linux/arch
Al Viro 653d48b221 arm: fix really nasty sigreturn bug
If a signal hits us outside of a syscall and another gets delivered
when we are in sigreturn (e.g. because it had been in sa_mask for
the first one and got sent to us while we'd been in the first handler),
we have a chance of returning from the second handler to location one
insn prior to where we ought to return.  If r0 happens to contain -513
(-ERESTARTNOINTR), sigreturn will get confused into doing restart
syscall song and dance.

Incredible joy to debug, since it manifests as random, infrequent and
very hard to reproduce double execution of instructions in userland
code...

The fix is simple - mark it "don't bother with restarts" in wrapper,
i.e. set r8 to 0 in sys_sigreturn and sys_rt_sigreturn wrappers,
suppressing the syscall restart handling on return from these guys.
They can't legitimately return a restart-worthy error anyway.

Testcase:
	#include <unistd.h>
	#include <signal.h>
	#include <stdlib.h>
	#include <sys/time.h>
	#include <errno.h>

	void f(int n)
	{
		__asm__ __volatile__(
			"ldr r0, [%0]\n"
			"b 1f\n"
			"b 2f\n"
			"1:b .\n"
			"2:\n" : : "r"(&n));
	}

	void handler1(int sig) { }
	void handler2(int sig) { raise(1); }
	void handler3(int sig) { exit(0); }

	main()
	{
		struct sigaction s = {.sa_handler = handler2};
		struct itimerval t1 = { .it_value = {1} };
		struct itimerval t2 = { .it_value = {2} };

		signal(1, handler1);

		sigemptyset(&s.sa_mask);
		sigaddset(&s.sa_mask, 1);
		sigaction(SIGALRM, &s, NULL);

		signal(SIGVTALRM, handler3);

		setitimer(ITIMER_REAL, &t1, NULL);
		setitimer(ITIMER_VIRTUAL, &t2, NULL);

		f(-513); /* -ERESTARTNOINTR */

		write(1, "buggered\n", 9);
		return 1;
	}

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Acked-by: Russell King <rmk+kernel@arm.linux.org.uk>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2010-09-17 10:22:18 -07:00
..
alpha alpha: Fix printk format errors 2010-09-01 11:25:17 -04:00
arm arm: fix really nasty sigreturn bug 2010-09-17 10:22:18 -07:00
avr32 Make do_execve() take a const filename pointer 2010-08-17 18:07:43 -07:00
blackfin Blackfin: bf52x/bf54x boards: drop unused nand page size 2010-08-27 16:08:43 -04:00
cris Make do_execve() take a const filename pointer 2010-08-17 18:07:43 -07:00
frv Make do_execve() take a const filename pointer 2010-08-17 18:07:43 -07:00
h8300 h8300: Fix missing consts in kernel_execve() 2010-09-07 13:52:28 -07:00
ia64 Merge branch 'release' of git://git.kernel.org/pub/scm/linux/kernel/git/aegl/linux-2.6 2010-09-16 12:58:44 -07:00
m32r Make do_execve() take a const filename pointer 2010-08-17 18:07:43 -07:00
m68k m68k,m68knommu: Wire up fanotify_init, fanotify_mark, and prlimit64 2010-09-13 20:28:45 +02:00
m68knommu m68k,m68knommu: Wire up fanotify_init, fanotify_mark, and prlimit64 2010-09-13 20:28:45 +02:00
microblaze Merge branch 'merge-devicetree' of git://git.secretlab.ca/git/linux-2.6 2010-08-18 09:26:17 -07:00
mips compat: Make compat_alloc_user_space() incorporate the access_ok() 2010-09-14 16:08:45 -07:00
mn10300 MN10300: Fix up the IRQ names for the on-chip serial ports 2010-09-14 17:06:28 -07:00
parisc compat: Make compat_alloc_user_space() incorporate the access_ok() 2010-09-14 16:08:45 -07:00
powerpc compat: Make compat_alloc_user_space() incorporate the access_ok() 2010-09-14 16:08:45 -07:00
s390 compat: Make compat_alloc_user_space() incorporate the access_ok() 2010-09-14 16:08:45 -07:00
score Make do_execve() take a const filename pointer 2010-08-17 18:07:43 -07:00
sh Make do_execve() take a const filename pointer 2010-08-17 18:07:43 -07:00
sparc compat: Make compat_alloc_user_space() incorporate the access_ok() 2010-09-14 16:08:45 -07:00
tile Merge branch 'stable' of git://git.kernel.org/pub/scm/linux/kernel/git/cmetcalf/linux-tile 2010-09-16 12:54:54 -07:00
um Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/dtor/input 2010-08-28 13:55:31 -07:00
x86 Merge branch 'x86-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2010-09-16 19:38:08 -07:00
xtensa Make do_execve() take a const filename pointer 2010-08-17 18:07:43 -07:00
.gitignore
Kconfig Merge branch 'perf/nmi' into perf/core 2010-08-05 08:45:05 +02:00