[PATCH AUTOSEL 4.14 73/89] kprobes: Prohibit probing on BUG() and WARN() address

From: Sasha Levin
Date: Sun Sep 22 2019 - 14:59:16 EST


From: Masami Hiramatsu <mhiramat@xxxxxxxxxx>

[ 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@xxxxxxxxxx>
Acked-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
Acked-by: Naveen N. Rao <naveen.n.rao@xxxxxxxxxxxxxxxxxx>
Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@xxxxxxxxx>
Cc: David S . Miller <davem@xxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Naveen N . Rao <naveen.n.rao@xxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Link: https://lkml.kernel.org/r/156750890133.19112.3393666300746167111.stgit@devnote2
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
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 da4231c905c85..f485974177914 100644
--- a/include/linux/bug.h
+++ b/include/linux/bug.h
@@ -45,6 +45,11 @@ 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 c43bc2bc5b2ca..f7a4602a76f98 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -1501,7 +1501,8 @@ 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