From: Eugene Shatokhin Date: Tue, 17 Mar 2015 10:09:18 +0000 (+0900) Subject: kprobes/x86: Return correct length in __copy_instruction() X-Git-Tag: v3.12.45~59 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=b7889b59bcb13c97329f5c639b89bf4673b8ae1c;p=thirdparty%2Fkernel%2Fstable.git kprobes/x86: Return correct length in __copy_instruction() commit c80e5c0c23ce2282476fdc64c4b5e3d3a40723fd upstream. On x86-64, __copy_instruction() always returns 0 (error) if the instruction uses %rip-relative addressing. This is because kernel_insn_init() is called the second time for 'insn' instance in such cases and sets all its fields to 0. Because of this, trying to place a kprobe on such instruction will fail, register_kprobe() will return -EINVAL. This patch fixes the problem. Signed-off-by: Eugene Shatokhin Signed-off-by: Masami Hiramatsu Link: http://lkml.kernel.org/r/20150317100918.28349.94654.stgit@localhost.localdomain Signed-off-by: Ingo Molnar Signed-off-by: Jiri Slaby --- diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c index a1f5b1866cbe4..490fee15fea56 100644 --- a/arch/x86/kernel/kprobes/core.c +++ b/arch/x86/kernel/kprobes/core.c @@ -326,13 +326,16 @@ int __kprobes __copy_instruction(u8 *dest, u8 *src) { struct insn insn; kprobe_opcode_t buf[MAX_INSN_SIZE]; + int length; kernel_insn_init(&insn, (void *)recover_probed_instruction(buf, (unsigned long)src)); insn_get_length(&insn); + length = insn.length; + /* Another subsystem puts a breakpoint, failed to recover */ if (insn.opcode.bytes[0] == BREAKPOINT_INSTRUCTION) return 0; - memcpy(dest, insn.kaddr, insn.length); + memcpy(dest, insn.kaddr, length); #ifdef CONFIG_X86_64 if (insn_rip_relative(&insn)) { @@ -362,7 +365,7 @@ int __kprobes __copy_instruction(u8 *dest, u8 *src) *(s32 *) disp = (s32) newdisp; } #endif - return insn.length; + return length; } static int __kprobes arch_copy_kprobe(struct kprobe *p)