mm: make stack guard page logic use vm_prev pointer (0e8e50e2) · Commits · 戴 / test

Like the mlock() change previously, this makes the stack guard check code use vma->vm_prev to see what the mapping below the current stack is, rather than have to look it up with find_vma(). Also, accept an abutting stack segment, since that happens naturally if you split the stack with mlock or mprotect. Tested-by:

Ian Campbell <ijc@hellion.org.uk> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

mm/memory.c

+11 −4

Original line number	Diff line number	Diff line
		@@ -2770,11 +2770,18 @@ static inline int check_stack_guard_page(struct vm_area_struct *vma, unsigned lo
		{
		address &= PAGE_MASK;
		if ((vma->vm_flags & VM_GROWSDOWN) && address == vma->vm_start) {
		address -= PAGE_SIZE;
		if (find_vma(vma->vm_mm, address) != vma)
		return -ENOMEM;
		struct vm_area_struct *prev = vma->vm_prev;

		/*
		* Is there a mapping abutting this one below?
		*
		* That's only ok if it's the same stack mapping
		* that has gotten split..
		*/
		if (prev && prev->vm_end == address)
		return prev->vm_flags & VM_GROWSDOWN ? 0 : -ENOMEM;

		expand_stack(vma, address);
		expand_stack(vma, address - PAGE_SIZE);
		}
		return 0;
		}

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