Commit dec8784c authored by Masami Hiramatsu (Google)'s avatar Masami Hiramatsu (Google) Committed by Ingo Molnar
Browse files

x86/kprobes: Update kcb status flag after singlestepping 



Fix kprobes to update kcb (kprobes control block) status flag to
KPROBE_HIT_SSDONE even if the kp->post_handler is not set.

This bug may cause a kernel panic if another INT3 user runs right
after kprobes because kprobe_int3_handler() misunderstands the
INT3 is kprobe's single stepping INT3.

Fixes: 6256e668 ("x86/kprobes: Use int3 instead of debug trap for single-step")
Reported-by: default avatarDaniel Müller <deso@posteo.net>
Signed-off-by: default avatarMasami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Tested-by: default avatarDaniel Müller <deso@posteo.net>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/all/20220727210136.jjgc3lpqeq42yr3m@muellerd-fedora-PC2BDTX9
Link: https://lore.kernel.org/r/165942025658.342061.12452378391879093249.stgit@devnote2
parent 28f6c37a

arch/x86/kernel/kprobes/core.c

+11 −7
Original line number Diff line number Diff line
@@ -814,17 +814,21 @@ set_current_kprobe(struct kprobe *p, struct pt_regs *regs, 
static void kprobe_post_process(struct kprobe *cur, struct pt_regs *regs,

			       struct kprobe_ctlblk *kcb)

{

	if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {

		kcb->kprobe_status = KPROBE_HIT_SSDONE;

		cur->post_handler(cur, regs, 0);

	}



	/* Restore back the original saved kprobes variables and continue. */

	if (kcb->kprobe_status == KPROBE_REENTER)

	if (kcb->kprobe_status == KPROBE_REENTER) {

		/* This will restore both kcb and current_kprobe */

		restore_previous_kprobe(kcb);

	else

	} else {

		/*

		 * Always update the kcb status because

		 * reset_curent_kprobe() doesn't update kcb.

		 */

		kcb->kprobe_status = KPROBE_HIT_SSDONE;

		if (cur->post_handler)

			cur->post_handler(cur, regs, 0);

		reset_current_kprobe();

	}

}

NOKPROBE_SYMBOL(kprobe_post_process);



static void setup_singlestep(struct kprobe *p, struct pt_regs *regs,