The patch titled
Subject: mm/mmap.c: fix mmap return value when vma is merged after call_mmap()
has been added to the -mm tree. Its filename is
fix-mmap-return-value-when-vma-is-merged-after-call_mmap.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/fix-mmap-return-value-when-vma-is-merged-after-call_mmap.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/fix-mmap-return-value-when-vma-is-merged-after-call_mmap.patch
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------------------------------------------------------
From: Liu Zixian <liuzixian4@xxxxxxxxxx>
Subject: mm/mmap.c: fix mmap return value when vma is merged after call_mmap()
On success, mmap should return the begin address of newly mapped area, but
patch "mm: mmap: merge vma after call_mmap() if possible" set vm_start of
newly merged vma to return value addr. Users of mmap will get wrong
address if vma is merged after call_mmap(). We fix this by moving the
assignment to addr before merging vma.
Link: https://lkml.kernel.org/r/20201203085350.22624-1-liuzixian4@xxxxxxxxxx
Fixes: d70cec898324 ("mm: mmap: merge vma after call_mmap() if possible")
Signed-off-by: Liu Zixian <liuzixian4@xxxxxxxxxx>
Cc: Miaohe Lin <linmiaohe@xxxxxxxxxx>
Cc: Hongxiang Lou <louhongxiang@xxxxxxxxxx>
Cc: Hu Shiyuan <hushiyuan@xxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Jason Gunthorpe <jgg@xxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/mmap.c | 26 ++++++++++++--------------
1 file changed, 12 insertions(+), 14 deletions(-)
--- a/mm/mmap.c~fix-mmap-return-value-when-vma-is-merged-after-call_mmap
+++ a/mm/mmap.c
@@ -1808,6 +1808,17 @@ unsigned long mmap_region(struct file *f
if (error)
goto unmap_and_free_vma;
+ /* Can addr have changed??
+ *
+ * Answer: Yes, several device drivers can do it in their
+ * f_op->mmap method. -DaveM
+ * Bug: If addr is changed, prev, rb_link, rb_parent should
+ * be updated for vma_link()
+ */
+ WARN_ON_ONCE(addr != vma->vm_start);
+
+ addr = vma->vm_start;
+
/* If vm_flags changed after call_mmap(), we should try merge vma again
* as we may succeed this time.
*/
@@ -1822,25 +1833,12 @@ unsigned long mmap_region(struct file *f
fput(vma->vm_file);
vm_area_free(vma);
vma = merge;
- /* Update vm_flags and possible addr to pick up the change. We don't
- * warn here if addr changed as the vma is not linked by vma_link().
- */
- addr = vma->vm_start;
+ /* Update vm_flags to pick up the change. */
vm_flags = vma->vm_flags;
goto unmap_writable;
}
}
- /* Can addr have changed??
- *
- * Answer: Yes, several device drivers can do it in their
- * f_op->mmap method. -DaveM
- * Bug: If addr is changed, prev, rb_link, rb_parent should
- * be updated for vma_link()
- */
- WARN_ON_ONCE(addr != vma->vm_start);
-
- addr = vma->vm_start;
vm_flags = vma->vm_flags;
} else if (vm_flags & VM_SHARED) {
error = shmem_zero_setup(vma);
_
Patches currently in -mm which might be from liuzixian4@xxxxxxxxxx are
fix-mmap-return-value-when-vma-is-merged-after-call_mmap.patch
