On 12/6/24 23:50, Lorenzo Stoakes wrote:
> It is of critical importance to check the return results on VMA merge (and
> split), failure to do so can result in use-after-free's. This bug has
> recurred, so have the compiler enforce this check to prevent any future
> repetition.
>
> Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@xxxxxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
> ---
> mm/vma.c | 8 +++++---
> mm/vma.h | 26 +++++++++++++++-----------
> 2 files changed, 20 insertions(+), 14 deletions(-)
>
> diff --git a/mm/vma.c b/mm/vma.c
> index a06747845cac..543c102b4062 100644
> --- a/mm/vma.c
> +++ b/mm/vma.c
> @@ -447,8 +447,9 @@ void unmap_region(struct ma_state *mas, struct vm_area_struct *vma,
> * has already been checked or doesn't make sense to fail.
> * VMA Iterator will point to the original VMA.
> */
> -static int __split_vma(struct vma_iterator *vmi, struct vm_area_struct *vma,
> - unsigned long addr, int new_below)
> +static __must_check int
> +__split_vma(struct vma_iterator *vmi, struct vm_area_struct *vma,
> + unsigned long addr, int new_below)
> {
> struct vma_prepare vp;
> struct vm_area_struct *new;
> @@ -710,7 +711,8 @@ static bool can_merge_remove_vma(struct vm_area_struct *vma)
> * - The caller must hold a WRITE lock on the mm_struct->mmap_lock.
> * - vmi must be positioned within [@vmg->vma->vm_start, @vmg->vma->vm_end).
> */
> -static struct vm_area_struct *vma_merge_existing_range(struct vma_merge_struct *vmg)
> +static __must_check struct vm_area_struct *vma_merge_existing_range(
> + struct vma_merge_struct *vmg)
> {
> struct vm_area_struct *vma = vmg->vma;
> struct vm_area_struct *prev = vmg->prev;
> diff --git a/mm/vma.h b/mm/vma.h
> index 295d44ea54db..61ed044b6145 100644
> --- a/mm/vma.h
> +++ b/mm/vma.h
> @@ -139,9 +139,10 @@ void validate_mm(struct mm_struct *mm);
> #define validate_mm(mm) do { } while (0)
> #endif
>
> -int vma_expand(struct vma_merge_struct *vmg);
> -int vma_shrink(struct vma_iterator *vmi, struct vm_area_struct *vma,
> - unsigned long start, unsigned long end, pgoff_t pgoff);
> +__must_check int vma_expand(struct vma_merge_struct *vmg);
> +__must_check int vma_shrink(struct vma_iterator *vmi,
> + struct vm_area_struct *vma,
> + unsigned long start, unsigned long end, pgoff_t pgoff);
>
> static inline int vma_iter_store_gfp(struct vma_iterator *vmi,
> struct vm_area_struct *vma, gfp_t gfp)
> @@ -174,13 +175,14 @@ void unmap_region(struct ma_state *mas, struct vm_area_struct *vma,
> struct vm_area_struct *prev, struct vm_area_struct *next);
>
> /* We are about to modify the VMA's flags. */
> -struct vm_area_struct *vma_modify_flags(struct vma_iterator *vmi,
> +__must_check struct vm_area_struct
> +*vma_modify_flags(struct vma_iterator *vmi,
> struct vm_area_struct *prev, struct vm_area_struct *vma,
> unsigned long start, unsigned long end,
> unsigned long new_flags);
>
> /* We are about to modify the VMA's flags and/or anon_name. */
> -struct vm_area_struct
> +__must_check struct vm_area_struct
> *vma_modify_flags_name(struct vma_iterator *vmi,
> struct vm_area_struct *prev,
> struct vm_area_struct *vma,
> @@ -190,7 +192,7 @@ struct vm_area_struct
> struct anon_vma_name *new_name);
>
> /* We are about to modify the VMA's memory policy. */
> -struct vm_area_struct
> +__must_check struct vm_area_struct
> *vma_modify_policy(struct vma_iterator *vmi,
> struct vm_area_struct *prev,
> struct vm_area_struct *vma,
> @@ -198,7 +200,7 @@ struct vm_area_struct
> struct mempolicy *new_pol);
>
> /* We are about to modify the VMA's flags and/or uffd context. */
> -struct vm_area_struct
> +__must_check struct vm_area_struct
> *vma_modify_flags_uffd(struct vma_iterator *vmi,
> struct vm_area_struct *prev,
> struct vm_area_struct *vma,
> @@ -206,11 +208,13 @@ struct vm_area_struct
> unsigned long new_flags,
> struct vm_userfaultfd_ctx new_ctx);
>
> -struct vm_area_struct *vma_merge_new_range(struct vma_merge_struct *vmg);
> +__must_check struct vm_area_struct
> +*vma_merge_new_range(struct vma_merge_struct *vmg);
>
> -struct vm_area_struct *vma_merge_extend(struct vma_iterator *vmi,
> - struct vm_area_struct *vma,
> - unsigned long delta);
> +__must_check struct vm_area_struct
> +*vma_merge_extend(struct vma_iterator *vmi,
> + struct vm_area_struct *vma,
> + unsigned long delta);
>
> void unlink_file_vma_batch_init(struct unlink_vma_file_batch *vb);
>
