From: Dianzhang Chen dianzhangchen0@gmail.com
commit 31a2fbb390fee4231281b939e1979e810f945415 upstream.
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 dianzhangchen0@gmail.com Signed-off-by: Thomas Gleixner tglx@linutronix.de 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@gm... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/x86/kernel/ptrace.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)
--- a/arch/x86/kernel/ptrace.c +++ b/arch/x86/kernel/ptrace.c @@ -23,6 +23,7 @@ #include <linux/rcupdate.h> #include <linux/export.h> #include <linux/context_tracking.h> +#include <linux/nospec.h>
#include <asm/uaccess.h> #include <asm/pgtable.h> @@ -697,9 +698,11 @@ static unsigned long ptrace_get_debugreg { 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]; + struct perf_event *bp = thread->ptrace_bps[index]; + index = array_index_nospec(index, HBP_NUM);
if (bp) val = bp->hw.info.address;