From df2a7df9a9aa32c3df227de346693e6e802c8591 Mon Sep 17 00:00:00 2001
From: Pedro Falcato <pedro.falcato@gmail.com>
Date: Sat, 17 Aug 2024 01:18:29 +0100
Subject: [PATCH] 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: Pedro Falcato <pedro.falcato@gmail.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
LGTM, Reviewed-by: Lorenzo 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: Andrew Morton <akpm@linux-foundation.org>
---
mm/mmap.c | 11 +----------
mm/vma.c | 19 ++++++++++++-------
2 files changed, 13 insertions(+), 17 deletions(-)
diff --git a/mm/mmap.c b/mm/mmap.c
index 7cba84f8e3a58..548bc45a27bf8 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -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);
}
/*
diff --git a/mm/vma.c b/mm/vma.c
index 84965f2cd5800..5850f7c0949b0 100644
--- a/mm/vma.c
+++ b/mm/vma.c
@@ -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) {
--
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