3.16.76-rc1 review patch. If anyone has any objections, please let me know.
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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 Link: https://lkml.kernel.org/r/1561476617-3759-1-git-send-email-dianzhangchen0@gm... [bwh: Backported to 3.16: fold in fix-up from commit 223cea6a4f05 "Merge branch 'x86-pti-for-linus' of ..."] Signed-off-by: Ben Hutchings ben@decadent.org.uk --- 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 @@ -24,6 +24,7 @@ #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> @@ -707,7 +708,8 @@ static unsigned long ptrace_get_debugreg unsigned long val = 0;
if (n < HBP_NUM) { - struct perf_event *bp = thread->ptrace_bps[n]; + int index = array_index_nospec(n, HBP_NUM); + struct perf_event *bp = thread->ptrace_bps[index];
if (bp) val = bp->hw.info.address;