The problem with a non-executable stack is that there are legitimate uses for executing code on the stack - among these are signal handlers in the Linux kernel and the use of "trampolines" to facilitate the use of nested functions (an extension of the C language) by GCC. To deal with this problem, the Openwall patch allows users the option of emulating trampolines (in most cases, this shouldn't cause much extra overhead). The emulation of trampolines is made available as a separate option: if you enable it, the chances of the emulation being tricked by an exploit are greater, if you don't enable it, you run the risk of some your applications breaking (test it!)
[^] # Re: Quels sont les défauts ?
Posté par Xavier Poinsard . En réponse à la dépêche Le patch OpenWall. Évalué à 6.
The problem with a non-executable stack is that there are legitimate uses for executing code on the stack - among these are signal handlers in the Linux kernel and the use of "trampolines" to facilitate the use of nested functions (an extension of the C language) by GCC. To deal with this problem, the Openwall patch allows users the option of emulating trampolines (in most cases, this shouldn't cause much extra overhead). The emulation of trampolines is made available as a separate option: if you enable it, the chances of the emulation being tricked by an exploit are greater, if you don't enable it, you run the risk of some your applications breaking (test it!)