[PATCH v4 04/10] mm/vmalloc: Defer freeing partly initialized vm_struct

Uladzislau Rezki (Sony)
2025-10-07T12:20:53Z

__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>
Reviewed-by: Baoquan He <bhe@redhat.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(-)

diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h
index eb54b7b3202f..1e43181369f1 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 d83c01caaabe..9e29dd767c41 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -3687,6 +3687,35 @@ 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)
@@ -3718,8 +3747,7 @@ 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);
@@ -3796,7 +3824,7 @@ 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