6.10-stable review patch. If anyone has any objections, please let me know.
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From: Will Deacon will@kernel.org
commit 3e3de7947c751509027d26b679ecd243bc9db255 upstream.
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@kernel.org Fixes: 8c61291fd850 ("mm: fix incorrect vbq reference in purge_fragmented_block") Signed-off-by: Will Deacon will@kernel.org Reviewed-by: Baoquan He bhe@redhat.com Reviewed-by: Uladzislau Rezki (Sony) urezki@gmail.com Cc: Zhaoyang Huang zhaoyang.huang@unisoc.com Cc: Hailong.Liu hailong.liu@oppo.com Cc: Christoph Hellwig hch@infradead.org Cc: Lorenzo Stoakes lstoakes@gmail.com Cc: Thomas Gleixner tglx@linutronix.de Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- mm/vmalloc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -2628,6 +2628,7 @@ 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); @@ -2644,7 +2645,6 @@ 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);