[PATCH] x86/optprobe: Fix OPTPROBE vs UACCESS

Peter Zijlstra
2020-03-05T09:21:37Z

arch/x86/kernel/kprobes/opt.c | 14 ++++++++++++++
2 files changed, 15 insertions(+)

diff --git a/arch/x86/include/asm/kprobes.h b/arch/x86/include/asm/kprobes.h
index 95b1f053bd96..073eb7ad2f56 100644
--- a/arch/x86/include/asm/kprobes.h
+++ b/arch/x86/include/asm/kprobes.h
@@ -36,6 +36,7 @@ typedef u8 kprobe_opcode_t;

/* optinsn template addresses */
extern __visible kprobe_opcode_t optprobe_template_entry[];
+extern __visible kprobe_opcode_t optprobe_template_clac[];
extern __visible kprobe_opcode_t optprobe_template_val[];
extern __visible kprobe_opcode_t optprobe_template_call[];
extern __visible kprobe_opcode_t optprobe_template_end[];
diff --git a/arch/x86/kernel/kprobes/opt.c b/arch/x86/kernel/kprobes/opt.c
index 3f45b5c43a71..7a3416c9d0dc 100644
--- a/arch/x86/kernel/kprobes/opt.c
+++ b/arch/x86/kernel/kprobes/opt.c
@@ -92,6 +92,9 @@ asm (
/* We don't bother saving the ss register */
" pushq %rsp\n"
" pushfq\n"
+ ".global optprobe_template_clac\n"
+ "optprobe_template_clac:\n"
+ ASM_NOP3
SAVE_REGS_STRING
" movq %rsp, %rsi\n"
".global optprobe_template_val\n"
@@ -111,6 +114,9 @@ asm (
#else /* CONFIG_X86_32 */
" pushl %esp\n"
" pushfl\n"
+ ".global optprobe_template_clac\n"
+ "optprobe_template_clac:\n"
+ ASM_NOP3
SAVE_REGS_STRING
" movl %esp, %edx\n"
".global optprobe_template_val\n"
@@ -134,6 +140,8 @@ asm (
void optprobe_template_func(void);
STACK_FRAME_NON_STANDARD(optprobe_template_func);

+#define TMPL_CLAC_IDX \
+ ((long)optprobe_template_clac - (long)optprobe_template_entry)
#define TMPL_MOVE_IDX \
((long)optprobe_template_val - (long)optprobe_template_entry)
#define TMPL_CALL_IDX \
@@ -389,6 +397,12 @@ int arch_prepare_optimized_kprobe(struct optimized_kprobe *op,
op->optinsn.size = ret;
len = TMPL_END_IDX + op->optinsn.size;

+ if (static_cpu_has(X86_FEATURE_SMAP)) {
+ buf[TMPL_CLAC_IDX+0] = 0x0f;
+ buf[TMPL_CLAC_IDX+1] = 0x01;
+ buf[TMPL_CLAC_IDX+2] = 0xca;
+ }