From: Nadav Amit namit@vmware.com
commit 8924779df820c53875abaeb10c648e9cb75b46d4 upstream.
When kprobes emulates JNG/JNLE instructions on x86 it uses the wrong condition. For JNG (opcode: 0F 8E), according to Intel SDM, the jump is performed if (ZF == 1 or SF != OF). However the kernel emulation currently uses 'and' instead of 'or'.
As a result, setting a kprobe on JNG/JNLE might cause the kernel to behave incorrectly whenever the kprobe is hit.
Fix by changing the 'and' to 'or'.
Fixes: 6256e668b7af ("x86/kprobes: Use int3 instead of debug trap for single-step") Signed-off-by: Nadav Amit namit@vmware.com Signed-off-by: Ingo Molnar mingo@kernel.org Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20220813225943.143767-1-namit@vmware.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/kernel/kprobes/core.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/arch/x86/kernel/kprobes/core.c +++ b/arch/x86/kernel/kprobes/core.c @@ -495,7 +495,7 @@ static void kprobe_emulate_jcc(struct kp match = ((regs->flags & X86_EFLAGS_SF) >> X86_EFLAGS_SF_BIT) ^ ((regs->flags & X86_EFLAGS_OF) >> X86_EFLAGS_OF_BIT); if (p->ainsn.jcc.type >= 0xe) - match = match && (regs->flags & X86_EFLAGS_ZF); + match = match || (regs->flags & X86_EFLAGS_ZF); } __kprobe_emulate_jmp(p, regs, (match && !invert) || (!match && invert)); }