syzbot


KASAN: use-after-free Read in bpf_skb_change_proto

Status: fixed on 2018/07/09 18:05
Subsystems: bpf net
[Documentation on labels]
Reported-by: syzbot+b44950642a0e2890dbfc@syzkaller.appspotmail.com
Fix commit: 58990d1ff3f7 bpf: reject passing modified ctx to helper functions
First crash: 2176d, last: 2176d
Similar bugs (1)
Kernel Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-4.14 KASAN: use-after-free Read in bpf_skb_change_proto 2 1726d 1749d 0/1 auto-closed as invalid on 2019/12/31 10:54

Sample crash report:
==================================================================
BUG: KASAN: use-after-free in bpf_skb_proto_xlat net/core/filter.c:2637 [inline]
BUG: KASAN: use-after-free in ____bpf_skb_change_proto net/core/filter.c:2675 [inline]
BUG: KASAN: use-after-free in bpf_skb_change_proto+0xe37/0x1300 net/core/filter.c:2650
Read of size 2 at addr ffff88019ebc6c80 by task syz-executor1/7047

CPU: 1 PID: 7047 Comm: syz-executor1 Not tainted 4.17.0-rc7+ #38
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x1b9/0x294 lib/dump_stack.c:113
 print_address_description+0x6c/0x20b mm/kasan/report.c:256
 kasan_report_error mm/kasan/report.c:354 [inline]
 kasan_report.cold.7+0x242/0x2fe mm/kasan/report.c:412
 __asan_report_load2_noabort+0x14/0x20 mm/kasan/report.c:431
 bpf_skb_proto_xlat net/core/filter.c:2637 [inline]
 ____bpf_skb_change_proto net/core/filter.c:2675 [inline]
 bpf_skb_change_proto+0xe37/0x1300 net/core/filter.c:2650

Allocated by task 8:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:448
 set_track mm/kasan/kasan.c:460 [inline]
 kasan_kmalloc+0xc4/0xe0 mm/kasan/kasan.c:553
 kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:490
 kmem_cache_alloc+0x12e/0x760 mm/slab.c:3554
 skb_clone+0x1ed/0x4f0 net/core/skbuff.c:1282
 deliver_clone+0x45/0xc0 net/bridge/br_forward.c:123
 br_flood+0x828/0x980 net/bridge/br_forward.c:224
 br_handle_frame_finish+0x1293/0x1960 net/bridge/br_input.c:169
 br_nf_hook_thresh+0x459/0x5c0 net/bridge/br_netfilter_hooks.c:1010
 br_nf_pre_routing_finish_ipv6+0x7b4/0xee0 net/bridge/br_netfilter_ipv6.c:209
 NF_HOOK include/linux/netfilter.h:287 [inline]
 br_nf_pre_routing_ipv6+0x495/0xaa0 net/bridge/br_netfilter_ipv6.c:237
 br_nf_pre_routing+0xb1f/0x17a0 net/bridge/br_netfilter_hooks.c:493
 nf_hook_entry_hookfn include/linux/netfilter.h:119 [inline]
 nf_hook_slow+0xc2/0x1c0 net/netfilter/core.c:511
 nf_hook include/linux/netfilter.h:242 [inline]
 NF_HOOK include/linux/netfilter.h:285 [inline]
 br_handle_frame+0xbe9/0x19f0 net/bridge/br_input.c:303
 __netif_receive_skb_core+0x1414/0x3650 net/core/dev.c:4600
 __netif_receive_skb+0x2c/0x1e0 net/core/dev.c:4711
 process_backlog+0x219/0x760 net/core/dev.c:5391
 napi_poll net/core/dev.c:5789 [inline]
 net_rx_action+0x7b7/0x1930 net/core/dev.c:5855
 __do_softirq+0x2e0/0xaf5 kernel/softirq.c:285

Freed by task 8:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:448
 set_track mm/kasan/kasan.c:460 [inline]
 __kasan_slab_free+0x11a/0x170 mm/kasan/kasan.c:521
 kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528
 __cache_free mm/slab.c:3498 [inline]
 kmem_cache_free+0x86/0x2d0 mm/slab.c:3756
 kfree_skbmem+0x13c/0x210 net/core/skbuff.c:582
 __kfree_skb net/core/skbuff.c:642 [inline]
 kfree_skb+0x19d/0x560 net/core/skbuff.c:659
 ip6_mc_input+0x726/0xcd0 net/ipv6/ip6_input.c:407
 dst_input include/net/dst.h:450 [inline]
 ip6_rcv_finish+0x29c/0xa10 net/ipv6/ip6_input.c:71
 NF_HOOK include/linux/netfilter.h:287 [inline]
 ipv6_rcv+0xeb8/0x2040 net/ipv6/ip6_input.c:208
 __netif_receive_skb_core+0x2468/0x3650 net/core/dev.c:4646
 __netif_receive_skb+0x2c/0x1e0 net/core/dev.c:4711
 process_backlog+0x219/0x760 net/core/dev.c:5391
 napi_poll net/core/dev.c:5789 [inline]
 net_rx_action+0x7b7/0x1930 net/core/dev.c:5855
 __do_softirq+0x2e0/0xaf5 kernel/softirq.c:285

The buggy address belongs to the object at ffff88019ebc6c80
 which belongs to the cache skbuff_head_cache of size 232
The buggy address is located 0 bytes inside of
 232-byte region [ffff88019ebc6c80, ffff88019ebc6d68)
The buggy address belongs to the page:
page:ffffea00067af180 count:1 mapcount:0 mapping:ffff88019ebc6000 index:0xffff88019ebc6b40
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff88019ebc6000 ffff88019ebc6b40 0000000100000001
raw: ffffea0006c08c20 ffffea000764db20 ffff8801d942b840 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff88019ebc6b80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88019ebc6c00: fb fb fb fb fb fc fc fc fc fc fc fc fc fc fc fc
>ffff88019ebc6c80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                   ^
 ffff88019ebc6d00: fb fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc
 ffff88019ebc6d80: fc fc fc fc fc fc fc fc 00 00 00 00 00 00 00 00
==================================================================

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2018/06/09 16:36 bpf-next 75d4e704fa8d 866118af .config console log report ci-upstream-bpf-next-kasan-gce
* Struck through repros no longer work on HEAD.