From: Masami Hiramatsu mhiramat@kernel.org
[ Upstream commit 78ff2733ff352175eb7f4418a34654346e1b6cd2 ]
Fix to restore BTF if single-stepping causes a page fault and it is cancelled.
Usually the BTF flag was restored when the single stepping is done (in resume_execution()). However, if a page fault happens on the single stepping instruction, the fault handler is invoked and the single stepping is cancelled. Thus, the BTF flag is not restored.
Fixes: 1ecc798c6764 ("x86: debugctlmsr kprobes") Signed-off-by: Masami Hiramatsu mhiramat@kernel.org Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Link: https://lkml.kernel.org/r/160389546985.106936.12727996109376240993.stgit@dev... Signed-off-by: Sasha Levin sashal@kernel.org --- arch/x86/kernel/kprobes/core.c | 5 +++++ 1 file changed, 5 insertions(+)
diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c index 02665ffef0506..700d434f5bda9 100644 --- a/arch/x86/kernel/kprobes/core.c +++ b/arch/x86/kernel/kprobes/core.c @@ -1022,6 +1022,11 @@ int kprobe_fault_handler(struct pt_regs *regs, int trapnr) * So clear it by resetting the current kprobe: */ regs->flags &= ~X86_EFLAGS_TF; + /* + * Since the single step (trap) has been cancelled, + * we need to restore BTF here. + */ + restore_btf();
/* * If the TF flag was set before the kprobe hit,