linux-sg2042/arch/arm/kernel
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
..
.gitignore [ARM] 5194/1: update .gitignore 2008-08-12 19:54:09 +01:00
Makefile Merge branch 'devel-stable' into devel 2010-07-31 14:20:16 +01:00
armksyms.c ARM: unexport symbols used to implement floating point emulation 2009-12-15 16:28:22 +10:30
arthur.c [ARM] arm/kernel/arthur.c: add MODULE_LICENSE 2008-05-17 22:55:16 +01:00
asm-offsets.c ARM: stack protector: change the canary value per task 2010-06-14 21:31:01 -04:00
atags.c clean up atags exporting code 2008-05-30 10:33:49 +02:00
atags.h [ARM] 4736/1: Export atags to userspace and allow kexec to use customised atags 2008-02-04 13:21:03 +00:00
bios32.c ARM: 6058/1: Add support for PCI domains 2010-04-22 21:38:11 +01:00
calls.S ARM: 6343/1: wire up fanotify and prlimit64 syscalls on ARM 2010-09-01 10:06:08 +01:00
compat.c ARM: deprecate support for old way to pass kernel parameters 2010-07-07 16:38:36 +02:00
compat.h ARM: deprecate support for old way to pass kernel parameters 2010-07-07 16:38:36 +02:00
crash_dump.c ARM: 6120/1: kdump: implement copy_oldmem_page() 2010-07-09 15:00:53 +01:00
crunch-bits.S [ARM] Move include/asm-arm/arch-* to arch/arm/*/include/mach 2008-08-07 09:55:48 +01:00
crunch.c ARM: Convert VFP/Crunch/XscaleCP thread_release() to exit_thread() 2009-12-18 14:53:41 +00:00
debug.S ARM: 5910/1: ARM: Add tmp register for addruart and loadsp 2010-02-12 17:27:52 +00:00
dma-isa.c ARM: dma-isa: request cascade channel after registering it 2009-12-24 18:34:08 +00:00
dma.c ARM: dma: add /proc/dma support to arch/arm/kernel/dma.c 2010-04-14 13:13:30 +01:00
early_printk.c ARM: Add an earlyprintk debug console 2009-12-09 10:02:18 +00:00
ecard.c arm: struct device - replace bus_id with dev_name(), dev_set_name() 2009-01-06 10:44:43 -08:00
ecard.h [ARM] rpc: ecard: remove deprecated ecard_address() and relatives 2008-07-03 14:25:58 +01:00
elf.c ARM: 5883/1: Revert "disable NX support for OABI-supporting kernels" 2010-01-18 14:12:11 +00:00
entry-armv.S Merge branch 'devel-stable' into devel 2010-07-31 14:20:16 +01:00
entry-common.S arm: fix really nasty sigreturn bug 2010-09-17 10:22:18 -07:00
entry-header.S ARM: 5991/1: Fix regression in restore_user_regs macro 2010-03-15 17:20:08 +00:00
etm.c Input: sysrq - drop tty argument from sysrq ops handlers 2010-08-19 22:07:06 -07:00
fiq.c [ARM] 5421/1: ftrace: fix crash due to tracing of __naked functions 2009-03-12 21:33:03 +00:00
ftrace.c ARM: fix build error in arch/arm/kernel/process.c 2010-04-21 08:45:21 +01:00
head-common.S ARM: 5784/1: fix early boot machine ID mismatch error display 2009-11-08 11:58:54 +00:00
head-nommu.S ARM: convert to use __HEAD and HEAD_TEXT macros. 2009-11-23 20:33:34 +00:00
head.S ARM: convert to use __HEAD and HEAD_TEXT macros. 2009-11-23 20:33:34 +00:00
init_task.c Use new __init_task_data macro in arch init_task.c files. 2009-09-21 06:27:08 +02:00
