mm-vmalloc-ensure-vmap_block-is-initialised-before-adding-to-queue.patch removed from -mm tree

The quilt patch titled
Subject: mm: vmalloc: ensure vmap_block is initialised before adding to queue
has been removed from the -mm tree. Its filename was
mm-vmalloc-ensure-vmap_block-is-initialised-before-adding-to-queue.patch

This patch was dropped because it was merged into the mm-hotfixes-stable branch of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

------------------------------------------------------
From: Will Deacon <[email protected]>
Subject: mm: vmalloc: ensure vmap_block is initialised before adding to queue
Date: Mon, 12 Aug 2024 18:16:06 +0100

Commit 8c61291fd850 ("mm: fix incorrect vbq reference in purge_fragmented_block") extended the 'vmap_block' structure to contain a 'cpu' field which is set at allocation time to the id of the initialising CPU.

When a new 'vmap_block' is being instantiated by new_vmap_block(), the partially initialised structure is added to the local 'vmap_block_queue' xarray before the 'cpu' field has been initialised. If another CPU is concurrently walking the xarray (e.g. via vm_unmap_aliases()), then it may perform an out-of-bounds access to the remote queue thanks to an uninitialised index.

This has been observed as UBSAN errors in Android:

 | Internal error: UBSAN: array index out of bounds: 00000000f2005512 [#1] PREEMPT SMP
 |
 | Call trace:
 |  purge_fragmented_block+0x204/0x21c
 |  _vm_unmap_aliases+0x170/0x378
 |  vm_unmap_aliases+0x1c/0x28
 |  change_memory_common+0x1dc/0x26c
 |  set_memory_ro+0x18/0x24
 |  module_enable_ro+0x98/0x238
 |  do_init_module+0x1b0/0x310

Move the initialisation of 'vb->cpu' in new_vmap_block() ahead of the addition to the xarray.

---

 mm/vmalloc.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

@@ -2626,6 +2626,7 @@ static void *new_vmap_block(unsigned int
 	vb->dirty_max = 0;
 	bitmap_set(vb->used_map, 0, (1UL << order));
 	INIT_LIST_HEAD(&vb->free_list);
+	vb->cpu = raw_smp_processor_id();
 
 	xa = addr_to_vb_xa(va->va_start);
 	vb_idx = addr_to_vb_idx(va->va_start);

@@ -2642,7 +2643,6 @@ static void *new_vmap_block(unsigned int
 	 * integrity together with list_for_each_rcu from read
 	 * side.
 	 */
-	vb->cpu = raw_smp_processor_id();
 	vbq = per_cpu_ptr(&vmap_block_queue, vb->cpu);
 	spin_lock(&vbq->lock);
 	list_add_tail_rcu(&vb->free_list, &vbq->free);

_

Patches currently in -mm which might be from [email protected] are