linux-kernel - [PATCH 5.10 8/9] x86/kprobes: Update kcb status flag after singlestepping

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Date:   Wed, 5 Jul 2023 14:46:52 +0800
From:   Li Huafei <lihuafei1@...wei.com>
To:     <stable@...r.kernel.org>
CC:     <gregkh@...uxfoundation.org>, <mhiramat@...nel.org>,
        <tglx@...utronix.de>, <mingo@...hat.com>, <bp@...en8.de>,
        <x86@...nel.org>, <hpa@...or.com>, <sashal@...nel.org>,
        <peterz@...radead.org>, <linux-kernel@...r.kernel.org>,
        <xukuohai@...wei.com>, <natechancellor@...il.com>,
        <ndesaulniers@...gle.com>, <rostedt@...dmis.org>,
        <weiyongjun1@...wei.com>, <gustavoars@...nel.org>,
        <namit@...are.com>, <laijs@...ux.alibaba.com>,
        <clang-built-linux@...glegroups.com>, <lihuafei1@...wei.com>
Subject: [PATCH 5.10 8/9] x86/kprobes: Update kcb status flag after singlestepping

From: "Masami Hiramatsu (Google)" <mhiramat@...nel.org>

[ Upstream commit dec8784c9088b131a1523f582c2194cfc8107dc0 ]

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: 6256e668b7af ("x86/kprobes: Use int3 instead of debug trap for single-step")
Reported-by: Daniel Müller <deso@...teo.net>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Tested-by: Daniel Müller <deso@...teo.net>
Cc: stable@...r.kernel.org
Link: https://lore.kernel.org/all/20220727210136.jjgc3lpqeq42yr3m@muellerd-fedora-PC2BDTX9
Link: https://lore.kernel.org/r/165942025658.342061.12452378391879093249.stgit@devnote2
Signed-off-by: Li Huafei <lihuafei1@...wei.com>
---
 arch/x86/kernel/kprobes/core.c | 18 +++++++++++-------
 1 file changed, 11 insertions(+), 7 deletions(-)

diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c
index 07f222743811..bde43592f54a 100644
--- a/arch/x86/kernel/kprobes/core.c
+++ b/arch/x86/kernel/kprobes/core.c
@@ -826,16 +826,20 @@ NOKPROBE_SYMBOL(arch_prepare_kretprobe);
 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);
 
-- 
2.17.1