x86/pkeys: Make mprotect_key() mask off additional vm_flags (a8502b67) · Commits · 戴 / test

Today, mprotect() takes 4 bits of data: PROT_READ/WRITE/EXEC/NONE. Three of those bits: READ/WRITE/EXEC get translated directly in to vma->vm_flags by calc_vm_prot_bits(). If a bit is unset in mprotect()'s 'prot' argument then it must be cleared in vma->vm_flags during the mprotect() call. We do this clearing today by first calculating the VMA flags we want set, then clearing the ones we do not want to inherit from the original VMA: vm_flags = calc_vm_prot_bits(prot, key); ... newflags = vm_flags; newflags |= (vma->vm_flags & ~(VM_READ | VM_WRITE | VM_EXEC)); However, we *also* want to mask off the original VMA's vm_flags in which we store the protection key. To do that, this patch adds a new macro: ARCH_VM_PKEY_FLAGS which allows the architecture to specify additional bits that it would like cleared. We use that to ensure that the VM_PKEY_BIT* bits get cleared. Signed-off-by:

Dave Hansen <dave.hansen@linux.intel.com> Acked-by:

Mel Gorman <mgorman@techsingularity.net> Reviewed-by:

Thomas Gleixner <tglx@linutronix.de> Cc: linux-arch@vger.kernel.org Cc: Dave Hansen <dave@sr71.net> Cc: arnd@arndb.de Cc: linux-api@vger.kernel.org Cc: linux-mm@kvack.org Cc: luto@kernel.org Cc: akpm@linux-foundation.org Cc: torvalds@linux-foundation.org Link: http://lkml.kernel.org/r/20160729163013.E48D6981@viggo.jf.intel.com Signed-off-by:

Thomas Gleixner <tglx@linutronix.de>

arch/x86/include/asm/pkeys.h

+2 −0

Original line number	Diff line number	Diff line
		@@ -38,4 +38,6 @@ static inline int arch_override_mprotect_pkey(struct vm_area_struct *vma,
		extern int __arch_set_user_pkey_access(struct task_struct *tsk, int pkey,
		unsigned long init_val);

		#define ARCH_VM_PKEY_FLAGS (VM_PKEY_BIT0 \| VM_PKEY_BIT1 \| VM_PKEY_BIT2 \| VM_PKEY_BIT3)

		#endif /_ASM_X86_PKEYS_H /

include/linux/pkeys.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -16,6 +16,7 @@
		#define execute_only_pkey(mm) (0)
		#define arch_override_mprotect_pkey(vma, prot, pkey) (0)
		#define PKEY_DEDICATED_EXECUTE_ONLY 0
		#define ARCH_VM_PKEY_FLAGS 0
		#endif /* ! CONFIG_ARCH_HAS_PKEYS */

		#endif /* _LINUX_PKEYS_H */

mm/mprotect.c

+10 −1

Original line number	Diff line number	Diff line
		@@ -417,6 +417,7 @@ static int do_mprotect_pkey(unsigned long start, size_t len,
		prev = vma;

		for (nstart = start ; ; ) {
		unsigned long mask_off_old_flags;
		unsigned long newflags;
		int new_vma_pkey;

		@@ -426,9 +427,17 @@ static int do_mprotect_pkey(unsigned long start, size_t len,
		if (rier && (vma->vm_flags & VM_MAYEXEC))
		prot \|= PROT_EXEC;

		/*
		* Each mprotect() call explicitly passes r/w/x permissions.
		* If a permission is not passed to mprotect(), it must be
		* cleared from the VMA.
		*/
		mask_off_old_flags = VM_READ \| VM_WRITE \| VM_EXEC \|
		ARCH_VM_PKEY_FLAGS;

		new_vma_pkey = arch_override_mprotect_pkey(vma, prot, pkey);
		newflags = calc_vm_prot_bits(prot, new_vma_pkey);
		newflags \|= (vma->vm_flags & ~(VM_READ \| VM_WRITE \| VM_EXEC));
		newflags \|= (vma->vm_flags & ~mask_off_old_flags);

		/* newflags >> 4 shift VM_MAY% in place of VM_% */
		if ((newflags & ~(newflags >> 4)) & (VM_READ \| VM_WRITE \| VM_EXEC)) {

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