lguest: fix sense if IF flag on interrupt injection
The sense of the IF bit is backwards in the host interrupt handling.
This means we always save "IF=1" on the stack when injecting an
interrupt. It turns out this is almost always correct (unless the
guest is taking a page fault in an interrupt due to an unpopulated
vmalloc mapping), so went unnoticed.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/drivers/lguest/interrupts_and_traps.c b/drivers/lguest/interrupts_and_traps.c
index d9de5bb..bee029b 100644
--- a/drivers/lguest/interrupts_and_traps.c
+++ b/drivers/lguest/interrupts_and_traps.c
@@ -38,12 +38,12 @@
ss = lg->regs->ss;
}
- /* We use IF bit in eflags to indicate whether irqs were disabled
- (it's always 0, since irqs are enabled when guest is running). */
+ /* We use IF bit in eflags to indicate whether irqs were enabled
+ (it's always 1, since irqs are enabled when guest is running). */
eflags = lg->regs->eflags;
- if (get_user(irq_enable, &lg->lguest_data->irq_enabled))
- irq_enable = 0;
- eflags |= (irq_enable & X86_EFLAGS_IF);
+ if (get_user(irq_enable, &lg->lguest_data->irq_enabled) == 0
+ && !(irq_enable & X86_EFLAGS_IF))
+ eflags &= ~X86_EFLAGS_IF;
push_guest_stack(lg, &gstack, eflags);
push_guest_stack(lg, &gstack, lg->regs->cs);