Commit a09a79f6 authored by Mikulas Patocka's avatar Mikulas Patocka Committed by Linus Torvalds
Browse files

Don't lock guardpage if the stack is growing up 



Linux kernel excludes guard page when performing mlock on a VMA with
down-growing stack. However, some architectures have up-growing stack
and locking the guard page should be excluded in this case too.

This patch fixes lvm2 on PA-RISC (and possibly other architectures with
up-growing stack). lvm2 calculates number of used pages when locking and
when unlocking and reports an internal error if the numbers mismatch.

[ Patch changed fairly extensively to also fix /proc/<pid>/maps for the
  grows-up case, and to move things around a bit to clean it all up and
  share the infrstructure with the /proc bits.

  Tested on ia64 that has both grow-up and grow-down segments  - Linus ]

Signed-off-by: default avatarMikulas Patocka <mikulas@artax.karlin.mff.cuni.cz>
Tested-by: default avatarTony Luck <tony.luck@gmail.com>
Cc: stable@kernel.org
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 26822eeb

fs/proc/task_mmu.c

+7 −5
Original line number Diff line number Diff line
@@ -214,7 +214,7 @@ static void show_map_vma(struct seq_file *m, struct vm_area_struct *vma) 
	int flags = vma->vm_flags;

	unsigned long ino = 0;

	unsigned long long pgoff = 0;

	unsigned long start;

	unsigned long start, end;

	dev_t dev = 0;

	int len;
@@ -227,13 +227,15 @@ static void show_map_vma(struct seq_file *m, struct vm_area_struct *vma) 


	/* We don't show the stack guard page in /proc/maps */

	start = vma->vm_start;

	if (vma->vm_flags & VM_GROWSDOWN)

		if (!vma_stack_continue(vma->vm_prev, vma->vm_start))

	if (stack_guard_page_start(vma, start))

		start += PAGE_SIZE;

	end = vma->vm_end;

	if (stack_guard_page_end(vma, end))

		end -= PAGE_SIZE;



	seq_printf(m, "%08lx-%08lx %c%c%c%c %08llx %02x:%02x %lu %n",

			start,

			vma->vm_end,

			end,

			flags & VM_READ ? 'r' : '-',

			flags & VM_WRITE ? 'w' : '-',

			flags & VM_EXEC ? 'x' : '-',

include/linux/mm.h

+23 −1
Original line number Diff line number Diff line
@@ -1011,11 +1011,33 @@ int set_page_dirty_lock(struct page *page); 
int clear_page_dirty_for_io(struct page *page);



/* Is the vma a continuation of the stack vma above it? */

static inline int vma_stack_continue(struct vm_area_struct *vma, unsigned long addr)

static inline int vma_growsdown(struct vm_area_struct *vma, unsigned long addr)

{

	return vma && (vma->vm_end == addr) && (vma->vm_flags & VM_GROWSDOWN);

}



static inline int stack_guard_page_start(struct vm_area_struct *vma,

					     unsigned long addr)

{

	return (vma->vm_flags & VM_GROWSDOWN) &&

		(vma->vm_start == addr) &&

		!vma_growsdown(vma->vm_prev, addr);

}



/* Is the vma a continuation of the stack vma below it? */

static inline int vma_growsup(struct vm_area_struct *vma, unsigned long addr)

{

	return vma && (vma->vm_start == addr) && (vma->vm_flags & VM_GROWSUP);

}



static inline int stack_guard_page_end(struct vm_area_struct *vma,

					   unsigned long addr)

{

	return (vma->vm_flags & VM_GROWSUP) &&

		(vma->vm_end == addr) &&

		!vma_growsup(vma->vm_next, addr);

}



extern unsigned long move_page_tables(struct vm_area_struct *vma,

		unsigned long old_addr, struct vm_area_struct *new_vma,

		unsigned long new_addr, unsigned long len);

mm/memory.c

+7 −9
Original line number Diff line number Diff line
@@ -1412,9 +1412,8 @@ no_page_table: 


static inline int stack_guard_page(struct vm_area_struct *vma, unsigned long addr)

{

	return (vma->vm_flags & VM_GROWSDOWN) &&

		(vma->vm_start == addr) &&

		!vma_stack_continue(vma->vm_prev, addr);

	return stack_guard_page_start(vma, addr) ||

	       stack_guard_page_end(vma, addr+PAGE_SIZE);

}



/**
@@ -1551,12 +1550,6 @@ int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm, 
			continue;

		}



		/*

		 * For mlock, just skip the stack guard page.

		 */

		if ((gup_flags & FOLL_MLOCK) && stack_guard_page(vma, start))

			goto next_page;



		do {

			struct page *page;

			unsigned int foll_flags = gup_flags;
@@ -1573,6 +1566,11 @@ int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm, 
				int ret;

				unsigned int fault_flags = 0;



				/* For mlock, just skip the stack guard page. */

				if (foll_flags & FOLL_MLOCK) {

					if (stack_guard_page(vma, start))

						goto next_page;

				}

				if (foll_flags & FOLL_WRITE)

					fault_flags |= FAULT_FLAG_WRITE;

				if (nonblocking)

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