From: Nadav Amit <nadav.amit@gmail.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
x86@kernel.org, linux-kernel@vger.kernel.org,
Nadav Amit <namit@vmware.com>,
Masami Hiramatsu <mhiramat@kernel.org>,
Peter Zijlstra <peterz@infradead.org>
Subject: [PATCH] x86/kprobes: Fix 1 byte conditional jump target
Date: Sat, 4 Feb 2023 21:08:07 +0000 [thread overview]
Message-ID: <20230204210807.3930-1-namit@vmware.com> (raw)
From: Nadav Amit <namit@vmware.com>
Commit 3bc753c06dd0 ("kbuild: treat char as always unsigned") broke
kprobes. Setting a probe-point on 1 byte conditional jump can cause the
kernel to crash, as the branch target is not sign extended.
Fix by using s8 instead of char and use immediate.value instead of
immediate.bytes for consistency.
Cc: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Nadav Amit <namit@vmware.com>
---
arch/x86/kernel/kprobes/core.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c
index b36f3c367cb2..6a56d56b3817 100644
--- a/arch/x86/kernel/kprobes/core.c
+++ b/arch/x86/kernel/kprobes/core.c
@@ -625,7 +625,7 @@ static int prepare_emulation(struct kprobe *p, struct insn *insn)
/* 1 byte conditional jump */
p->ainsn.emulate_op = kprobe_emulate_jcc;
p->ainsn.jcc.type = opcode & 0xf;
- p->ainsn.rel32 = *(char *)insn->immediate.bytes;
+ p->ainsn.rel32 = *(s8 *)&insn->immediate.value;
break;
case 0x0f:
opcode = insn->opcode.bytes[1];
--
2.34.1
next reply other threads:[~2023-02-04 21:08 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-04 21:08 Nadav Amit [this message]
2023-02-05 7:49 ` [PATCH] x86/kprobes: Fix 1 byte conditional jump target Nadav Amit
2023-02-06 14:19 ` Masami Hiramatsu
2023-02-06 14:18 ` Masami Hiramatsu
2023-02-06 18:42 ` Dave Hansen
2023-02-06 19:05 ` Nadav Amit
2023-02-06 22:38 ` Dave Hansen
2023-02-07 0:54 ` Masami Hiramatsu
2023-02-07 15:21 ` Masami Hiramatsu
2023-02-07 15:33 ` Dave Hansen
2023-02-08 6:34 ` Nadav Amit
2023-02-08 6:56 ` Dave Hansen
2023-02-08 6:58 ` Nadav Amit
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