Messages in this thread | | | Date | Wed, 4 May 2022 12:07:57 -0700 | From | Kees Cook <> | Subject | Re: [PATCH v2 09/13] lkdtm/stackleak: rework boundary management |
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On Wed, Apr 27, 2022 at 06:31:24PM +0100, Mark Rutland wrote: > There are a few problems with the way the LKDTM STACKLEAK_ERASING test > manipulates the stack pointer and boundary values: > > * It uses the address of a local variable to determine the current stack > pointer, rather than using current_stack_pointer directly. As the > local variable could be placed anywhere within the stack frame, this > can be an over-estimate of the true stack pointer value. > > * Is uses an estiamte of the current stack pointer as the upper boundary > when scanning for poison, even though prior functions could have used > more stack (and may have updated current->lowest stack accordingly). > > * A pr_info() call is made in the middle of the test. As the printk() > code is out-of-line and will make use of the stack, this could clobber > poison and/or adjust current->lowest_stack. It would be better to log > the metadata after the body of the test to avoid such problems.
Yeah, I noticed this too when I was testing the v1 series. I started cleaning it up, but your version is much better. :)
-- Kees Cook
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