On Thu, Sep 30, 2021 at 7:06 AM Alexey Gladkov <legion@xxxxxxxxxx> wrote: > > On Wed, Sep 29, 2021 at 09:39:06PM +0000, Jordan Glover wrote: > > > I'm still investigating, but I would like to rule out one option. > > > > > > Could you check out the patch? > > > > > > Thx, I added it to my kernel and will report in few days. > > Does this patch try to fix the issue or make it easier to track? > > I suspect the error is caused by a race between allow_ucounts() and > put_ucounts(). I think this patch could solve the problem. Thanks for your help. Still can reproduce the problem with the change suggested. [ 7761.885966] ================================================================== [ 7761.893462] BUG: KASAN: use-after-free in dec_ucount+0x50/0xd8 [ 7761.899491] Write of size 8 at addr ffffff80c537b140 by task kworker/u16:3/10303 [ 7761.907110] [ 7761.908668] CPU: 0 PID: 10303 Comm: kworker/u16:3 Not tainted 5.14.0-lockdep+ #1 [ 7761.916289] Hardware name: Google Lazor (rev3+) with KB Backlight (DT) [ 7761.923021] Workqueue: netns cleanup_net [ 7761.927106] Call trace: [ 7761.929648] dump_backtrace+0x0/0x42c [ 7761.933442] show_stack+0x24/0x30 [ 7761.936878] dump_stack_lvl+0xd0/0x100 [ 7761.940763] print_address_description+0x30/0x304 [ 7761.945628] kasan_report+0x190/0x1d8 [ 7761.949418] kasan_check_range+0x1ac/0x1bc [ 7761.953655] __kasan_check_write+0x44/0x54 [ 7761.957891] dec_ucount+0x50/0xd8 [ 7761.961334] cleanup_net+0x630/0x718 [ 7761.965036] process_one_work+0x7b4/0x10ec [ 7761.969274] worker_thread+0x800/0xcf4 [ 7761.973152] kthread+0x2a8/0x358 [ 7761.976496] ret_from_fork+0x10/0x18 [ 7761.980201] [ 7761.981761] Allocated by task 4840: [ 7761.985366] kasan_save_stack+0x38/0x68 [ 7761.989342] __kasan_kmalloc+0x9c/0xb8 [ 7761.993222] kmem_cache_alloc_trace+0x2a4/0x370 [ 7761.997905] alloc_ucounts+0x150/0x374 [ 7762.001787] set_cred_ucounts+0x198/0x248 [ 7762.005935] __sys_setresuid+0x31c/0x4f8 [ 7762.009993] __arm64_sys_setresuid+0x84/0x98 [ 7762.014410] invoke_syscall+0xd4/0x2c8 [ 7762.018292] el0_svc_common+0x124/0x200 [ 7762.022265] do_el0_svc_compat+0x54/0x64 [ 7762.026325] el0_svc_compat+0x24/0x34 [ 7762.030124] el0t_32_sync_handler+0xc0/0xf0 [ 7762.034451] el0t_32_sync+0x19c/0x1a0 [ 7762.038241] [ 7762.039799] Freed by task 0: [ 7762.042778] kasan_save_stack+0x38/0x68 [ 7762.046747] kasan_set_track+0x28/0x3c [ 7762.050625] kasan_set_free_info+0x28/0x4c [ 7762.054857] ____kasan_slab_free+0x118/0x164 [ 7762.059277] __kasan_slab_free+0x18/0x28 [ 7762.063339] kfree+0x2f8/0x500 [ 7762.066505] put_ucounts+0x11c/0x134 [ 7762.070209] put_cred_rcu+0x1bc/0x35c [ 7762.074006] rcu_core+0xa68/0x1b20 [ 7762.077538] rcu_core_si+0x1c/0x28 [ 7762.081061] __do_softirq+0x4bc/0xedc [ 7762.084851] [ 7762.086401] The buggy address belongs to the object at ffffff80c537b100 [ 7762.086401] which belongs to the cache kmalloc-256 of size 256 [ 7762.099267] The buggy address is located 64 bytes inside of [ 7762.099267] 256-byte region [ffffff80c537b100, ffffff80c537b200) [ 7762.111248] The buggy address belongs to the page: [ 7762.116185] page:fffffffe0314de00 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffffff80c537ad00 pfn:0x145378 [ 7762.127180] head:fffffffe0314de00 order:3 compound_mapcount:0 compound_pincount:0 [ 7762.134881] flags: 0x8000000000010200(slab|head|zone=2) [ 7762.140286] raw: 8000000000010200 fffffffe02799408 fffffffe02020808 ffffff808000c980 [ 7762.148263] raw: ffffff80c537ad00 0000000000200004 00000001ffffffff 0000000000000000 [ 7762.156228] page dumped because: kasan: bad access detected [ 7762.161974] [ 7762.163532] Memory state around the buggy address: [ 7762.168475] ffffff80c537b000: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc [ 7762.175915] ffffff80c537b080: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc [ 7762.183346] >ffffff80c537b100: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 7762.190774] ^ [ 7762.196258] ffffff80c537b180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 7762.203689] ffffff80c537b200: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc [ 7762.211125] ==================================================================
