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mmap: fix vma_iterator in error path of vma_merge() 

During the error path, the vma iterator may not be correctly positioned or
set to the correct range.  Undo the vma_prev() call by resetting to the
passed in address.  Re-walking to the same range will fix the range to the
area previously passed in.

Users would notice increased cycles as vma_merge() would be called an
extra time with vma == prev, and thus would fail to merge and return.

Link: https://lore.kernel.org/linux-mm/CAG48ez12VN1JAOtTNMY+Y2YnsU45yL5giS-Qn=ejtiHpgJAbdQ@mail.gmail.com/
Link: https://lkml.kernel.org/r/20230929183041.2835469-2-Liam.Howlett@oracle.com
Fixes: 18b098af28 ("vma_merge: set vma iterator to correct position.")
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Reported-by: Jann Horn <jannh@google.com>
Closes: https://lore.kernel.org/linux-mm/CAG48ez12VN1JAOtTNMY+Y2YnsU45yL5giS-Qn=ejtiHpgJAbdQ@mail.gmail.com/
Reviewed-by: Lorenzo Stoakes <lstoakes@gmail.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Liam R. Howlett 2023-09-29 14:30:39 -04:00 committed by Andrew Morton
parent e0f81ab1e4
commit 1419430c8a
1 changed files with 8 additions and 2 deletions
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10
mm/mmap.c
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@ -975,7 +975,7 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm,
/* Error in anon_vma clone. */
if (err)
return NULL;
goto anon_vma_fail;
if (vma_start < vma->vm_start || vma_end > vma->vm_end)
vma_expanded = true;
@ -988,7 +988,7 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm,
}
if (vma_iter_prealloc(vmi, vma))
return NULL;
goto prealloc_fail;
init_multi_vma_prep(&vp, vma, adjust, remove, remove2);
VM_WARN_ON(vp.anon_vma && adjust && adjust->anon_vma &&
@ -1016,6 +1016,12 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm,
vma_complete(&vp, vmi, mm);
khugepaged_enter_vma(res, vm_flags);
return res;
prealloc_fail:
anon_vma_fail:
vma_iter_set(vmi, addr);
vma_iter_load(vmi);
return NULL;
}
/*