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

[Masami Hiramatsu]

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

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 <mhira...@kernel.org>
---
 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)
                        kallsyms_lookup_name(trace_kprobe_symbol(tk));
-               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);
 }