Commit 1419430c authored by Liam R. Howlett's avatar Liam R. Howlett Committed by Andrew Morton
Browse files

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: 18b098af ("vma_merge: set vma iterator to correct position.")
Signed-off-by: default avatarLiam R. Howlett <Liam.Howlett@oracle.com>
Reported-by: default avatarJann Horn <jannh@google.com>
Closes: https://lore.kernel.org/linux-mm/CAG48ez12VN1JAOtTNMY+Y2YnsU45yL5giS-Qn=ejtiHpgJAbdQ@mail.gmail.com/


Reviewed-by: default avatarLorenzo Stoakes <lstoakes@gmail.com>
Acked-by: default avatarVlastimil 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: default avatarAndrew Morton <akpm@linux-foundation.org>
parent e0f81ab1

mm/mmap.c

+8 −2
Original line number Diff line number Diff line
@@ -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;

}



/*