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@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>

2 files changed, 7 insertions, 1 deletions

diff --git a/include/linux/bug.h b/include/linux/bug.h
index fe5916550da8..f639bd0122f3 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 d9770a5393c8..ebe8315a756a 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;
         }