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mirror of https://github.com/pgbackrest/pgbackrest.git synced 2024-12-14 10:13:05 +02:00

Add memContextCallbackClear() to prevent double free() calls.

If an object free() method was called manually when a callback was set then the callback would call free() again.  This meant that each free() method had to protect against a subsequent call.

Instead, clear the callback (if present) before calling memContextFree().  This is faster (since there is no unecessary callback) and removes the need for semaphores to protect against a double free().
This commit is contained in:
David Steele 2018-11-07 08:51:32 -05:00
parent 48d2795f31
commit a9feaba9e5
12 changed files with 51 additions and 20 deletions

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@ -90,6 +90,10 @@
<p>Change <code>infoArchiveCheckPg()</code> to display the <postgres/> version as a string (e.g. 9.4) instead of the integer representation (e.g. 90400) when throwing an error.</p>
</release-item>
<release-item>
<p>Add <code>memContextCallbackClear()</code> to prevent double <code>free()</code> calls.</p>
</release-item>
<release-item>
<p>Merge <file>crypto/random</file> module into <file>crypto/crypto</file>.</p>
</release-item>

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@ -265,6 +265,32 @@ memContextCallback(MemContext *this, void (*callbackFunction)(void *), void *cal
FUNCTION_TEST_RESULT_VOID();
}
/***********************************************************************************************************************************
Clear the mem context callback. This is usually done in the object free method after resources have been freed but before
memContextFree() is called. The goal is to prevent the object free method from being called more than once.
***********************************************************************************************************************************/
void
memContextCallbackClear(MemContext *this)
{
FUNCTION_TEST_BEGIN();
FUNCTION_TEST_PARAM(MEM_CONTEXT, this);
FUNCTION_TEST_ASSERT(this != NULL);
FUNCTION_TEST_END();
// Error if context is not active or freeing
ASSERT(this->state == memContextStateActive || this->state == memContextStateFreeing);
// Top context cannot have a callback
ASSERT(this != memContextTop());
// Clear callback function and argument
this->callbackFunction = NULL;
this->callbackArgument = NULL;
FUNCTION_TEST_RESULT_VOID();
}
/***********************************************************************************************************************************
Allocate memory in the memory context and optionally zero it.
***********************************************************************************************************************************/

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@ -66,6 +66,7 @@ Use the MEM_CONTEXT*() macros when possible rather than implement error-handling
MemContext *memContextNew(const char *name);
void memContextMove(MemContext *this, MemContext *parentNew);
void memContextCallback(MemContext *this, void (*callbackFunction)(void *), void *callbackArgument);
void memContextCallbackClear(MemContext *this);
MemContext *memContextSwitch(MemContext *this);
void memContextFree(MemContext *this);

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@ -107,6 +107,8 @@ regExpFree(RegExp *this)
if (this != NULL)
{
regfree(&this->regExp);
memContextCallbackClear(this->memContext);
memContextFree(this->memContext);
}

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@ -184,7 +184,7 @@ gzipCompressToLog(const GzipCompress *this)
{
return strNewFmt(
"{inputSame: %s, done: %s, flushing: %s, availIn: %u}", cvtBoolToConstZ(this->inputSame), cvtBoolToConstZ(this->done),
cvtBoolToConstZ(this->done), this->stream != NULL ? this->stream->avail_in : 0);
cvtBoolToConstZ(this->done), this->stream->avail_in);
}
/***********************************************************************************************************************************
@ -198,13 +198,11 @@ gzipCompressFree(GzipCompress *this)
FUNCTION_DEBUG_END();
if (this != NULL)
{
if (this->stream != NULL)
{
deflateEnd(this->stream);
this->stream = NULL;
}
memContextCallbackClear(this->memContext);
memContextFree(this->memContext);
}

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@ -159,7 +159,7 @@ gzipDecompressToLog(const GzipDecompress *this)
{
return strNewFmt(
"{inputSame: %s, done: %s, availIn: %u}", cvtBoolToConstZ(this->inputSame), cvtBoolToConstZ(this->done),
this->stream != NULL ? this->stream->avail_in : 0);
this->stream->avail_in);
}
/***********************************************************************************************************************************
@ -173,13 +173,10 @@ gzipDecompressFree(GzipDecompress *this)
FUNCTION_DEBUG_END();
if (this != NULL)
{
if (this->stream != NULL)
{
inflateEnd(this->stream);
this->stream = NULL;
}
memContextCallbackClear(this->memContext);
memContextFree(this->memContext);
}

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@ -291,6 +291,7 @@ cipherBlockFree(CipherBlock *this)
EVP_CIPHER_CTX_cleanup(this->cipherContext);
// Free mem context
memContextCallbackClear(this->memContext);
memContextFree(this->memContext);
FUNCTION_DEBUG_RESULT_VOID();

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@ -218,13 +218,10 @@ cryptoHashFree(CryptoHash *this)
FUNCTION_DEBUG_END();
if (this != NULL)
{
if (this->hashContext != NULL)
{
EVP_MD_CTX_destroy(this->hashContext);
this->hashContext = NULL;
}
memContextCallbackClear(this->memContext);
memContextFree(this->memContext);
}
@ -295,7 +292,6 @@ cryptoHashOneStr(const String *type, String *message)
FUNCTION_TEST_RESULT(BUFFER, cryptoHashOneC(type, (const unsigned char *)strPtr(message), strSize(message)));
}
/***********************************************************************************************************************************
Get hmac for one message/key
***********************************************************************************************************************************/

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@ -250,6 +250,8 @@ storageDriverPosixFileReadFree(StorageDriverPosixFileRead *this)
if (this != NULL)
{
storageDriverPosixFileReadClose(this);
memContextCallbackClear(this->memContext);
memContextFree(this->memContext);
}

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@ -354,6 +354,8 @@ storageDriverPosixFileWriteFree(StorageDriverPosixFileWrite *this)
if (this != NULL)
{
storageDriverPosixFileWriteClose(this);
memContextCallbackClear(this->memContext);
memContextFree(this->memContext);
}

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@ -232,6 +232,10 @@ testRun(void)
memContextCallback(memContext, (MemContextCallback)testFree, memContext),
AssertError, "callback is already set for context 'test-callback'");
// Clear and reset it
memContextCallbackClear(memContext);
memContextCallback(memContext, (MemContextCallback)testFree, memContext);
memContextFree(memContext);
TEST_RESULT_PTR(memContextCallbackArgument, memContext, "callback argument is context");
}

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@ -170,8 +170,6 @@ testRun(void)
decompress->inputSame = true;
decompress->done = true;
inflateEnd(decompress->stream);
decompress->stream = NULL;
TEST_RESULT_STR(strPtr(gzipDecompressToLog(decompress)), "{inputSame: true, done: true, availIn: 0}", "format object");
}