diff options
| author | Liam Howlett <liam.howlett@oracle.com> | 2022-10-18 19:17:12 +0000 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2022-10-20 21:27:23 -0700 |
| commit | a57b70519d1f7c53be98478623652738e5ac70d5 (patch) | |
| tree | 625e504bf350f9a976ed21978855ca851cb349ff | |
| parent | 1cd916d0340d0f45b151599c24ec40b5b2fd8e4a (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>
| -rw-r--r-- | mm/mmap.c | 15 |
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; } |