tracing/kprobes: Fix within_notrace_func() to check only notrace functions

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

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

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

Fixes: commit 45408c4f9250 ("tracing: kprobes: Prohibit probing on notrace function")
Link: http://lkml.kernel.org/r/153319624799.29007.13604430345640129926.stgit@devbox

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

1 files 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);
 }