* [PATCH v3 1/2] mm/vmalloc: fix vmalloc_dump_obj address alignment for last-page lookups
2026-09-24 8:51 [PATCH v3 0/2] mm/vmalloc: fix vmalloc_dump_obj VA lookup Ye Liu
@ 2026-09-24 8:51 ` Ye Liu
2026-09-24 8:51 ` [PATCH v3 2/2] mm/vmalloc: fix vmalloc_dump_obj cross-zone VA lookup Ye Liu
1 sibling, 0 replies; 3+ messages in thread
From: Ye Liu @ 2026-09-24 8:51 UTC (permalink / raw)
To: Andrew Morton, Uladzislau Rezki, Paul Walmsley, Palmer Dabbelt,
Albert Ou, Alexandre Ghiti
Cc: linux-mm, linux-kernel, linux-riscv, Ye Liu
From: Ye Liu <liuye@kylinos.cn>
vmalloc_dump_obj() uses PAGE_ALIGN() to normalize the input address
before looking it up in the per-node busy tree. PAGE_ALIGN() rounds
up, which can push an address in the last page of a vmalloc allocation
to va_end -- outside the [va_start, va_end) range that
__find_vmap_area() searches. This causes the lookup to miss the VA
and return false, degrading diagnostic output in OOM dumps and KASAN
reports to the less informative "vmalloc memory" fallback.
The upward alignment can also change the addr_to_node() mapping when
the page boundary crosses a vmap zone boundary, causing the search to
hit the wrong node entirely.
Use PAGE_ALIGN_DOWN() instead, which rounds down to the page
containing the address. This keeps the address within the VA range
and preserves the correct node mapping.
Signed-off-by: Ye Liu <liuye@kylinos.cn>
Reviewed-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
---
mm/vmalloc.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 859e6d2d57a3..df42d8a6f058 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -5277,7 +5277,7 @@ bool vmalloc_dump_obj(void *object)
unsigned long addr;
unsigned long nr_pages;
- addr = PAGE_ALIGN((unsigned long) object);
+ addr = PAGE_ALIGN_DOWN((unsigned long) object);
vn = addr_to_node(addr);
if (!spin_trylock(&vn->busy.lock))
--
2.25.1
^ permalink raw reply [flat|nested] 3+ messages in thread
* [PATCH v3 2/2] mm/vmalloc: fix vmalloc_dump_obj cross-zone VA lookup
2026-09-24 8:51 [PATCH v3 0/2] mm/vmalloc: fix vmalloc_dump_obj VA lookup Ye Liu
2026-09-24 8:51 ` [PATCH v3 1/2] mm/vmalloc: fix vmalloc_dump_obj address alignment for last-page lookups Ye Liu
@ 2026-09-24 8:51 ` Ye Liu
1 sibling, 0 replies; 3+ messages in thread
From: Ye Liu @ 2026-09-24 8:51 UTC (permalink / raw)
To: Andrew Morton, Uladzislau Rezki, Paul Walmsley, Palmer Dabbelt,
Albert Ou, Alexandre Ghiti
Cc: linux-mm, linux-kernel, linux-riscv, Ye Liu
From: Ye Liu <liuye@kylinos.cn>
vmalloc_dump_obj() searches only one vmap node (addr_to_node(addr)),
but a vmalloc allocation may span multiple vmap zones. The VA is
stored in only one node's rb-tree (addr_to_node(va_start)), so an
object pointer in a different zone than va_start maps to a different
node and the search misses. This affects any allocation larger than
vmap_zone_size (64 KiB) on multi-CPU systems.
Extract find_vmap_area_lock() from find_vmap_area() to share the
cross-node iteration logic. The helper supports both spin_lock and
spin_trylock, the latter for atomic dump contexts (OOM, KASAN, RCU).
Signed-off-by: Ye Liu <liuye@kylinos.cn>
---
mm/vmalloc.c | 111 +++++++++++++++++++++++++++++++++++++----------------------
1 file changed, 69 insertions(+), 42 deletions(-)
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index df42d8a6f058..e5b465de1559 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -2517,39 +2517,81 @@ static void free_unmap_vmap_area(struct vmap_area *va)
free_vmap_area_noflush(va);
}
-struct vmap_area *find_vmap_area(unsigned long addr)
+static inline int next_vmap_node_id(int i)
+{
+ return (i + nr_vmap_nodes - 1) % nr_vmap_nodes;
+}
+
+enum vmap_lock_mode {
+ VMAP_LOCK,
+ VMAP_TRYLOCK,
+};
+
+/*
+ * Search for a vmap_area at @addr across all vmap nodes. An
+ * addr_to_node_id(addr) converts an address to a node index where
+ * a VA is located. If VA spans several zones and passed addr is not
+ * the same as va->va_start, what is not common, we may need to scan
+ * extra nodes. See an example:
+ *
+ * <----va---->
+ * -|-----|-----|-----|-----|-
+ * 1 2 0 1
+ *
+ * VA resides in node 1 whereas it spans 1, 2 an 0. If passed addr
+ * is within 2 or 0 nodes we should do extra work.
