: <stable@vger.kernel.org> # 6.9.x Signed-off-by: Mark Rutland <mark.rutland@arm.com> Cc: Mark Brown <broonie@kernel.org> Cc: Will Deacon <will@kernel.org> Reviewed-by: Mark Brown <broonie@kernel.org> Link: https://lore.kernel.org/r/20241205121655.1824269-3-mark.rutland@arm.com Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> Signed-off-by: Qinxin Xia <xiaqinxin@huawei.com> Signed-off-by: Hongye Lin <linhongye@h-partners.com> --- arch/arm64/kernel/ptrace.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c index 5543479f8c9c..bc05c0f9f7e1 100644 --- a/arch/arm64/kernel/ptrace.c +++ b/arch/arm64/kernel/ptrace.c @@ -718,6 +718,8 @@ static int fpmr_set(struct task_struct *target, const struct user_regset *regset if (!system_supports_fpmr()) return -EINVAL; + fpmr = target->thread.uw.fpmr; + ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, &fpmr, 0, count); if (ret) return ret; -- 2.33.0