@@ -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);
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 Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next and is updated there every 3-4 working days ------------------------------------------------------ From: Liu Zixian <liuzixian4@huawei.com> 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@huawei.com Fixes: d70cec898324 ("mm: mmap: merge vma after call_mmap() if possible") Signed-off-by: Liu Zixian <liuzixian4@huawei.com> Cc: Miaohe Lin <linmiaohe@huawei.com> Cc: Hongxiang Lou <louhongxiang@huawei.com> Cc: Hu Shiyuan <hushiyuan@huawei.com> Cc: David Hildenbrand <david@redhat.com> Cc: Jason Gunthorpe <jgg@ziepe.ca> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> --- mm/mmap.c | 26 ++++++++++++-------------- 1 file changed, 12 insertions(+), 14 deletions(-)