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Date: Mon, 26 Jun 2017 14:04:01 -0700
From: Kees Cook <>
To: "" <>
Cc: LKML <>, 
	"" <>
Subject: non-x86 per-task stack canaries


The stack protector functionality on x86_64 uses %gs:0x28 (%gs is the
percpu area) for __stack_chk_guard, and all other architectures use a
global variable instead. This means we never change the stack canary
on non-x86 architectures which allows for a leak in one task to expose
the canary in another task.

I'm curious what thoughts people may have about how to get this
correctly implemented. Teaching the compiler about per-cpu data sounds
exciting. :)


Kees Cook
Pixel Security

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