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Commit 87e8827b authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Linus Torvalds
Browse files

mm: fix the racy mm->locked_vm change in 



"mm->locked_vm += grow" and vm_stat_account() in acct_stack_growth() are
not safe; multiple threads using the same ->mm can do this at the same
time trying to expans different vma's under down_read(mmap_sem).  This
means that one of the "locked_vm += grow" changes can be lost and we can
miss munlock_vma_pages_all() later.

Move this code into the caller(s) under mm->page_table_lock.  All other
updates to ->locked_vm hold mmap_sem for writing.

Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Acked-by: default avatarHugh Dickins <hughd@google.com>
Cc: Andrey Konovalov <andreyknvl@google.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Sasha Levin <sasha.levin@oracle.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 9fd745d4

mm/mmap.c

+8 −4
Original line number Diff line number Diff line
@@ -2138,10 +2138,6 @@ static int acct_stack_growth(struct vm_area_struct *vma, unsigned long size, uns 
	if (security_vm_enough_memory_mm(mm, grow))

		return -ENOMEM;



	/* Ok, everything looks good - let it rip */

	if (vma->vm_flags & VM_LOCKED)

		mm->locked_vm += grow;

	vm_stat_account(mm, vma->vm_flags, vma->vm_file, grow);

	return 0;

}
@@ -2202,6 +2198,10 @@ int expand_upwards(struct vm_area_struct *vma, unsigned long address) 
				 * against concurrent vma expansions.

				 */

				spin_lock(&vma->vm_mm->page_table_lock);

				if (vma->vm_flags & VM_LOCKED)

					vma->vm_mm->locked_vm += grow;

				vm_stat_account(vma->vm_mm, vma->vm_flags,

						vma->vm_file, grow);

				anon_vma_interval_tree_pre_update_vma(vma);

				vma->vm_end = address;

				anon_vma_interval_tree_post_update_vma(vma);
@@ -2273,6 +2273,10 @@ int expand_downwards(struct vm_area_struct *vma, 
				 * against concurrent vma expansions.

				 */

				spin_lock(&vma->vm_mm->page_table_lock);

				if (vma->vm_flags & VM_LOCKED)

					vma->vm_mm->locked_vm += grow;

				vm_stat_account(vma->vm_mm, vma->vm_flags,

						vma->vm_file, grow);

				anon_vma_interval_tree_pre_update_vma(vma);

				vma->vm_start = address;

				vma->vm_pgoff -= grow;