[PATCH 2/2] perf/x86/regs: Check reserved bits

From: kan . liang
Date: Thu May 23 2019 - 14:40:52 EST


From: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>

The perf fuzzer triggers a warning which map to:

if (WARN_ON_ONCE(idx >= ARRAY_SIZE(pt_regs_offset)))
return 0;

The bits between XMM registers and generic registers are reserved.
But perf_reg_validate() doesn't check these bits.

Add REG_RESERVED for reserved bits.
Check the reserved bits in perf_reg_validate().

Fixes: 878068ea270e ("perf/x86: Support outputting XMM registers")
Reported-by: Vince Weaver <vincent.weaver@xxxxxxxxx>
Signed-off-by: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>
---
arch/x86/kernel/perf_regs.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/perf_regs.c b/arch/x86/kernel/perf_regs.c
index 86ffe5a..3f8c1fc 100644
--- a/arch/x86/kernel/perf_regs.c
+++ b/arch/x86/kernel/perf_regs.c
@@ -79,6 +79,9 @@ u64 perf_reg_value(struct pt_regs *regs, int idx)
return regs_get_register(regs, pt_regs_offset[idx]);
}

+#define REG_RESERVED (((1ULL << PERF_REG_X86_XMM0) - 1) & \
+ ~((1ULL << PERF_REG_X86_MAX) - 1))
+
#ifdef CONFIG_X86_32
#define REG_NOSUPPORT ((1ULL << PERF_REG_X86_R8) | \
(1ULL << PERF_REG_X86_R9) | \
@@ -91,7 +94,7 @@ u64 perf_reg_value(struct pt_regs *regs, int idx)

int perf_reg_validate(u64 mask)
{
- if (!mask || (mask & REG_NOSUPPORT))
+ if (!mask || (mask & (REG_NOSUPPORT | REG_RESERVED)))
return -EINVAL;

return 0;
@@ -117,7 +120,7 @@ void perf_get_regs_user(struct perf_regs *regs_user,

int perf_reg_validate(u64 mask)
{
- if (!mask || (mask & REG_NOSUPPORT))
+ if (!mask || (mask & (REG_NOSUPPORT | REG_RESERVED)))
return -EINVAL;

return 0;
--
2.7.4