[PATCH AUTOSEL 4.9 48/60] kprobes: Prohibit probing on BUG() and WARN() address

[Sasha Levin <sashal@kernel.org>]

From: Masami Hiramatsu <mhiramat@kernel.org>

[ Upstream commit e336b4027775cb458dc713745e526fa1a1996b2a ]

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@kernel.org>
Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Acked-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Cc: David S . Miller <davem@davemloft.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Naveen N . Rao <naveen.n.rao@linux.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/156750890133.19112.3393666300746167111.stgit@devnote2
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.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 292d6a10b0c26..0faae96302bda 100644
--- a/include/linux/bug.h
+++ b/include/linux/bug.h
@@ -114,6 +114,11 @@ int is_valid_bugaddr(unsigned long addr);
 
 #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 e2845dd53b30b..11863e2b01c25 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -1454,7 +1454,8 @@ 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;
 	}
-- 
2.20.1