From 31a2fbb390fee4231281b939e1979e810f945415 Mon Sep 17 00:00:00 2001 From: Dianzhang Chen Date: Tue, 25 Jun 2019 23:30:17 +0800 Subject: [PATCH] x86/ptrace: Fix possible spectre-v1 in ptrace_get_debugreg() The index to access the threads ptrace_bps is controlled by userspace via syscall: sys_ptrace(), hence leading to a potential exploitation of the Spectre variant 1 vulnerability. The index can be controlled from: ptrace -> arch_ptrace -> ptrace_get_debugreg. Fix this by sanitizing the user supplied index before using it access thread->ptrace_bps. Signed-off-by: Dianzhang Chen Signed-off-by: Thomas Gleixner Cc: bp@alien8.de Cc: hpa@zytor.com Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/1561476617-3759-1-git-send-email-dianzhangchen0@gmail.com --- arch/x86/kernel/ptrace.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c index a166c960bc9e..cbac64659dc4 100644 --- a/arch/x86/kernel/ptrace.c +++ b/arch/x86/kernel/ptrace.c @@ -25,6 +25,7 @@ #include #include #include +#include #include #include @@ -643,9 +644,11 @@ static unsigned long ptrace_get_debugreg(struct task_struct *tsk, int n) { struct thread_struct *thread = &tsk->thread; unsigned long val = 0; + int index = n; if (n < HBP_NUM) { - struct perf_event *bp = thread->ptrace_bps[n]; + index = array_index_nospec(index, HBP_NUM); + struct perf_event *bp = thread->ptrace_bps[index]; if (bp) val = bp->hw.info.address; -- 2.11.0