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authorNadav Amit <namit@vmware.com>2023-02-08 07:17:08 +0000
committerDave Hansen <dave.hansen@linux.intel.com>2023-02-08 12:03:27 -0800
commitae052e3ae09572194d7e574906db7272041577d3 (patch)
treeadb6f9271a31518e91964af558284e9f0079fc57 /arch
parent9d2c7203ffdb846399b82b0660563c89e918c751 (diff)
x86/kprobes: Fix 1 byte conditional jump target
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 when the (signed) relative jump offset gets treated as unsigned. Fix by replacing the unsigned 'immediate.bytes' (plus a cast) with the signed 'immediate.value' when assigning to the relative jump offset. [ dhansen: clarified changelog ] Fixes: 3bc753c06dd0 ("kbuild: treat char as always unsigned") Suggested-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> Suggested-by: Dave Hansen <dave.hansen@intel.com> Signed-off-by: Nadav Amit <namit@vmware.com> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lore.kernel.org/all/20230208071708.4048-1-namit%40vmware.com
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/kernel/kprobes/core.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c
index b36f3c367cb2..695873c0f50b 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 = insn->immediate.value;
break;
case 0x0f:
opcode = insn->opcode.bytes[1];