ARC: [mm] Make stack/heap Non-executable by default (3abc9448) · Commits · 戴 / test

1. For VM_EXEC based delayed dcache/icache flush, reduces the number of flushes. 2. Makes this security feature ON by default rather than OFF before. 3. Applications can use mprotect() to selectively override this. 4. ELF binaries have a GNU_STACK segment which can easily override the kernel default permissions. For nested-functions/trampolines, gcc already auto-enables executable stack in elf. Others needing this can use -Wl,-z,execstack option. Signed-off-by:

Vineet Gupta <vgupta@synopsys.com>

arch/arc/Kconfig

+0 −7

Original line number	Diff line number	Diff line
		@@ -362,13 +362,6 @@ config ARC_MISALIGN_ACCESS
		Use ONLY-IF-ABS-NECESSARY as it will be very slow and also can hide
		potential bugs in code

		config ARC_STACK_NONEXEC
		bool "Make stack non-executable"
		default n
		help
		To disable the execute permissions of stack/heap of processes
		which are enabled by default.

		config HZ
		int "Timer Frequency"
		default 100

arch/arc/include/asm/page.h

+1 −6

Original line number	Diff line number	Diff line
		@@ -96,13 +96,8 @@ typedef unsigned long pgtable_t;

		#define virt_addr_valid(kaddr) pfn_valid(__pa(kaddr) >> PAGE_SHIFT)

		/* Default Permissions for page, used in mmap.c */
		#ifdef CONFIG_ARC_STACK_NONEXEC
		/* Default Permissions for stack/heaps pages (Non Executable) */
		#define VM_DATA_DEFAULT_FLAGS (VM_READ \| VM_WRITE \| VM_MAYREAD \| VM_MAYWRITE)
		#else
		#define VM_DATA_DEFAULT_FLAGS (VM_READ \| VM_WRITE \| VM_EXEC \| \
		VM_MAYREAD \| VM_MAYWRITE \| VM_MAYEXEC)
		#endif

		#define WANT_PAGE_VIRTUAL 1

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