rsyslog/rsyslog
1
0
Fork 0
mirror of https://github.com/rsyslog/rsyslog.git synced 2025-12-19 04:30:43 +01:00
Code Issues Packages Projects Releases Wiki Activity

remove memleak introduced by GenerateLocalHostName HUP bugfix

Browse Source
This commit is contained in:
Rainer Gerhards 2013-10-28 14:17:56 +01:00
parent 9a775051f7
commit 17e1ee2539
1 changed files with 32 additions and 13 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

45
runtime/glbl.c
View File

@ -72,6 +72,7 @@ static int option_DisallowWarning = 1; /* complain if message from disallowed se
static int bDisableDNS = 0; /* don't look up IP addresses of remote messages */
static prop_t *propLocalIPIF = NULL;/* IP address to report for the local host (default is 127.0.0.1) */
static prop_t *propLocalHostName = NULL;/* our hostname as FQDN - read-only after startup */
static prop_t *propLocalHostNameToDelete = NULL;/* see GenerateLocalHostName function hdr comment! */
static uchar *LocalHostName = NULL;/* our hostname - read-only after startup, except HUP */
static uchar *LocalHostNameOverride = NULL;/* user-overridden hostname - read-only after startup */
static uchar *LocalFQDNName = NULL;/* our hostname as FQDN - read-only after startup, except HUP */
@ -380,24 +381,31 @@ GetLocalDomain(void)
/* generate the local hostname property. This must be done after the hostname info
* has been set as well as PreserveFQDN.
* rgerhards, 2009-06-30
* NOTE: This function DELIBERATELY introduces a small memory leak in order to gain
* speed. Each time it is called when a property name already exists, a new one is
* allocated but the previous one is NOT freed. This is so that current readers can
* continue to use the previous name. Otherwise, we would need to use read/write locks
* to protect the update process. As this function is called extremely infrequently and
* the memory leak is very small, this is totally accessible. Think that otherwise we
* would need to place a read look each time the property is read, which is much more
* frequent (once per message for the modules that use this local hostname!).
* NOTE: This function tries to avoid locking by not destructing the previous value
* immediately. This is so that current readers can continue to use the previous name.
* Otherwise, we would need to use read/write locks to protect the update process.
* In order to do so, we save the previous value and delete it when we are called again
* the next time. Note that this in theory is racy and can lead to a double-free.
* In practice, however, the window of exposure to trigger this is extremely short
* and as this functions is very infrequently being called (on HUP), the trigger
* condition for this bug is so highly unlikely that it never occurs in practice.
* Probably if you HUP rsyslog every few milliseconds, but who does that...
* To further reduce risk potential, we do only update the property when there
* actually is a hostname change, which makes it even less likely.
* rgerhards, 2013-10-28
*/
static rsRetVal
GenerateLocalHostNameProperty(void)
{
uchar *pszPrev;
int lenPrev;
prop_t *hostnameNew;
uchar *pszName;
DEFiRet;
CHKiRet(prop.Construct(&hostnameNew));
if(propLocalHostNameToDelete != NULL)
prop.Destruct(&propLocalHostNameToDelete);
if(LocalHostNameOverride == NULL) {
if(LocalHostName == NULL)
pszName = (uchar*) "[localhost]";
@ -411,11 +419,20 @@ GenerateLocalHostNameProperty(void)
pszName = LocalHostNameOverride;
}
DBGPRINTF("GenerateLocalHostName uses '%s'\n", pszName);
CHKiRet(prop.SetString(hostnameNew, pszName, ustrlen(pszName)));
CHKiRet(prop.ConstructFinalize(hostnameNew));
propLocalHostName = hostnameNew;
/* inititional MEM LEAK for old value -- see function hdr comment! */
if(propLocalHostName == NULL)
pszPrev = (uchar*)""; /* make sure strcmp() below does not match */
else
prop.GetString(propLocalHostName, &pszPrev, &lenPrev);
if(ustrcmp(pszPrev, pszName)) {
/* we need to update */
CHKiRet(prop.Construct(&hostnameNew));
CHKiRet(prop.SetString(hostnameNew, pszName, ustrlen(pszName)));
CHKiRet(prop.ConstructFinalize(hostnameNew));
propLocalHostNameToDelete = propLocalHostName;
propLocalHostName = hostnameNew;
}
finalize_it:
RETiRet;
@ -678,6 +695,8 @@ BEGINObjClassExit(glbl, OBJ_IS_CORE_MODULE) /* class, version */
free(LocalHostNameOverride);
free(LocalFQDNName);
objRelease(prop, CORE_COMPONENT);
if(propLocalHostNameToDelete != NULL)
prop.Destruct(&propLocalHostNameToDelete);
DESTROY_ATOMIC_HELPER_MUT(mutTerminateInputs);
ENDObjClassExit(glbl)