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Commit 98fb4e5e authored by Rusty Russell's avatar Rusty Russell
Browse files

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: default avatarSakari Ailus <sakari.ailus@iki.fi>
Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
parent 4623c28e

drivers/lguest/interrupts_and_traps.c

+10 −0
Original line number Diff line number Diff line
@@ -139,6 +139,16 @@ static void set_guest_interrupt(struct lg_cpu *cpu, u32 lo, u32 hi, 
	cpu->regs->cs = (__KERNEL_CS|GUEST_PL);

	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.