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authorRusty Russell <rusty@rustcorp.com.au>2013-09-05 17:45:53 +0930
committerRusty Russell <rusty@rustcorp.com.au>2013-09-06 08:09:27 +0930
commit98fb4e5e6b100a247ce2dbf2d1699726fdcdef20 (patch)
treecaed1f9e084f2e8f7d1a38b8705d2c7831da2ee8 /drivers/lguest/interrupts_and_traps.c
parent4623c28e222d82f87537ef66db61ebcfbd8306db (diff)
lguest: fix guest kernel stack overflow when TF bit set.
The symptoms are that running gdb on a binary causes the guest to overflow the kernels stack (after some period of time), resulting in it finally being killed with a "Bad address" message. Reported-by: Sakari Ailus <sakari.ailus@iki.fi> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Diffstat (limited to 'drivers/lguest/interrupts_and_traps.c')
-rw-r--r--drivers/lguest/interrupts_and_traps.c10
1 files changed, 10 insertions, 0 deletions
diff --git a/drivers/lguest/interrupts_and_traps.c b/drivers/lguest/interrupts_and_traps.c
index 28433a155d6..70dfcdc29f1 100644
--- a/drivers/lguest/interrupts_and_traps.c
+++ b/drivers/lguest/interrupts_and_traps.c
@@ -140,6 +140,16 @@ static void set_guest_interrupt(struct lg_cpu *cpu, u32 lo, u32 hi,
cpu->regs->eip = idt_address(lo, hi);
/*
+ * Trapping always clears these flags:
+ * TF: Trap flag
+ * VM: Virtual 8086 mode
+ * RF: Resume
+ * NT: Nested task.
+ */
+ cpu->regs->eflags &=
+ ~(X86_EFLAGS_TF|X86_EFLAGS_VM|X86_EFLAGS_RF|X86_EFLAGS_NT);
+
+ /*
* There are two kinds of interrupt handlers: 0xE is an "interrupt
* gate" which expects interrupts to be disabled on entry.
*/