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

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 <[email protected]>
Signed-off-by: Borislav Petkov <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Josh Poimboeuf <[email protected]>
Cc: Mitsuo Hayasaka <[email protected]>
Cc: Nicolai Stange <[email protected]>
Cc: Sean Christopherson <[email protected]>
Cc: x86-ml <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]

0 files changed, 0 insertions, 0 deletions