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/
Closes: https://lore.kernel.org/linux-mm/CAG48ez12VN1JAOtTNMY+Y2YnsU45yL5giS-Qn=ejtiHpgJAbdQ@mail.gmail.com/
Fixes: 18b098af2890 ("vma_merge: set vma iterator to correct position.")
Cc: [email protected]
Cc: Jann Horn <[email protected]>
Signed-off-by: Liam R. Howlett <[email protected]>
---
mm/mmap.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/mm/mmap.c b/mm/mmap.c
index b56a7f0c9f85..acb7dea49e23 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -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;
}
/*
--
2.40.1
On Fri, Sep 29, 2023 at 02:30:39PM -0400, Liam R. Howlett wrote:
> 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/
> Closes: https://lore.kernel.org/linux-mm/CAG48ez12VN1JAOtTNMY+Y2YnsU45yL5giS-Qn=ejtiHpgJAbdQ@mail.gmail.com/
> Fixes: 18b098af2890 ("vma_merge: set vma iterator to correct position.")
> Cc: [email protected]
> Cc: Jann Horn <[email protected]>
> Signed-off-by: Liam R. Howlett <[email protected]>
> ---
> mm/mmap.c | 10 ++++++++--
> 1 file changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/mm/mmap.c b/mm/mmap.c
> index b56a7f0c9f85..acb7dea49e23 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -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;
> }
>
> /*
> --
> 2.40.1
>
Looks good to me,
Reviewed-by: Lorenzo Stoakes <[email protected]>
On 9/29/23 20:30, Liam R. Howlett wrote:
> 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/
> Closes: https://lore.kernel.org/linux-mm/CAG48ez12VN1JAOtTNMY+Y2YnsU45yL5giS-Qn=ejtiHpgJAbdQ@mail.gmail.com/
> Fixes: 18b098af2890 ("vma_merge: set vma iterator to correct position.")
> Cc: [email protected]
> Cc: Jann Horn <[email protected]>
> Signed-off-by: Liam R. Howlett <[email protected]>
Acked-by: Vlastimil Babka <[email protected]>
> ---
> mm/mmap.c | 10 ++++++++--
> 1 file changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/mm/mmap.c b/mm/mmap.c
> index b56a7f0c9f85..acb7dea49e23 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -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;
> }
>
> /*