diff options
authorJeff Dike <jdike@addtoit.com>2007-09-18 22:46:49 -0700
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-09-19 11:24:18 -0700
commit508a92741a105e2e3d466cd727fb73154ebf08de (patch)
parent480eccf9ae1073b87bb4fe118971fbf134a5bc61 (diff)
uml: fix irqstack crash
This patch fixes a crash caused by an interrupt coming in when an IRQ stack is being torn down. When this happens, handle_signal will loop, setting up the IRQ stack again because the tearing down had finished, and handling whatever signals had come in. However, to_irq_stack returns a mask of pending signals to be handled, plus bit zero is set if the IRQ stack was already active, and thus shouldn't be torn down. This causes a problem because when handle_signal goes around the loop, sig will be zero, and to_irq_stack will duly set bit zero in the returned mask, faking handle_signal into believing that it shouldn't tear down the IRQ stack and return thread_info pointers back to their original values. This will eventually cause a crash, as the IRQ stack thread_info will continue pointing to the original task_struct and an interrupt will look into it after it has been freed. The fix is to stop passing a signal number into to_irq_stack. Rather, the pending signals mask is initialized beforehand with the bit for sig already set. References to sig in to_irq_stack can be replaced with references to the mask. [akpm@linux-foundation.org: use UL] Signed-off-by: Jeff Dike <jdike@linux.intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
3 files changed, 7 insertions, 6 deletions
diff --git a/arch/um/include/kern_util.h b/arch/um/include/kern_util.h
index 8d7f7c1cb9c..6c2be26f1d7 100644
--- a/arch/um/include/kern_util.h
+++ b/arch/um/include/kern_util.h
@@ -117,7 +117,7 @@ extern void sigio_handler(int sig, union uml_pt_regs *regs);
extern void copy_sc(union uml_pt_regs *regs, void *from);
-unsigned long to_irq_stack(int sig, unsigned long *mask_out);
+extern unsigned long to_irq_stack(unsigned long *mask_out);
unsigned long from_irq_stack(int nested);
diff --git a/arch/um/kernel/irq.c b/arch/um/kernel/irq.c
index 9870febdbea..cf0dd9cf8c4 100644
--- a/arch/um/kernel/irq.c
+++ b/arch/um/kernel/irq.c
@@ -518,13 +518,13 @@ int init_aio_irq(int irq, char *name, irq_handler_t handler)
static unsigned long pending_mask;
-unsigned long to_irq_stack(int sig, unsigned long *mask_out)
+unsigned long to_irq_stack(unsigned long *mask_out)
struct thread_info *ti;
unsigned long mask, old;
int nested;
- mask = xchg(&pending_mask, 1 << sig);
+ mask = xchg(&pending_mask, *mask_out);
if(mask != 0){
/* If any interrupts come in at this point, we want to
* make sure that their bits aren't lost by our
@@ -534,7 +534,7 @@ unsigned long to_irq_stack(int sig, unsigned long *mask_out)
* and pending_mask contains a bit for each interrupt
* that came in.
- old = 1 << sig;
+ old = *mask_out;
do {
old |= mask;
mask = xchg(&pending_mask, old);
@@ -550,6 +550,7 @@ unsigned long to_irq_stack(int sig, unsigned long *mask_out)
task = cpu_tasks[ti->cpu].task;
tti = task_thread_info(task);
*ti = *tti;
ti->real_thread = tti;
task->stack = ti;
diff --git a/arch/um/os-Linux/signal.c b/arch/um/os-Linux/signal.c
index 18e5c8b67eb..b98f7ea2d2f 100644
--- a/arch/um/os-Linux/signal.c
+++ b/arch/um/os-Linux/signal.c
@@ -119,7 +119,7 @@ void (*handlers[_NSIG])(int sig, struct sigcontext *sc);
void handle_signal(int sig, struct sigcontext *sc)
- unsigned long pending = 0;
+ unsigned long pending = 1UL << sig;
do {
int nested, bail;
@@ -134,7 +134,7 @@ void handle_signal(int sig, struct sigcontext *sc)
* have to return, and the upper handler will deal
* with this interrupt.
- bail = to_irq_stack(sig, &pending);
+ bail = to_irq_stack(&pending);