The patch titled
Subject: mm: vmalloc: ensure vmap_block is initialised before adding to queue
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
mm-vmalloc-ensure-vmap_block-is-initialised-before-adding-to-queue.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-vmalloc-ensure-vmap_block-is-initialised-before-adding-to-queue.patch
This patch will later appear in the mm-hotfixes-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Will Deacon <will@xxxxxxxxxx>
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.
Link: https://lkml.kernel.org/r/20240812171606.17486-1-will@xxxxxxxxxx
Fixes: 8c61291fd850 ("mm: fix incorrect vbq reference in purge_fragmented_block")
Signed-off-by: Will Deacon <will@xxxxxxxxxx>
Reviewed-by: Baoquan He <bhe@xxxxxxxxxx>
Reviewed-by: Uladzislau Rezki (Sony) <urezki@xxxxxxxxx>
Cc: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx>
Cc: Hailong.Liu <hailong.liu@xxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Cc: Lorenzo Stoakes <lstoakes@xxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/vmalloc.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/mm/vmalloc.c~mm-vmalloc-ensure-vmap_block-is-initialised-before-adding-to-queue
+++ a/mm/vmalloc.c
@@ -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 will@xxxxxxxxxx are
mm-vmalloc-ensure-vmap_block-is-initialised-before-adding-to-queue.patch
