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authorLiam Howlett <liam.howlett@oracle.com>2022-10-18 19:17:12 +0000
committerAndrew Morton <akpm@linux-foundation.org>2022-10-20 21:27:23 -0700
commita57b70519d1f7c53be98478623652738e5ac70d5 (patch)
tree625e504bf350f9a976ed21978855ca851cb349ff /mm
parent1cd916d0340d0f45b151599c24ec40b5b2fd8e4a (diff)
mm/mmap: fix MAP_FIXED address return on VMA merge
mmap should return the start address of newly mapped area when successful. On a successful merge of a VMA, the return address was changed and thus was violating that expectation from userspace. This is a restoration of functionality provided by 309d08d9b3a3 (mm/mmap.c: fix mmap return value when vma is merged after call_mmap()). For completeness of fixing MAP_FIXED, implement the comments from the previous discussion to never update the address and fail if the address changes. Leaving the error as a WARN_ON() to avoid crashing the kernel. Link: https://lkml.kernel.org/r/20221018191613.4133459-1-Liam.Howlett@oracle.com Link: https://lore.kernel.org/all/Y06yk66SKxlrwwfb@lakrids/ Link: https://lore.kernel.org/all/20201203085350.22624-1-liuzixian4@huawei.com/ Fixes: 4dd1b84140c1 ("mm/mmap: use advanced maple tree API for mmap_region()") Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com> Reported-by: Mark Rutland <mark.rutland@arm.com> Cc: Liu Zixian <liuzixian4@huawei.com> Cc: David Hildenbrand <david@redhat.com> Cc: Jason Gunthorpe <jgg@nvidia.com> Cc: Matthew Wilcox <willy@infradead.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/mmap.c15
1 files changed, 7 insertions, 8 deletions
diff --git a/mm/mmap.c b/mm/mmap.c
index 721fe5c82a0e..e270057ed04e 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2626,14 +2626,14 @@ cannot_expand:
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
+ /*
+ * Expansion is handled above, merging is handled below.
+ * Drivers should not alter the address of the VMA.
*/
- WARN_ON_ONCE(addr != vma->vm_start);
-
- addr = vma->vm_start;
+ if (WARN_ON((addr != vma->vm_start))) {
+ error = -EINVAL;
+ goto close_and_free_vma;
+ }
mas_reset(&mas);
/*
@@ -2655,7 +2655,6 @@ cannot_expand:
vm_area_free(vma);
vma = merge;
/* Update vm_flags to pick up the change. */
- addr = vma->vm_start;
vm_flags = vma->vm_flags;
goto unmap_writable;
}