[BUGFIX PATCH] tracing/kprobes: Fix within_notrace_func() to check only notrace functions

From: Masami Hiramatsu
Date: Thu Aug 02 2018 - 12:02:32 EST

Fix within_notrace_func() to check only notrace functions
and to ignore the kprobe-event which can not solve symbol

within_notrace_func() returns true if the given kprobe events
probe point seems like out-of-range. But that is not correct
place to check it, it should be done in kprobes afterwards.

kprobe-events allows user to define a probe point on "currently
unloaded module" so that it can trace the event while module
load. In this case, user will put a probe on a symbol which
is not in kallsyms yet and it hits the within_notrace_func().
In the result, kprobe-events always refuses if user defines
a probe on "currenly unloaded module".

Fixes: commit 45408c4f9250 ("tracing: kprobes: Prohibit probing on notrace function")
Signed-off-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
kernel/trace/trace_kprobe.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index deeb03ae21e1..2e13f77b9a37 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -88,6 +88,7 @@ static nokprobe_inline unsigned long trace_kprobe_nhit(struct trace_kprobe *tk)
return nhit;

+/* Return 0 if it fails to find the symbol address */
static nokprobe_inline
unsigned long trace_kprobe_address(struct trace_kprobe *tk)
@@ -96,7 +97,8 @@ unsigned long trace_kprobe_address(struct trace_kprobe *tk)
if (tk->symbol) {
addr = (unsigned long)
- addr += tk->rp.kp.offset;
+ if (addr)
+ addr += tk->rp.kp.offset;
} else {
addr = (unsigned long)tk->rp.kp.addr;
@@ -519,8 +521,8 @@ static bool within_notrace_func(struct trace_kprobe *tk)
unsigned long offset, size, addr;

addr = trace_kprobe_address(tk);
- if (!kallsyms_lookup_size_offset(addr, &size, &offset))
- return true; /* Out of range. */
+ if (!addr || !kallsyms_lookup_size_offset(addr, &size, &offset))
+ return false;

return !ftrace_location_range(addr - offset, addr - offset + size);