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x86/irq/64: Limit IST stack overflow check to #DB stack

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[ Upstream commit 7dbcf2b0b770eeb803a416ee8dcbef78e6389d40 ]

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  37fe6a42b343 ("x86: Check stack overflow in detail")

added a broad check for the full exception stack area, i.e. it considers
the full exception stack area as valid.

That's wrong in two aspects:

 1) It does not check the individual areas one by one

 2) #DF, NMI and #MCE are not enabling interrupts which means that a
    regular device interrupt cannot happen in their context. In fact if a
    device interrupt hits one of those IST stacks that's a bug because some
    code path enabled interrupts while handling the exception.

Limit the check to the #DB stack and consider all other IST stacks as
'overflow' or invalid.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Mitsuo Hayasaka <mitsuo.hayasaka.hu@hitachi.com>
Cc: Nicolai Stange <nstange@suse.de>
Cc: Sean Christopherson <sean.j.christopherson@intel.com>
Cc: x86-ml <x86@kernel.org>
Link: https://lkml.kernel.org/r/20190414160143.682135110@linutronix.de
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Thomas Gleixner 2019-04-14 17:59:38 +02:00 committed by Greg Kroah-Hartman
parent 46f9a77b35
commit dc81cfb3cc
1 changed files with 14 additions and 5 deletions
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19
arch/x86/kernel/irq_64.c
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@ -26,9 +26,18 @@ int sysctl_panic_on_stackoverflow;
/*
* Probabilistic stack overflow check:
*
* Only check the stack in process context, because everything else
* runs on the big interrupt stacks. Checking reliably is too expensive,
* so we just check from interrupts.
* Regular device interrupts can enter on the following stacks:
*
* - User stack
*
* - Kernel task stack
*
* - Interrupt stack if a device driver reenables interrupts
* which should only happen in really old drivers.
*
* - Debug IST stack
*
* All other contexts are invalid.
*/
static inline void stack_overflow_check(struct pt_regs *regs)
{
@ -53,8 +62,8 @@ static inline void stack_overflow_check(struct pt_regs *regs)
return;
oist = this_cpu_ptr(&orig_ist);
estack_top = (u64)oist->ist[0] - EXCEPTION_STKSZ + STACK_TOP_MARGIN;
estack_bottom = (u64)oist->ist[N_EXCEPTION_STACKS - 1];
estack_bottom = (u64)oist->ist[DEBUG_STACK];
estack_top = estack_bottom - DEBUG_STKSZ + STACK_TOP_MARGIN;
if (regs->sp >= estack_top && regs->sp <= estack_bottom)
return;