Null-pointer dereference - Revision history

Jmanico: Redirected page to Null Dereference

2014-04-05T18:32:25Z

Redirected page to Null Dereference

Jmanico: Redirected page to Https://www.owasp.org/index.php/Null Dereference

2014-04-05T18:31:31Z

Redirected page to Https://www.owasp.org/index.php/Null Dereference

Jmanico at 18:31, 5 April 2014

2014-04-05T18:31:21Z

Jmanico: Replaced content with "#REDIRECT https://www.owasp.org/index.php/Null_Dereference"

2014-04-05T18:31:08Z

Replaced content with "#REDIRECT https://www.owasp.org/index.php/Null_Dereference"

MediaWiki spam cleanup: Reverting to last version not containing links to www.textlarolbodron.com

2009-05-27T18:28:55Z

Reverting to last version not containing links to www.textlarolbodron.com

Deleted user at 16:31, 22 May 2009

2009-05-22T16:31:48Z

KirstenS at 20:43, 11 April 2009

2009-04-11T20:43:34Z

KirstenS at 01:05, 27 January 2009

2009-01-27T01:05:37Z

KirstenS at 20:40, 26 September 2008

2008-09-26T20:40:59Z

Weilin Zhong at 21:04, 4 August 2006

2006-08-04T21:04:59Z

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−	#REDIRECT ~~[[::Category:Vulnerability]]~~
−
−
−
−	~~==Overview==~~
−
−	~~A null-pointer dereference takes place when a pointer with a value of NULL is used as though it pointed to a valid memory area.~~
−
−	~~==Consequences ==~~
−
−	* Availability: Null-pointer dereferences invariably result in the failure of the process.
−
−	~~==Exposure period ==~~
−
−	* Requirements specification: The choice could be made to use a language that is not susceptible to these issues.
−
−	* Implementation: Proper sanity checks at implementation time can serve to prevent null-pointer dereferences
−
−	~~==Platform ==~~
−
−	* Languages: C, C++, Assembly
−
−	* Platforms: All
−
−	~~==Required resources ==~~
−
−	~~Any~~
−
−	~~==Severity ==~~
−
−	~~Medium~~
−
−	~~==Likelihood of exploit ==~~
−
−	~~Medium~~
−
−	~~==Avoidance and mitigation ==~~
−
−	* Requirements specification: The choice could be made to use a language that is not susceptible to these issues.
−
−	* Implementation: ~~If all pointers that could have been modified are sanity-checked previous to use, nearly all null-pointer dereferences can be prevented.~~
−
−	~~==Discussion ==~~
−
−	Null-pointer dereferences, while common, can generally be found and corrected in a simply way. They will always result in the crash of the process - unless exception handling (on some platforms) in invoked, and even then, little can be done to salvage the process.
−
−	~~==Examples ==~~
−
−	Null-pointer dereference issue can occur through a number of flaws, including race conditions, and simple programming omissions. While there are no complete fixes aside from contentious programming, the following steps will go a long way to ensure that null-pointer dereferences do not occur.
−
−	~~Before using a pointer, ensure that it is not equal to NULL:~~
−
−	~~<pre>~~
−	~~if (pointer1 != NULL) {~~
−	/~~* make use of pointer1 *~~/
−	/* ... */
−	}
−	~~</pre>~~
−
−	~~When freeing pointers, ensure they are not set to NULL, and be sure to set them to NULL once they are freed:~~
−
−	~~<pre>~~
−	~~if (pointer1 != NULL) {~~
−	~~free(pointer1);~~
−	~~pointer1 = NULL;~~
−	}
−	</~~pre>~~
−
−	~~If you are working with a multi-threaded or otherwise asynchronous environment, ensure that proper locking APIs are used to lock before the if statement; and unlock when it has finished.~~
−
−	~~==Related problems ==~~
−
−	* [[Miscalculated null termination]]
−
−	* [[State synchronization error]]

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		+	#REDIRECT [[::Category:Vulnerability]]
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