From ec2c1fcefb200c6cb7e09553f3c6af8815013d83 Mon Sep 17 00:00:00 2001 From: Florian Weimer Date: Wed, 30 Aug 2017 16:39:41 +0200 Subject: malloc: Abort on heap corruption, without a backtrace [BZ #21754] The stack trace printing caused deadlocks and has been itself been targeted by code execution exploits. --- manual/tunables.texi | 28 +++++++--------------------- 1 file changed, 7 insertions(+), 21 deletions(-) (limited to 'manual/tunables.texi') diff --git a/manual/tunables.texi b/manual/tunables.texi index 3c19567..b09e3fe 100644 --- a/manual/tunables.texi +++ b/manual/tunables.texi @@ -71,27 +71,13 @@ following tunables in the @code{malloc} namespace: This tunable supersedes the @env{MALLOC_CHECK_} environment variable and is identical in features. -Setting this tunable enables a special (less efficient) memory allocator for -the malloc family of functions that is designed to be tolerant against simple -errors such as double calls of free with the same argument, or overruns of a -single byte (off-by-one bugs). Not all such errors can be protected against, -however, and memory leaks can result. The following list describes the values -that this tunable can take and the effect they have on malloc functionality: - -@itemize @bullet -@item @code{0} Ignore all errors. The default allocator continues to be in -use, but all errors are silently ignored. -@item @code{1} Report errors. The alternate allocator is selected and heap -corruption, if detected, is reported as diagnostic messages to @code{stderr} -and the program continues execution. -@item @code{2} Abort on errors. The alternate allocator is selected and if -heap corruption is detected, the program is ended immediately by calling -@code{abort}. -@item @code{3} Fully enabled. The alternate allocator is selected and is fully -functional. That is, if heap corruption is detected, a verbose diagnostic -message is printed to @code{stderr} and the program is ended by calling -@code{abort}. -@end itemize +Setting this tunable to a non-zero value enables a special (less +efficient) memory allocator for the malloc family of functions that is +designed to be tolerant against simple errors such as double calls of +free with the same argument, or overruns of a single byte (off-by-one +bugs). Not all such errors can be protected against, however, and memory +leaks can result. Any detected heap corruption results in immediate +termination of the process. Like @env{MALLOC_CHECK_}, @code{glibc.malloc.check} has a problem in that it diverges from normal program behavior by writing to @code{stderr}, which could -- cgit v1.1