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Bug 1399520 - Avoid race condition. r=dragana

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MozReview-Commit-ID: 6Pd2HXqBgX4
This commit is contained in:
Liang-Heng Chen 2017-10-19 22:29:41 -04:00
parent 7746cd0200
commit b4603106d0
2 changed files with 23 additions and 11 deletions
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26
modules/libjar/nsJAR.cpp
View File

@ -43,11 +43,27 @@ NS_IMPL_QUERY_INTERFACE(nsJAR, nsIZipReader)
NS_IMPL_ADDREF(nsJAR)
// Custom Release method works with nsZipReaderCache...
// Release might be called from multi-thread, we have to
// take this function carefully to avoid delete-after-use.
MozExternalRefCountType nsJAR::Release(void)
{
nsrefcnt count;
NS_PRECONDITION(0 != mRefCnt, "dup release");
count = --mRefCnt;
RefPtr<nsZipReaderCache> cache;
if (mRefCnt == 2) { // don't use a lock too frequently
// Use a mutex here to guarantee mCache is not racing and the target instance
// is still valid to increase ref-count.
MutexAutoLock lock(mLock);
cache = mCache;
mCache = nullptr;
}
if (cache) {
DebugOnly<nsresult> rv = cache->ReleaseZip(this);
MOZ_ASSERT(NS_SUCCEEDED(rv), "failed to release zip file");
}
count = --mRefCnt; // don't access any member variable after this line
NS_LOG_RELEASE(this, count, "nsJAR");
if (0 == count) {
mRefCnt = 1; /* stabilize */
@ -56,13 +72,7 @@ MozExternalRefCountType nsJAR::Release(void)
delete this;
return 0;
}
if (1 == count && mCache) {
#ifdef DEBUG
nsresult rv =
#endif
mCache->ReleaseZip(this);
NS_ASSERTION(NS_SUCCEEDED(rv), "failed to release zip file");
}
return count;
}

8
modules/libjar/nsJAR.h
View File

@ -12,6 +12,7 @@
#include "mozilla/Logging.h"
#include "prinrval.h"
#include "mozilla/Atomics.h"
#include "mozilla/Mutex.h"
#include "nsIComponentManager.h"
#include "nsCOMPtr.h"
@ -75,8 +76,9 @@ class nsJAR final : public nsIZipReader
mReleaseTime = PR_INTERVAL_NO_TIMEOUT;
}
void SetZipReaderCache(nsZipReaderCache* cache) {
mCache = cache;
void SetZipReaderCache(nsZipReaderCache* aCache) {
mozilla::MutexAutoLock lock(mLock);
mCache = aCache;
}
nsresult GetNSPRFileDesc(PRFileDesc** aNSPRFileDesc);
@ -89,7 +91,7 @@ class nsJAR final : public nsIZipReader
RefPtr<nsZipArchive> mZip; // The underlying zip archive
PRIntervalTime mReleaseTime; // used by nsZipReaderCache for flushing entries
nsZipReaderCache* mCache; // if cached, this points to the cache it's contained in
mozilla::Mutex mLock;
mozilla::Mutex mLock; // protect mCache and mZip
int64_t mMtime;
bool mOpened;
bool mIsOmnijar;