Messages in this thread Patch in this message | | | Date | Tue, 23 Mar 2021 15:15:09 -0000 | From | "tip-bot2 for Masami Hiramatsu" <> | Subject | [tip: x86/core] x86/kprobes: Retrieve correct opcode for group instruction |
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The following commit has been merged into the x86/core branch of tip:
Commit-ID: d60ad3d46f1d04a282c56159f1deb675c12733fd Gitweb: https://git.kernel.org/tip/d60ad3d46f1d04a282c56159f1deb675c12733fd Author: Masami Hiramatsu <mhiramat@kernel.org> AuthorDate: Wed, 03 Mar 2021 00:25:24 +09:00 Committer: Peter Zijlstra <peterz@infradead.org> CommitterDate: Tue, 23 Mar 2021 16:07:55 +01:00
x86/kprobes: Retrieve correct opcode for group instruction
Since the opcodes start from 0xff are group5 instruction group which is not 2 bytes opcode but the extended opcode determined by the MOD/RM byte.
The commit abd82e533d88 ("x86/kprobes: Do not decode opcode in resume_execution()") used insn->opcode.bytes[1], but that is not correct. We have to refer the insn->modrm.bytes[1] instead.
Fixes: abd82e533d88 ("x86/kprobes: Do not decode opcode in resume_execution()") Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/161469872400.49483.18214724458034233166.stgit@devnote2 --- arch/x86/kernel/kprobes/core.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c index 60a540f..9b31790 100644 --- a/arch/x86/kernel/kprobes/core.c +++ b/arch/x86/kernel/kprobes/core.c @@ -453,7 +453,11 @@ static void set_resume_flags(struct kprobe *p, struct insn *insn) break; #endif case 0xff: - opcode = insn->opcode.bytes[1]; + /* + * Since the 0xff is an extended group opcode, the instruction + * is determined by the MOD/RM byte. + */ + opcode = insn->modrm.bytes[0]; if ((opcode & 0x30) == 0x10) { /* * call absolute, indirect
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