linux-kernel - [tip: refs/heads/perf/core] kprobes: Prohibit probing on BUG() and WARN() address

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Message-ID: <156771659359.12994.2378632133614050120.tip-bot2@tip-bot2>
Date:   Thu, 05 Sep 2019 20:49:53 -0000
From:   "tip-bot2 for Masami Hiramatsu" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Ingo Molnar <mingo@...nel.org>, Borislav Petkov <bp@...en8.de>,
        linux-kernel@...r.kernel.org
Subject: [tip: refs/heads/perf/core] kprobes: Prohibit probing on BUG() and
 WARN() address

The following commit has been merged into the refs/heads/perf/core branch of tip:

Commit-ID:     e336b4027775cb458dc713745e526fa1a1996b2a
Gitweb:        https://git.kernel.org/tip/e336b4027775cb458dc713745e526fa1a1996b2a
Author:        Masami Hiramatsu <mhiramat@...nel.org>
AuthorDate:    Tue, 03 Sep 2019 20:08:21 +09:00
Committer:     Ingo Molnar <mingo@...nel.org>
CommitterDate: Thu, 05 Sep 2019 10:15:16 +02:00

kprobes: Prohibit probing on BUG() and WARN() address

Since BUG() and WARN() may use a trap (e.g. UD2 on x86) to
get the address where the BUG() has occurred, kprobes can not
do single-step out-of-line that instruction. So prohibit
probing on such address.

Without this fix, if someone put a kprobe on WARN(), the
kernel will crash with invalid opcode error instead of
outputing warning message, because kernel can not find
correct bug address.

Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
Acked-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
Acked-by: Naveen N. Rao <naveen.n.rao@...ux.vnet.ibm.com>
Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>
Cc: David S . Miller <davem@...emloft.net>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Naveen N . Rao <naveen.n.rao@...ux.ibm.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Link: https://lkml.kernel.org/r/156750890133.19112.3393666300746167111.stgit@devnote2
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 include/linux/bug.h | 5 +++++
 kernel/kprobes.c    | 3 ++-
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/include/linux/bug.h b/include/linux/bug.h
index fe59165..f639bd0 100644
--- a/include/linux/bug.h
+++ b/include/linux/bug.h
@@ -47,6 +47,11 @@ void generic_bug_clear_once(void);
 
 #else	/* !CONFIG_GENERIC_BUG */
 
+static inline void *find_bug(unsigned long bugaddr)
+{
+	return NULL;
+}
+
 static inline enum bug_trap_type report_bug(unsigned long bug_addr,
 					    struct pt_regs *regs)
 {
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index d9770a5..ebe8315 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -1514,7 +1514,8 @@ static int check_kprobe_address_safe(struct kprobe *p,
 	/* Ensure it is not in reserved area nor out of text */
 	if (!kernel_text_address((unsigned long) p->addr) ||
 	    within_kprobe_blacklist((unsigned long) p->addr) ||
-	    jump_label_text_reserved(p->addr, p->addr)) {
+	    jump_label_text_reserved(p->addr, p->addr) ||
+	    find_bug((unsigned long)p->addr)) {
 		ret = -EINVAL;
 		goto out;
 	}