libutils: Don't segfault ProcessCallStack when getting thread name fails

There's an inherent race in trying to read out the thread name from
the system and the thread closing out on its own (and thus being removed
from procfs).

Try to handle this by formatting the thread name unconditionally with
the tid when getting the thread name fails (instead of dereferencing
NULL and crashing).

Bug: 15406837
Change-Id: Ibf2208b8ce345589e7e9c57e6a307728d1121c5d

1 files changed, 5 insertions, 0 deletions

diff --git a/libutils/ProcessCallStack.cpp b/libutils/ProcessCallStack.cpp
index f837bcb63..db07e563f 100644
--- a/libutils/ProcessCallStack.cpp
+++ b/libutils/ProcessCallStack.cpp
@@ -90,6 +90,11 @@ static String8 getThreadName(pid_t tid) {
         ALOGE("%s: Failed to open %s", __FUNCTION__, path);
     }
 
+    if (procName == NULL) {
+        // Reading /proc/self/task/%d/comm failed due to a race
+        return String8::format("[err-unknown-tid-%d]", tid);
+    }
+
     // Strip ending newline
     strtok(procName, "\n");