mmap: fix error paths with dup_anon_vma()

commit 824135c upstream.

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: d4af56c ("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>
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

mm/mmap.c

@@ -519,6 +519,7 @@ inline int vma_expand(struct ma_state *mas, struct vm_area_struct *vma,
 	struct anon_vma *anon_vma = vma->anon_vma;
 	struct file *file = vma->vm_file;
 	bool remove_next = false;
+	struct vm_area_struct *anon_dup = NULL;
 
 	if (next && (vma != next) && (end == next->vm_end)) {
 		remove_next = true;
@@ -530,6 +531,8 @@ inline int vma_expand(struct ma_state *mas, struct vm_area_struct *vma,
 			error = anon_vma_clone(vma, next);
 			if (error)
 				return error;
+
+			anon_dup = vma;
 		}
 	}
 
@@ -602,6 +605,9 @@ inline int vma_expand(struct ma_state *mas, struct vm_area_struct *vma,
 	return 0;
 
 nomem:
+	if (anon_dup)
+		unlink_anon_vmas(anon_dup);
+
 	return -ENOMEM;
 }
 
@@ -629,6 +635,7 @@ int __vma_adjust(struct vm_area_struct *vma, unsigned long start,
 	int remove_next = 0;
 	MA_STATE(mas, &mm->mm_mt, 0, 0);
 	struct vm_area_struct *exporter = NULL, *importer = NULL;
+	struct vm_area_struct *anon_dup = NULL;
 
 	if (next && !insert) {
 		if (end >= next->vm_end) {
@@ -709,11 +716,17 @@ int __vma_adjust(struct vm_area_struct *vma, unsigned long start,
 			error = anon_vma_clone(importer, exporter);
 			if (error)
 				return error;
+
+			anon_dup = importer;
 		}
 	}
 
-	if (mas_preallocate(&mas, vma, GFP_KERNEL))
+	if (mas_preallocate(&mas, vma, GFP_KERNEL)) {
+		if (anon_dup)
+			unlink_anon_vmas(anon_dup);
+
 		return -ENOMEM;
+	}
 
 	vma_adjust_trans_huge(orig_vma, start, end, adjust_next);
 	if (file) {