From: Masami Hiramatsu <mhira...@kernel.org>

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 <mhira...@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rost...@goodmis.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);
 }
-- 
2.18.0


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