> On Thu, May 26, 2022 at 10:18 AM zhaoyang.huang
> <zhaoyang.huang@xxxxxxxxxx> wrote:
> >
> > From: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx>
> >
> > Accessing to vb->va could be deemed as use after free when KASAN is
> > enabled like bellowing. Fix it by expanding the mutex's range.
> >
> > [ 20.232335] ==================================================================
> > [ 20.232365] BUG: KASAN: use-after-free in _vm_unmap_aliases+0x164/0x364
> > [ 20.232376] Read of size 8 at addr ffffff80d84af780 by task modprobe/300
> > [ 20.232380]
> > [ 20.232395] CPU: 5 PID: 300 Comm: modprobe Tainted: G S C O 5.4.161-android12-9-03238-gd43329d103de-ab20547 #1
> > [ 20.232401] Hardware name: Spreadtrum UMS512-1H10 SoC (DT)
> > [ 20.232407] Call trace:
> > [ 20.232419] dump_backtrace+0x0/0x2b4
> > [ 20.232428] show_stack+0x24/0x30
> > [ 20.232443] dump_stack+0x15c/0x1f4
> > [ 20.232455] print_address_description+0x88/0x568
> > [ 20.232465] __kasan_report+0x1b8/0x1dc
> > [ 20.232474] kasan_report+0x10/0x18
> > [ 20.232486] __asan_report_load8_noabort+0x1c/0x24
> > [ 20.232495] _vm_unmap_aliases+0x164/0x364
> > [ 20.232505] vm_unmap_aliases+0x20/0x28
> > [ 20.232516] change_memory_common+0x2c4/0x3ec
> > [ 20.232524] set_memory_ro+0x30/0x3c
> > [ 20.232539] module_enable_ro+0x144/0x3f0
> > [ 20.232547] load_module+0x54c0/0x8248
> > [ 20.232555] __se_sys_finit_module+0x174/0x1b0
> > [ 20.232564] __arm64_sys_finit_module+0x78/0x88
> > [ 20.232573] el0_svc_common+0x19c/0x354
> > [ 20.232581] el0_svc_handler+0x48/0x54
> > [ 20.232591] el0_svc+0x8/0xc
> > [ 20.232595]
> > [ 20.232602] Allocated by task 297:
> > [ 20.232615] __kasan_kmalloc+0x130/0x1f8
> > [ 20.232625] kasan_slab_alloc+0x14/0x1c
> > [ 20.232638] kmem_cache_alloc+0x1dc/0x394
> > [ 20.232648] alloc_vmap_area+0xb4/0x1630
> > [ 20.232657] vm_map_ram+0x3ac/0x768
> > [ 20.232671] z_erofs_decompress_generic+0x2f0/0x844
> > [ 20.232681] z_erofs_decompress+0xa8/0x594
> > [ 20.232692] z_erofs_decompress_pcluster+0xeb4/0x1458
> > [ 20.232702] z_erofs_vle_unzip_wq+0xe4/0x140
> > [ 20.232715] process_one_work+0x5c0/0x10ac
> > [ 20.232724] worker_thread+0x888/0x1128
> > [ 20.232733] kthread+0x290/0x304
> > [ 20.232744] ret_from_fork+0x10/0x18
> > [ 20.232747]
> > [ 20.232752] Freed by task 51:
> > [ 20.232762] __kasan_slab_free+0x1a0/0x270
> > [ 20.232772] kasan_slab_free+0x10/0x1c
> > [ 20.232781] slab_free_freelist_hook+0xd0/0x1ac
> > [ 20.232792] kmem_cache_free+0x110/0x368
> > [ 20.232803] __purge_vmap_area_lazy+0x524/0x13e4
> > [ 20.232813] _vm_unmap_aliases+0x290/0x364
> > [ 20.232822] __vunmap+0x45c/0x5c4
> > [ 20.232831] vfree+0x74/0x16c
> > [ 20.232841] module_memfree+0x44/0x7c
> > [ 20.232850] do_free_init+0x5c/0xac
> > [ 20.232860] process_one_work+0x5c0/0x10ac
> > [ 20.232869] worker_thread+0xb3c/0x1128
> > [ 20.232877] kthread+0x290/0x304
> > [ 20.232887] ret_from_fork+0x10/0x18
> >
> > Signed-off-by: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx>
> > ---
> > mm/vmalloc.c | 3 +--
> > 1 file changed, 1 insertion(+), 2 deletions(-)
> >
> > diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> > index d2a00ad..028d65a 100644
> > --- a/mm/vmalloc.c
> > +++ b/mm/vmalloc.c
> > @@ -2081,7 +2081,7 @@ static void _vm_unmap_aliases(unsigned long start, unsigned long end, int flush)
> > return;
> >
> > might_sleep();
> > -
> > + mutex_lock(&vmap_purge_lock);
> > for_each_possible_cpu(cpu) {
> > struct vmap_block_queue *vbq = &per_cpu(vmap_block_queue, cpu);
> > struct vmap_block *vb;
> > @@ -2106,7 +2106,6 @@ static void _vm_unmap_aliases(unsigned long start, unsigned long end, int flush)
> > rcu_read_unlock();
> > }
> >
> > - mutex_lock(&vmap_purge_lock);
> > purge_fragmented_blocks_allcpus();
> > if (!__purge_vmap_area_lazy(start, end) && flush)
> > flush_tlb_kernel_range(start, end);
> > --
> > 1.9.1
> >
>
Is it easy to reproduce? If so could you please describe the steps? As i see
the freeing of the "vb" is RCU safe whereas vb->va is not. But from the first
glance i do not see how it can accessed twice. Hm..
--
Uladzislau Rezki
