Commit df2a7df9 authored by Pedro Falcato's avatar Pedro Falcato Committed by Andrew Morton
Browse files

mm/munmap: replace can_modify_mm with can_modify_vma 

We were doing an extra mmap tree traversal just to check if the entire
range is modifiable.  This can be done when we iterate through the VMAs
instead.

Link: https://lkml.kernel.org/r/20240817-mseal-depessimize-v3-2-d8d2e037df30@gmail.com


Signed-off-by: default avatarPedro Falcato <pedro.falcato@gmail.com>
Reviewed-by: default avatarLiam R. Howlett <Liam.Howlett@Oracle.com>
LGTM, Reviewed-by: default avatarLorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Jeff Xu <jeffxu@chromium.org>
Cc: Kees Cook <kees@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 4d1b3416

mm/mmap.c

+1 −10
Original line number Diff line number Diff line
@@ -1740,16 +1740,7 @@ int do_vma_munmap(struct vma_iterator *vmi, struct vm_area_struct *vma, 
		unsigned long start, unsigned long end, struct list_head *uf,

		bool unlock)

{

	struct mm_struct *mm = vma->vm_mm;



	/*

	 * Check if memory is sealed, prevent unmapping a sealed VMA.

	 * can_modify_mm assumes we have acquired the lock on MM.

	 */

	if (unlikely(!can_modify_mm(mm, start, end)))

		return -EPERM;



	return do_vmi_align_munmap(vmi, vma, mm, start, end, uf, unlock);

	return do_vmi_align_munmap(vmi, vma, vma->vm_mm, start, end, uf, unlock);

}



/*

mm/vma.c

+12 −7
Original line number Diff line number Diff line
@@ -712,6 +712,12 @@ do_vmi_align_munmap(struct vma_iterator *vmi, struct vm_area_struct *vma, 
		if (end < vma->vm_end && mm->map_count >= sysctl_max_map_count)

			goto map_count_exceeded;



		/* Don't bother splitting the VMA if we can't unmap it anyway */

		if (!can_modify_vma(vma)) {

			error = -EPERM;

			goto start_split_failed;

		}



		error = __split_vma(vmi, vma, start, 1);

		if (error)

			goto start_split_failed;
@@ -723,6 +729,11 @@ do_vmi_align_munmap(struct vma_iterator *vmi, struct vm_area_struct *vma, 
	 */

	next = vma;

	do {

		if (!can_modify_vma(next)) {

			error = -EPERM;

			goto modify_vma_failed;

		}



		/* Does it split the end? */

		if (next->vm_end > end) {

			error = __split_vma(vmi, next, end, 0);
@@ -815,6 +826,7 @@ do_vmi_align_munmap(struct vma_iterator *vmi, struct vm_area_struct *vma, 
	__mt_destroy(&mt_detach);

	return 0;



modify_vma_failed:

clear_tree_failed:

userfaultfd_error:

munmap_gather_failed:
@@ -860,13 +872,6 @@ int do_vmi_munmap(struct vma_iterator *vmi, struct mm_struct *mm, 
	if (end == start)

		return -EINVAL;



	/*

	 * Check if memory is sealed, prevent unmapping a sealed VMA.

	 * can_modify_mm assumes we have acquired the lock on MM.

	 */

	if (unlikely(!can_modify_mm(mm, start, end)))

		return -EPERM;



	/* Find the first overlapping VMA */

	vma = vma_find(vmi, end);

	if (!vma) {