Page MenuHomeFreeBSD

KASAN: Disable the sanitizer in stack_capture()
ClosedPublic

Authored by markj on May 5 2021, 2:44 PM.

Details

Summary

When unwinding the stack we may descend into a poisoned region of the
kernel stack. I don't see a good way to handle this except to disable
the sanitizer entirely.

Define __nosanitizeaddress depending on whether we're in the kernel or
not, since KASAN and ASAN require different attributes. Add
__nosanitizememory while I'm here.

A further complication is that clang raises an error if
no_sanitize("kernel-address") is applied to a global variable rather
than a function:

error: 'no_sanitize' attribute only applies to functions and methods

So, modify linker_set.h to apply the attribute only if we're not in the
kernel.

Diff Detail

Repository
rG FreeBSD src repository
Lint
Automatic diff as part of commit; lint not applicable.
Unit
Automatic diff as part of commit; unit tests not applicable.

Event Timeline

markj requested review of this revision.May 5 2021, 2:44 PM
sys/x86/x86/stack_machdep.c
73 ↗(On Diff #88683)

I have no idea what is going on there, but don't all called functions require the same handling, e.g. stack_zero? Is it happen to work because struct stack itself is 'not poisoned'?

sys/x86/x86/stack_machdep.c
73 ↗(On Diff #88683)

stack_zero() is fine, it's the inline dereference of the frame pointer that potentially causes problems.

Mostly on principle "I do not see anything wrong"

This revision is now accepted and ready to land.May 5 2021, 8:02 PM