| From 1d8f6de114fb2dbc96173e033cb12fb125dcdfb8 Mon Sep 17 00:00:00 2001 |
| From: Thomas Gleixner <tglx@linutronix.de> |
| Date: Sun, 14 Apr 2019 17:59:38 +0200 |
| Subject: x86/irq/64: Limit IST stack overflow check to #DB stack |
| |
| [ Upstream commit 7dbcf2b0b770eeb803a416ee8dcbef78e6389d40 ] |
| |
| Commit |
| |
| 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> |
| --- |
| arch/x86/kernel/irq_64.c | 19 ++++++++++++++----- |
| 1 file changed, 14 insertions(+), 5 deletions(-) |
| |
| diff --git a/arch/x86/kernel/irq_64.c b/arch/x86/kernel/irq_64.c |
| index 0469cd078db15..b50ac9c7397bb 100644 |
| --- a/arch/x86/kernel/irq_64.c |
| +++ b/arch/x86/kernel/irq_64.c |
| @@ -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; |
| |
| -- |
| 2.20.1 |
| |