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.
Fixes: d4af56c5c7c6 ("mm: start tracking VMAs with maple tree") Cc: stable@vger.kernel.org Cc: Jann Horn jannh@google.com Signed-off-by: Liam R. Howlett Liam.Howlett@oracle.com --- mm/mmap.c | 20 ++++++++++++++------ 1 file changed, 14 insertions(+), 6 deletions(-)
diff --git a/mm/mmap.c b/mm/mmap.c index b5bc4ca9bdc4..2f0ee489db8a 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -587,7 +587,7 @@ static inline void vma_complete(struct vma_prepare *vp, * 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_area_struct *dst, 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, 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 +635,7 @@ 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 +663,8 @@ 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 +864,7 @@ 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 +932,18 @@ 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 +959,7 @@ 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 @@ -1018,6 +1023,9 @@ 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: if (merge_prev) vma_next(vmi);