x86: fix jprobe_saved_sp handling

PATCH New Harvey Harrison 1 participant 1 message Dec 17, 2007 x86

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Harvey Harrison

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2007-12-17 21:27 UTC #0 lore raw

PATCH 1/4 x86: fix jprobe_saved_sp handling

This patch fixes a bug of jprobe and cleans up. jprobe for x86-64 can cause kernel page fault when the jprobe_return() is called from incorrect function. Anyway, that path finally invokes BUG() macro, so this is not so serious.

Based on patch from Masami Hiramatsu <[email protected]>

- Use jprobe_saved_regs instead getting it from stack. (Especially on x86-64, it may get incorrect data, because pt_regs can not be get by using container_of(rsp))
- Change the type of stack pointer to unsigned long *.

Signed-off-by Harvey Harrison <[email protected]>

---
 arch/x86/kernel/kprobes.c |    8 ++------
 include/asm-x86/kprobes.h |    2 +-
 2 files changed, 3 insertions(+), 7 deletions(-)

arch/x86/kernel/kprobes.c +2 -6

index e5b7d07..9130c01 100644
@@ -1022,16 +1022,12 @@ int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
 	if ((addr > (u8 *) jprobe_return) && (addr < (u8 *) jprobe_return_end)) {
 #ifdef CONFIG_X86_32
 		if (&regs->sp != kcb->jprobe_saved_sp) {
-			struct pt_regs *saved_regs =
-			    container_of(kcb->jprobe_saved_sp,
-					    struct pt_regs, sp);
+			struct pt_regs *saved_regs = &kcb->jprobe_saved_sp;
 			printk("current sp %p does not match saved sp %p\n",
 			       &regs->sp, kcb->jprobe_saved_sp);
 #else
 		if ((long *)regs->sp != kcb->jprobe_saved_sp) {
-			struct pt_regs *saved_regs =
-			    container_of(kcb->jprobe_saved_sp,
-					    struct pt_regs, sp);
+			struct pt_regs *saved_regs = &kcb->jprobe_saved_sp;
 			printk("current sp %p does not match saved sp %p\n",
 			       (long *)regs->sp, kcb->jprobe_saved_sp);
 #endif

include/asm-x86/kprobes.h +1 -1

index e348ed6..7319c62 100644
@@ -79,7 +79,7 @@ struct kprobe_ctlblk {
 	unsigned long kprobe_status;
 	unsigned long kprobe_old_flags;
 	unsigned long kprobe_saved_flags;
-	long *jprobe_saved_sp;
+	unsigned long *jprobe_saved_sp;
 	struct pt_regs jprobe_saved_regs;
 	kprobe_opcode_t jprobes_stack[MAX_STACK_SIZE];
 	struct prev_kprobe prev_kprobe;

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