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mmap: fix error paths with dup_anon_vma() 

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/20230929183041.2835469-3-Liam.Howlett@oracle.com
Fixes: d4af56c5c7 ("mm: start tracking VMAs with maple tree")
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Reviewed-by: Lorenzo Stoakes <lstoakes@gmail.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Jann Horn <jannh@google.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Liam R. Howlett 2023-09-29 14:30:40 -04:00 committed by Andrew Morton
parent 1419430c8a
commit 824135c46b
1 changed files with 22 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

30
mm/mmap.c
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@ -583,11 +583,12 @@ static inline void vma_complete(struct vma_prepare *vp,
* dup_anon_vma() - Helper function to duplicate anon_vma
* @dst: The destination VMA
* @src: The source VMA
* @dup: Pointer to the destination VMA when successful.
*
* 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
@ -595,9 +596,15 @@ static inline int dup_anon_vma(struct vm_area_struct *dst,
* anon pages imported.
*/
if (src->anon_vma && !dst->anon_vma) {
int ret;
vma_assert_write_locked(dst);
dst->anon_vma = src->anon_vma;
return anon_vma_clone(dst, src);
ret = anon_vma_clone(dst, src);
if (ret)
return ret;
*dup = dst;
}
return 0;
@ -624,6 +631,7 @@ int vma_expand(struct vma_iterator *vmi, struct vm_area_struct *vma,
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 +641,7 @@ int vma_expand(struct vma_iterator *vmi, struct vm_area_struct *vma,
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 +669,8 @@ int vma_expand(struct vma_iterator *vmi, struct vm_area_struct *vma,
return 0;
nomem:
if (anon_dup)
unlink_anon_vmas(anon_dup);
return -ENOMEM;
}
@ -860,6 +870,7 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm,
{
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 +938,18 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm,
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 +965,7 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm,
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
@ -968,7 +979,7 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm,
vma_pgoff = curr->vm_pgoff;
vma_start_write(curr);
remove = curr;
err = dup_anon_vma(next, curr);
err = dup_anon_vma(next, curr, &anon_dup);
}
}
}
@ -1018,6 +1029,9 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm,
return res;
prealloc_fail:
if (anon_dup)
unlink_anon_vmas(anon_dup);
anon_vma_fail:
vma_iter_set(vmi, addr);
vma_iter_load(vmi);