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authorLiu Zixian <liuzixian4@huawei.com>2020-12-05 22:15:15 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2020-12-06 10:19:07 -0800
commit309d08d9b3a3659ab3f239d27d4e38b670b08fc9 (patch)
tree989f191d033e2a58ba5d546bc2782036c9daf173 /mm/mmap.c
parent7a5bde37983d37783161681ff7c6122dfd081791 (diff)
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. We have a driver which changes vm_flags, and this bug is found by our testcases. Fixes: d70cec898324 ("mm: mmap: merge vma after call_mmap() if possible") Signed-off-by: Liu Zixian <liuzixian4@huawei.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Reviewed-by: Jason Gunthorpe <jgg@nvidia.com> Reviewed-by: David Hildenbrand <david@redhat.com> Cc: Miaohe Lin <linmiaohe@huawei.com> Cc: Hongxiang Lou <louhongxiang@huawei.com> Cc: Hu Shiyuan <hushiyuan@huawei.com> Cc: Matthew Wilcox <willy@infradead.org> Link: https://lkml.kernel.org/r/20201203085350.22624-1-liuzixian4@huawei.com Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/mmap.c')
-rw-r--r--mm/mmap.c26
1 files 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);