The patch titled
Subject: mmap: fix error paths with dup_anon_vma()
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
mmap-fix-error-paths-with-dup_anon_vma.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mmap-fix-error-paths-with-dup_anon_vma.patch
This patch will later appear in the mm-hotfixes-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: "Liam R. Howlett" <Liam.Howlett@xxxxxxxxxx>
Subject: mmap: fix error paths with dup_anon_vma()
Date: Wed, 27 Sep 2023 12:07:45 -0400
When the calling function fails after the dup_anon_vma(), the duplication
of the anon_vma is not being undone. Add the necessary unlink_anon_vma()
call to the error paths that are missing them.
This issue showed up during inspection of the error path in vma_merge()
for an unrelated vma iterator issue.
Users may experience increased memory usage, which may be problematic as
the failure would likely be caused by a low memory situation.
Link: https://lkml.kernel.org/r/20230927160746.1928098-3-Liam.Howlett@xxxxxxxxxx
Fixes: d4af56c5c7c6 ("mm: start tracking VMAs with maple tree")
Cc: Jann Horn <jannh@xxxxxxxxxx>
Signed-off-by: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/mmap.c | 20 ++++++++++++++------
1 file changed, 14 insertions(+), 6 deletions(-)
--- a/mm/mmap.c~mmap-fix-error-paths-with-dup_anon_vma
+++ a/mm/mmap.c
@@ -587,7 +587,7 @@ again:
* Returns: 0 on success.
*/
static inline int dup_anon_vma(struct vm_area_struct *dst,
- struct vm_area_struct *src)
+ struct vm_area_struct *src, struct vm_area_struct **dup)
{
/*
* Easily overlooked: when mprotect shifts the boundary, make sure the
@@ -597,6 +597,7 @@ static inline int dup_anon_vma(struct vm
if (src->anon_vma && !dst->anon_vma) {
vma_assert_write_locked(dst);
dst->anon_vma = src->anon_vma;
+ *dup = dst;
return anon_vma_clone(dst, src);
}
@@ -624,6 +625,7 @@ int vma_expand(struct vma_iterator *vmi,
unsigned long start, unsigned long end, pgoff_t pgoff,
struct vm_area_struct *next)
{
+ struct vm_area_struct *anon_dup = NULL;
bool remove_next = false;
struct vma_prepare vp;
@@ -633,7 +635,7 @@ int vma_expand(struct vma_iterator *vmi,
remove_next = true;
vma_start_write(next);
- ret = dup_anon_vma(vma, next);
+ ret = dup_anon_vma(vma, next, &anon_dup);
if (ret)
return ret;
}
@@ -661,6 +663,8 @@ int vma_expand(struct vma_iterator *vmi,
return 0;
nomem:
+ if (anon_dup)
+ unlink_anon_vmas(anon_dup);
return -ENOMEM;
}
@@ -860,6 +864,7 @@ struct vm_area_struct *vma_merge(struct
{
struct vm_area_struct *curr, *next, *res;
struct vm_area_struct *vma, *adjust, *remove, *remove2;
+ struct vm_area_struct *anon_dup = NULL;
struct vma_prepare vp;
pgoff_t vma_pgoff;
int err = 0;
@@ -927,18 +932,18 @@ struct vm_area_struct *vma_merge(struct
vma_start_write(next);
remove = next; /* case 1 */
vma_end = next->vm_end;
- err = dup_anon_vma(prev, next);
+ err = dup_anon_vma(prev, next, &anon_dup);
if (curr) { /* case 6 */
vma_start_write(curr);
remove = curr;
remove2 = next;
if (!next->anon_vma)
- err = dup_anon_vma(prev, curr);
+ err = dup_anon_vma(prev, curr, &anon_dup);
}
} else if (merge_prev) { /* case 2 */
if (curr) {
vma_start_write(curr);
- err = dup_anon_vma(prev, curr);
+ err = dup_anon_vma(prev, curr, &anon_dup);
if (end == curr->vm_end) { /* case 7 */
remove = curr;
} else { /* case 5 */
@@ -954,7 +959,7 @@ struct vm_area_struct *vma_merge(struct
vma_end = addr;
adjust = next;
adj_start = -(prev->vm_end - addr);
- err = dup_anon_vma(next, prev);
+ err = dup_anon_vma(next, prev, &anon_dup);
} else {
/*
* Note that cases 3 and 8 are the ONLY ones where prev
@@ -1018,6 +1023,9 @@ struct vm_area_struct *vma_merge(struct
return res;
prealloc_fail:
+ if (anon_dup)
+ unlink_anon_vmas(anon_dup);
+
anon_vma_fail:
if (merge_prev)
vma_next(vmi);
_
Patches currently in -mm which might be from Liam.Howlett@xxxxxxxxxx are
maple_tree-add-mas_active-to-detect-in-tree-walks.patch
maple_tree-add-mas_underflow-and-mas_overflow-states.patch
mmap-fix-vma_iterator-in-error-path-of-vma_merge.patch
mmap-fix-error-paths-with-dup_anon_vma.patch
mmap-add-clarifying-comment-to-vma_merge-code.patch