io.c [ARM] Convert asm/io.h to linux/io.h 2008-09-06 12:10:45 +01:00
irq.c ARM: 6197/2: preliminary support for sparse IRQ 2010-07-09 14:41:33 +01:00
isa.c sysctl: Drop & in front of every proc_handler. 2009-11-18 08:37:40 -08:00
iwmmxt.S [ARM] 3707/1: iwmmxt: use the generic thread notifier infrastructure 2006-07-01 19:56:48 +01:00
kgdb.c ARM: 6326/1: kgdb: fix GDB_MAX_REGS no longer used 2010-08-14 09:28:35 +01:00
kprobes-decode.c ARM: 6226/1: fix kprobe bug in ldr instruction emulation 2010-07-14 23:28:06 +01:00
kprobes.c Merge branch 'master' into export-slabh 2010-04-05 11:37:28 +09:00
leds.c ARM: move LED support code out of arch/arm/kernel/time.c 2010-02-15 21:39:12 +00:00
machine_kexec.c Merge branch 'misc' into devel 2010-07-31 14:20:02 +01:00
module.c ARM: 6191/1: Do not compile the Thumb-2 module relocations on an ARM kernel 2010-08-05 10:35:48 +01:00
perf_event.c ARM: 6352/1: perf: fix event validation 2010-09-02 16:36:42 +01:00
pmu.c ARM: 6064/1: pmu: register IRQs at runtime 2010-05-17 11:53:57 +01:00
process.c Merge branch 'devel-stable' into devel 2010-07-31 14:20:16 +01:00
ptrace.c ARM: 6199/1: Add kprobe-based event tracer 2010-07-09 14:41:34 +01:00
ptrace.h arm: use generic ptrace_resume code 2010-03-12 15:52:38 -08:00
relocate_kernel.S ARM: 6119/1: kdump: skip indirection page when crashing 2010-07-09 15:00:52 +01:00
return_address.c [ARM] 5613/1: implement CALLER_ADDRESSx 2009-07-21 17:21:28 +01:00
setup.c Merge branch 'devel-stable' into devel 2010-07-31 14:20:16 +01:00
signal.c ARM: 6051/1: VFP: preserve the HW context when calling signal handlers 2010-04-14 11:11:30 +01:00
signal.h ARM: Fix signal restart issues with NX and OABI compat 2009-10-25 15:39:37 +00:00
smp.c ARM: call machine_shutdown() from machine_halt(), etc 2010-07-27 10:48:43 +01:00
smp_scu.c Check whether the SCU was already initialised 2009-11-05 10:10:36 +00:00
smp_twd.c ARM: SMP: Always enable clock event broadcast support 2010-07-27 10:48:42 +01:00
stacktrace.c [ARM] 5613/1: implement CALLER_ADDRESSx 2009-07-21 17:21:28 +01:00
sys_arm.c Make do_execve() take a const filename pointer 2010-08-17 18:07:43 -07:00
sys_oabi-compat.c Mark arguments to certain syscalls as being const 2010-08-13 16:53:13 -07:00
tcm.c ARM: 6225/1: make TCM allocation static and common for all archs 2010-07-27 10:42:38 +01:00
tcm.h ARM: 5580/2: ARM TCM (Tightly-Coupled Memory) support v3 2009-09-15 22:11:05 +01:00
thumbee.c Fix the teehbr_read function prototype 2008-11-10 14:14:11 +00:00
time.c ARM: convert arm to arch_gettimeoffset() 2010-03-24 08:08:58 +00:00
traps.c ARM: 6207/1: Replace CONFIG_HAS_TLS_REG with HWCAP_TLS and check for it on V6 2010-07-09 14:41:35 +01:00
unwind.c ARM: 6140/1: silence a bogus sparse warning in unwind.c 2010-05-24 20:42:03 +01:00
vmlinux.lds.S ARM: 5880/1: arm: use generic infrastructure for early params 2010-02-15 21:39:13 +00:00
xscale-cp0.c ARM: Convert VFP/Crunch/XscaleCP thread_release() to exit_thread() 2009-12-18 14:53:41 +00:00