4:11 a.m.
On 05/29/20 - 22:04, Paolo Abeni wrote:
On Tue, 2020-05-26 at 17:28 -0700, Christoph Paasch wrote:
> And another one:
>
> [ 62.586401] ==================================================================
> [ 62.588813] BUG: KASAN: use-after-free in inet_twsk_bind_unhash+0x5f/0xe0
> [ 62.589975] Write of size 8 at addr ffff88810f155a20 by task ksoftirqd/2/21
> [ 62.591194]
> [ 62.591485] CPU: 2 PID: 21 Comm: ksoftirqd/2 Kdump: loaded Not tainted
5.7.0-rc6.mptcp #36
> [ 62.593067] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
rel-1.12.1-0-ga5cab58e9a3f-prebuilt.qemu.org 04/01/2014
> [ 62.595268] Call Trace:
> [ 62.595775] dump_stack+0x76/0xa0
> [ 62.596448] print_address_description.constprop.0+0x3a/0x60
> [ 62.600581] __kasan_report.cold+0x20/0x3b
> [ 62.602968] kasan_report+0x38/0x50
> [ 62.603561] inet_twsk_bind_unhash+0x5f/0xe0
> [ 62.604282] inet_twsk_kill+0x195/0x200
> [ 62.604945] inet_twsk_deschedule_put+0x25/0x30
> [ 62.605731] tcp_v4_rcv+0xa79/0x15e0
> [ 62.607139] ip_protocol_deliver_rcu+0x37/0x270
> [ 62.607980] ip_local_deliver_finish+0xb0/0xd0
> [ 62.608758] ip_local_deliver+0x1c9/0x1e0
> [ 62.611162] ip_sublist_rcv_finish+0x84/0xa0
> [ 62.611894] ip_sublist_rcv+0x22c/0x320
> [ 62.616143] ip_list_rcv+0x1e4/0x225
> [ 62.619427] __netif_receive_skb_list_core+0x439/0x460
> [ 62.622771] netif_receive_skb_list_internal+0x3ea/0x570
> [ 62.625320] gro_normal_list.part.0+0x14/0x50
> [ 62.626088] napi_gro_receive+0x6a/0xb0
> [ 62.626787] receive_buf+0x371/0x1d50
> [ 62.632092] virtnet_poll+0x2be/0x5b0
> [ 62.634099] net_rx_action+0x1ec/0x4c0
> [ 62.636132] __do_softirq+0xfc/0x29c
> [ 62.638180] run_ksoftirqd+0x15/0x30
> [ 62.638787] smpboot_thread_fn+0x1fc/0x380
> [ 62.642009] kthread+0x1f1/0x210
> [ 62.643478] ret_from_fork+0x35/0x40
> [ 62.644094]
> [ 62.644371] Allocated by task 1355:
> [ 62.644980] save_stack+0x1b/0x40
> [ 62.645539] __kasan_kmalloc.constprop.0+0xc2/0xd0
> [ 62.646347] kmem_cache_alloc+0xb8/0x190
> [ 62.647006] getname_flags+0x6b/0x2b0
> [ 62.647627] user_path_at_empty+0x1b/0x40
> [ 62.648306] vfs_statx+0xba/0x140
> [ 62.648875] __do_sys_newstat+0x8c/0xf0
> [ 62.649518] do_syscall_64+0xbc/0x790
> [ 62.650199] entry_SYSCALL_64_after_hwframe+0x44/0xa9
> [ 62.651091]
> [ 62.651360] Freed by task 1355:
> [ 62.651903] save_stack+0x1b/0x40
> [ 62.652460] __kasan_slab_free+0x12f/0x180
> [ 62.653147] kmem_cache_free+0x87/0x240
> [ 62.653795] filename_lookup+0x183/0x250
> [ 62.654447] vfs_statx+0xba/0x140
> [ 62.655001] __do_sys_newstat+0x8c/0xf0
> [ 62.655640] do_syscall_64+0xbc/0x790
> [ 62.656246] entry_SYSCALL_64_after_hwframe+0x44/0xa9
> [ 62.657089]
> [ 62.657351] The buggy address belongs to the object at ffff88810f155500
> which belongs to the cache names_cache of size 4096
> [ 62.659420] The buggy address is located 1312 bytes inside of
> 4096-byte region [ffff88810f155500, ffff88810f156500)
> [ 62.661358] The buggy address belongs to the page:
> [ 62.662175] page:ffffea00043c5400 refcount:1 mapcount:0 mapping:0000000000000000
index:0x0 head:ffffea00043c5400 order:3 compound_mapcount:0 compound_pincount:0
> [ 62.664523] flags: 0x8000000000010200(slab|head)
> [ 62.665342] raw: 8000000000010200 0000000000000000 0000000400000001
ffff88811ac772c0
> [ 62.666713] raw: 0000000000000000 0000000000070007 00000001ffffffff
0000000000000000
> [ 62.667984] page dumped because: kasan: bad access detected
> [ 62.668904]
> [ 62.669171] Memory state around the buggy address:
> [ 62.669975] ffff88810f155900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> [ 62.671163] ffff88810f155980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> [ 62.672363] >ffff88810f155a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
fb
> [ 62.673559] ^
> [ 62.674349] ffff88810f155a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> [ 62.675531] ffff88810f155b00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> [ 62.676723] ==================================================================
Could you please try booting with "slab_nomerge" on the kernel command
line?
Possibly kasan could track better the really relevant UAF cycle that
way.
Thanks!
Sure, will try that!
Some more info from my crash-analysis: the next-pointer in the bindhash-table
is pointing to free'd memory. That free'd memory seems to be a tcp_sock in state
CLOSED.
So, I guess the bind_node is not unlinked when a socket is being free'd. I'm
adding debugging code to see if that is true.
Christoph