Commit 880a98c3 authored Nov 21, 2019 by Thomas Gleixner Committed by Peter Zijlstra Nov 21, 2019

x86/cpu_entry_area: Add guard page for entry stack on 32bit



The entry stack in the cpu entry area is protected against overflow by the
readonly GDT on 64-bit, but on 32-bit the GDT needs to be writeable and
therefore does not trigger a fault on stack overflow.

Add a guard page.

Fixes: c482feef ("x86/entry/64: Make cpu_entry_area.tss read-only")
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: stable@kernel.org

parent f490e07c

arch/x86/include/asm/cpu_entry_area.h

+5 −1

Original line number	Diff line number	Diff line
		@@ -78,8 +78,12 @@ struct cpu_entry_area {

		/*
		* The GDT is just below entry_stack and thus serves (on x86_64) as
		* a a read-only guard page.
		* a read-only guard page. On 32-bit the GDT must be writeable, so
		* it needs an extra guard page.
		*/
		#ifdef CONFIG_X86_32
		char guard_entry_stack[PAGE_SIZE];
		#endif
		struct entry_stack_page entry_stack_page;

		/*

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