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mm/mremap: fix vm_pgoff in vma_merge() case 3 

After upgrading build guests to v6.3, rpm started segfaulting for
specific packages, which was bisected to commit 0503ea8f5b ("mm/mmap:
remove __vma_adjust()"). rpm is doing many mremap() operations with file
mappings of its db. The problem is that in vma_merge() case 3 (we merge
with the next vma, expanding it downwards) vm_pgoff is not adjusted as
it should when vm_start changes. As a result the rpm process most likely
sees data from the wrong offset of the file. Fix the vm_pgoff
calculation.

For case 8 this is a non-functional change as the resulting vm_pgoff is
the same.

Reported-and-bisected-by: Jiri Slaby <jirislaby@kernel.org>
Reported-and-tested-by: Fabian Vogt <fvogt@suse.com>
Link: https://bugzilla.suse.com/show_bug.cgi?id=1210903
Fixes: 0503ea8f5b ("mm/mmap: remove __vma_adjust()")
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Cc: <stable@vger.kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Vlastimil Babka 2023-04-27 16:09:59 +02:00 committed by Linus Torvalds
parent 6e98b09da9
commit 7e7757876f
1 changed files with 1 additions and 1 deletions
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2
mm/mmap.c
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@ -978,7 +978,7 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm,
vma = next; /* case 3 */
vma_start = addr;
vma_end = next->vm_end;
vma_pgoff = mid->vm_pgoff;
vma_pgoff = next->vm_pgoff - pglen;
err = 0;
if (mid != next) { /* case 8 */
remove = mid;