On 09/15/25 at 03:40pm, Uladzislau Rezki (Sony) wrote:
> __vmalloc_area_node() may call free_vmap_area() or vfree() on
> error paths, both of which can sleep. This becomes problematic
> if the function is invoked from an atomic context, such as when
> GFP_ATOMIC or GFP_NOWAIT is passed via gfp_mask.
>
> To fix this, unify error paths and defer the cleanup of partly
> initialized vm_struct objects to a workqueue. This ensures that
> freeing happens in a process context and avoids invalid sleeps
> in atomic regions.
>
> Acked-by: Michal Hocko <mhocko@suse.com>
> Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
> ---
> include/linux/vmalloc.h | 6 +++++-
> mm/vmalloc.c | 34 +++++++++++++++++++++++++++++++---
> 2 files changed, 36 insertions(+), 4 deletions(-)
Reviewed-by: Baoquan He <bhe@redhat.com>
>
> diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h
> index 2759dac6be44..97252078a3dc 100644
> --- a/include/linux/vmalloc.h
> +++ b/include/linux/vmalloc.h
> @@ -50,7 +50,11 @@ struct iov_iter; /* in uio.h */
> #endif
>
> struct vm_struct {
> - struct vm_struct *next;
> + union {
> + struct vm_struct *next; /* Early registration of vm_areas. */
> + struct llist_node llnode; /* Asynchronous freeing on error paths. */
> + };
> +
> void *addr;
> unsigned long size;
> unsigned long flags;
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index b77e8be75f10..e61e62872372 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -3686,6 +3686,35 @@ vm_area_alloc_pages(gfp_t gfp, int nid,
> return nr_allocated;
> }
>
> +static LLIST_HEAD(pending_vm_area_cleanup);
> +static void cleanup_vm_area_work(struct work_struct *work)
> +{
> + struct vm_struct *area, *tmp;
> + struct llist_node *head;
> +
> + head = llist_del_all(&pending_vm_area_cleanup);
> + if (!head)
> + return;
> +
> + llist_for_each_entry_safe(area, tmp, head, llnode) {
> + if (!area->pages)
> + free_vm_area(area);
> + else
> + vfree(area->addr);
> + }
> +}
> +
> +/*
> + * Helper for __vmalloc_area_node() to defer cleanup
> + * of partially initialized vm_struct in error paths.
> + */
> +static DECLARE_WORK(cleanup_vm_area, cleanup_vm_area_work);
> +static void defer_vm_area_cleanup(struct vm_struct *area)
> +{
> + if (llist_add(&area->llnode, &pending_vm_area_cleanup))
> + schedule_work(&cleanup_vm_area);
> +}
> +
> static void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask,
> pgprot_t prot, unsigned int page_shift,
> int node)
> @@ -3717,8 +3746,7 @@ static void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask,
> warn_alloc(gfp_mask, NULL,
> "vmalloc error: size %lu, failed to allocated page array size %lu",
> nr_small_pages * PAGE_SIZE, array_size);
> - free_vm_area(area);
> - return NULL;
> + goto fail;
> }
>
> set_vm_area_page_order(area, page_shift - PAGE_SHIFT);
> @@ -3795,7 +3823,7 @@ static void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask,
> return area->addr;
>
> fail:
> - vfree(area->addr);
> + defer_vm_area_cleanup(area);
> return NULL;
> }
>
> --
> 2.47.3
>