MIPS: non-exec stack & heap when non-exec PT_GNU_STACK is present (1a770b85) · Commits · 戴 / test

The stack and heap have both been executable by default on MIPS until now. This patch changes the default to be non-executable, but only for ELF binaries with a non-executable PT_GNU_STACK header present. This does apply to both the heap & the stack, despite the name PT_GNU_STACK, and this matches the behaviour of other architectures like ARM & x86. Current MIPS toolchains do not produce the PT_GNU_STACK header, which means that we can rely upon this patch not changing the behaviour of existing binaries. The new default will only take effect for newly compiled binaries once toolchains are updated to support PT_GNU_STACK, and since those binaries are newly compiled they can be compiled expecting the change in default behaviour. Again this matches the way in which the ARM & x86 architectures handled their implementations of non-executable memory. Signed-off-by:

Paul Burton <paul.burton@imgtec.com> Cc: Leonid Yegoshin <leonid.yegoshin@imgtec.com> Cc: Maciej Rozycki <maciej.rozycki@imgtec.com> Cc: Faraz Shahbazker <faraz.shahbazker@imgtec.com> Cc: Raghu Gandham <raghu.gandham@imgtec.com> Cc: Matthew Fortune <matthew.fortune@imgtec.com> Cc: linux-mips@linux-mips.org Patchwork: https://patchwork.linux-mips.org/patch/13765/ Signed-off-by:

Ralf Baechle <ralf@linux-mips.org>

arch/mips/include/asm/elf.h

+3 −0

Original line number	Diff line number	Diff line
		@@ -499,4 +499,7 @@ extern int arch_check_elf(void ehdr, bool has_interpreter, void interp_ehdr,
		extern void mips_set_personality_nan(struct arch_elf_state *state);
		extern void mips_set_personality_fp(struct arch_elf_state *state);

		#define elf_read_implies_exec(ex, stk) mips_elf_read_implies_exec(&(ex), stk)
		extern int mips_elf_read_implies_exec(void *elf_ex, int exstack);

		#endif /* _ASM_ELF_H */

arch/mips/include/asm/page.h

+4 −2

Original line number	Diff line number	Diff line
		@@ -229,7 +229,9 @@ extern int __virt_addr_valid(const volatile void *kaddr);
		#define virt_addr_valid(kaddr) \
		__virt_addr_valid((const volatile void *) (kaddr))

		#define VM_DATA_DEFAULT_FLAGS (VM_READ \| VM_WRITE \| VM_EXEC \| \
		#define VM_DATA_DEFAULT_FLAGS \
		(VM_READ \| VM_WRITE \| \
		((current->personality & READ_IMPLIES_EXEC) ? VM_EXEC : 0) \| \
		VM_MAYREAD \| VM_MAYWRITE \| VM_MAYEXEC)

		#define UNCAC_ADDR(addr) ((addr) - PAGE_OFFSET + UNCAC_BASE)

arch/mips/kernel/elf.c

+19 −0

Original line number	Diff line number	Diff line
		@@ -8,9 +8,12 @@
		* option) any later version.
		*/

		#include <linux/binfmts.h>
		#include <linux/elf.h>
		#include <linux/export.h>
		#include <linux/sched.h>

		#include <asm/cpu-features.h>
		#include <asm/cpu-info.h>

		/* Whether to accept legacy-NaN and 2008-NaN user binaries. */
		@@ -326,3 +329,19 @@ void mips_set_personality_nan(struct arch_elf_state *state)
		BUG();
		}
		}

		int mips_elf_read_implies_exec(void *elf_ex, int exstack)
		{
		if (exstack != EXSTACK_DISABLE_X) {
		/* The binary doesn't request a non-executable stack */
		return 1;
		}

		if (!cpu_has_rixi) {
		/* The CPU doesn't support non-executable memory */
		return 1;
		}

		return 0;
		}
		EXPORT_SYMBOL(mips_elf_read_implies_exec);

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