Linus Torvalds 33692f2759 vm: add VM_FAULT_SIGSEGV handling support ... The core VM already knows about VM_FAULT_SIGBUS, but cannot return a "you should SIGSEGV" error, because the SIGSEGV case was generally handled by the caller - usually the architecture fault handler. That results in lots of duplication - all the architecture fault handlers end up doing very similar "look up vma, check permissions, do retries etc" - but it generally works. However, there are cases where the VM actually wants to SIGSEGV, and applications _expect_ SIGSEGV. In particular, when accessing the stack guard page, libsigsegv expects a SIGSEGV. And it usually got one, because the stack growth is handled by that duplicated architecture fault handler. However, when the generic VM layer started propagating the error return from the stack expansion in commit fee7e49d45 ("mm: propagate error from stack expansion even for guard page"), that now exposed the existing VM_FAULT_SIGBUS result to user space. And user space really expected SIGSEGV, not SIGBUS. To fix that case, we need to add a VM_FAULT_SIGSEGV, and teach all those duplicate architecture fault handlers about it. They all already have the code to handle SIGSEGV, so it's about just tying that new return value to the existing code, but it's all a bit annoying. This is the mindless minimal patch to do this. A more extensive patch would be to try to gather up the mostly shared fault handling logic into one generic helper routine, and long-term we really should do that cleanup. Just from this patch, you can generally see that most architectures just copied (directly or indirectly) the old x86 way of doing things, but in the meantime that original x86 model has been improved to hold the VM semaphore for shorter times etc and to handle VM_FAULT_RETRY and other "newer" things, so it would be a good idea to bring all those improvements to the generic case and teach other architectures about them too. Reported-and-tested-by: Takashi Iwai <tiwai@suse.de> Tested-by: Jan Engelhardt <jengelh@inai.de> Acked-by: Heiko Carstens <heiko.carstens@de.ibm.com> # "s390 still compiles and boots" Cc: linux-arch@vger.kernel.org Cc: stable@vger.kernel.org Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>		2015-01-29 10:51:32 -08:00
..
configs	arch/um: make it work with defconfig and x86_64	2013-11-17 11:31:48 +01:00
drivers	uml: Fix unsafe pid reference to foreground process group	2014-11-05 16:26:13 -08:00
include	Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next	2014-12-11 14:27:06 -08:00
kernel	vm: add VM_FAULT_SIGSEGV handling support	2015-01-29 10:51:32 -08:00
os-Linux	Revert "um: Fix wait_stub_done() error handling"	2014-07-20 12:56:34 +02:00
scripts	um: Preinclude include/linux/kern_levels.h	2012-09-27 20:20:09 +02:00
sys-ia64	uml: remove useless comments	2009-04-01 08:59:17 -07:00
sys-ppc	dump_stack: unify debug information printed by show_regs()	2013-04-30 17:04:02 -07:00
.gitignore	um: tell git to ignore generated files	2010-03-06 11:26:28 -08:00
Kconfig.char	um: remove used STDIO_CONSOLE Kconfig param	2013-11-17 11:32:27 +01:00
Kconfig.common	um: Skip futex_atomic_cmpxchg_inatomic() test	2015-01-04 14:20:26 +01:00
Kconfig.debug	lib: consolidate DEBUG_STACK_USAGE option	2011-05-25 08:39:54 -07:00
Kconfig.net	arch/um: remove depends on CONFIG_EXPERIMENTAL	2013-01-11 11:38:04 -08:00
Kconfig.rest	um: switch to use of drivers/Kconfig	2011-11-02 14:15:41 +01:00
Kconfig.um	arch/um: remove depends on CONFIG_EXPERIMENTAL	2013-01-11 11:38:04 -08:00
Makefile	um: Fix for relative objtree when generating x86 headers	2014-06-05 17:55:48 +02:00
Makefile-ia64
Makefile-os-Linux	x86, um: get rid of arch/um/os symlink	2008-10-22 22:55:22 -07:00
Makefile-ppc
Makefile-skas