On Tue, May 19, 2015 at 04:58:14PM +0300, Eugene Shatokhin wrote:
> Commit c80e5c0c23ce2282476fdc64c4b5e3d3a40723fd upstream.
> This is the backport of that fix for 3.16.y-3.18.y.
>
Thank you, Eugene. I'll queue this for the 3.16 kernel.
Cheers,
--
Luís
> 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 <eugene.shatokhin@xxxxxxxxxx>
> ---
> arch/x86/kernel/kprobes/core.c | 7 +++++--
> 1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c
> index 93d2c04..f2e281c 100644
> --- a/arch/x86/kernel/kprobes/core.c
> +++ b/arch/x86/kernel/kprobes/core.c
> @@ -330,13 +330,16 @@ int __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)) {
> @@ -366,7 +369,7 @@ int __copy_instruction(u8 *dest, u8 *src)
> *(s32 *) disp = (s32) newdisp;
> }
> #endif
> - return insn.length;
> + return length;
> }
>
> static int arch_copy_kprobe(struct kprobe *p)
> --
> 2.3.2
>
> --
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