+ *
+ * Returns the VA with @locked_vn->busy.lock held; the caller must
+ * release it. If @mode is VMAP_TRYLOCK, nodes that cannot be locked
+ * are skipped.
+ */
+static struct vmap_area *
+find_vmap_area_lock(unsigned long addr, struct vmap_node **locked_vn,
+ enum vmap_lock_mode mode)
{
struct vmap_node *vn;
struct vmap_area *va;
int i, j;
- if (unlikely(!vmap_initialized))
+ if (unlikely(!vmap_initialized)) {
+ *locked_vn = NULL;
return NULL;
+ }
- /*
- * An addr_to_node_id(addr) converts an address to a node index
- * where a VA is located. If VA spans several zones and passed
- * addr is not the same as va->va_start, what is not common, we
- * may need to scan extra nodes. See an example:
- *
- * <----va---->
- * -|-----|-----|-----|-----|-
- * 1 2 0 1
- *
- * VA resides in node 1 whereas it spans 1, 2 an 0. If passed
- * addr is within 2 or 0 nodes we should do extra work.
- */
i = j = addr_to_node_id(addr);
do {
vn = &vmap_nodes[i];
- spin_lock(&vn->busy.lock);
+ if (mode == VMAP_LOCK) {
+ spin_lock(&vn->busy.lock);
+ } else {
+ if (!spin_trylock(&vn->busy.lock))
+ continue;
+ }
+
va = __find_vmap_area(addr, &vn->busy.root);
+ if (va) {
+ *locked_vn = vn;
+ return va;
+ }
+
spin_unlock(&vn->busy.lock);
+ } while ((i = next_vmap_node_id(i)) != j);
- if (va)
- return va;
- } while ((i = (i + nr_vmap_nodes - 1) % nr_vmap_nodes) != j);
+ *locked_vn = NULL;
+ return NULL;
+}
+
+struct vmap_area *find_vmap_area(unsigned long addr)
+{
+ struct vmap_node *vn;
+ struct vmap_area *va;
+
+ va = find_vmap_area_lock(addr, &vn, VMAP_LOCK);
+ if (va) {
+ spin_unlock(&vn->busy.lock);
+ return va;
+ }
return NULL;
}
@@ -2558,26 +2600,14 @@ static struct vmap_area *find_unlink_vmap_area(unsigned long addr)
{
struct vmap_node *vn;
struct vmap_area *va;
- int i, j;
-
- /*
- * Check the comment in the find_vmap_area() about the loop.
- */
- i = j = addr_to_node_id(addr);
- do {
- vn = &vmap_nodes[i];
- spin_lock(&vn->busy.lock);
- va = __find_vmap_area(addr, &vn->busy.root);
- if (va)
- unlink_va(va, &vn->busy.root);
+ va = find_vmap_area_lock(addr, &vn, VMAP_LOCK);
+ if (va) {
+ unlink_va(va, &vn->busy.root);
spin_unlock(&vn->busy.lock);
+ }
- if (va)
- return va;
- } while ((i = (i + nr_vmap_nodes - 1) % nr_vmap_nodes) != j);
-
- return NULL;
+ return va;
}
/*** Per cpu kva allocator ***/
@@ -5278,14 +5308,11 @@ bool vmalloc_dump_obj(void *object)
unsigned long nr_pages;
addr = PAGE_ALIGN_DOWN((unsigned long) object);
- vn = addr_to_node(addr);
-
- if (!spin_trylock(&vn->busy.lock))
- return false;
- va = __find_vmap_area(addr, &vn->busy.root);
+ va = find_vmap_area_lock(addr, &vn, VMAP_TRYLOCK);
if (!va || !va->vm) {
- spin_unlock(&vn->busy.lock);
+ if (va)
+ spin_unlock(&vn->busy.lock);
return false;
}
--
2.25.1
^ permalink raw reply [flat|nested] 3+ messages in thread