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.
Fixes: d70cec898324 ("mm: mmap: merge vma after call_mmap() if possible")
Signed-off-by: Liu Zixian <liuzixian4@xxxxxxxxxx>
---
v2:
We want to do "addr = vma->vm_start;" unconditionally,
so move assignment to addr before if(unlikely) block.
---
mm/mmap.c | 26 ++++++++++++--------------
1 file changed, 12 insertions(+), 14 deletions(-)
diff --git a/mm/mmap.c b/mm/mmap.c
index d91ecb00d38c..5c8b4485860d 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1808,6 +1808,17 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
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 *file, unsigned long addr,
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);
--
2.23.0
