openkylin
/
platform_system_core
mirror of https://gitee.com/openkylin/platform_system_core.git
9
0
Fork 0
Code Issues Projects Releases Wiki Activity

logd: iterator corruption paranoia 

Add checking for impossible(tm) scenarios within LogBuffer::flushTo:

1) When iterating through the log entries, check if the iterator
   returns two identical element references and break out of the loop.
2) Cap the maximum number of log entries we will skip while holding
   the iterator lock at 4194304, break out of the loop.

We print a message to the kernel logs if we hit these cases.

ToDo: Remove this paranoia at some future date.

Test: gTest liblog-unit-tests logcat-unit-tests and logd-unit-tests
Bug: 37378309
Change-Id: I789594649db14093238828b9f6d1daeca8b780c2
This commit is contained in:
Mark Salyzyn 2017-04-17 12:46:12 -07:00
parent 5836379b21
commit 3614a0c5d4
1 changed files with 14 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

14
logd/LogBuffer.cpp
View File

@ -1118,9 +1118,22 @@ log_time LogBuffer::flushTo(SocketClient* reader, const log_time& start,
log_time max = start;
LogBufferElement* lastElement = nullptr; // iterator corruption paranoia
static const size_t maxSkip = 4194304; // maximum entries to skip
size_t skip = maxSkip;
for (; it != mLogElements.end(); ++it) {
LogBufferElement* element = *it;
if (!--skip) {
android::prdebug("reader.per: too many elements skipped");
break;
}
if (element == lastElement) {
android::prdebug("reader.per: identical elements");
break;
}
lastElement = element;
if (!privileged && (element->getUid() != uid)) {
continue;
}
@ -1165,6 +1178,7 @@ log_time LogBuffer::flushTo(SocketClient* reader, const log_time& start,
return max;
}
skip = maxSkip;
pthread_mutex_lock(&mLogElementsLock);
}
pthread_mutex_unlock(&mLogElementsLock);