From 508a92741a105e2e3d466cd727fb73154ebf08de Mon Sep 17 00:00:00 2001 From: Jeff Dike Date: Tue, 18 Sep 2007 22:46:49 -0700 Subject: 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 Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- arch/um/os-Linux/signal.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'arch/um/os-Linux/signal.c') diff --git a/arch/um/os-Linux/signal.c b/arch/um/os-Linux/signal.c index 18e5c8b67eb8..b98f7ea2d2f6 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); if(bail) return; -- cgit v1.2.3-59-g8ed1b