KASAN: use-after-free Read in bpf_skb_change_tail (2)

Status: public: reported C repro on 2019/08/10 10:38
Reported-by: syzbot+f271ab2c54fbb0602575@syzkaller.appspotmail.com
First crash: 2571d, last: 2566d
▶ ▼ Similar bugs (2)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-4.14 KASAN: use-after-free Read in bpf_skb_change_tail 19 1 2566d 2566d 0/1 auto-closed as invalid on 2019/12/13 14:45
android-414 KASAN: use-after-free Read in bpf_skb_change_tail 19 2 2836d 2690d 0/1 auto-closed as invalid on 2019/05/18 04:13

Sample crash report:
audit: type=1400 audit(1565882842.449:8): avc:  denied  { prog_load } for  pid=1796 comm="syz-executor124" scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=bpf permissive=1
audit: type=1400 audit(1565882842.489:9): avc:  denied  { prog_run } for  pid=1796 comm="syz-executor124" scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=bpf permissive=1
==================================================================
BUG: KASAN: use-after-free in ____bpf_skb_change_tail net/core/filter.c:2371 [inline]
BUG: KASAN: use-after-free in bpf_skb_change_tail+0xa62/0xb80 net/core/filter.c:2368
Read of size 8 at addr ffff8881d9c781d0 by task syz-executor124/1796

CPU: 0 PID: 1796 Comm: syz-executor124 Not tainted 4.14.138+ #32
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0xca/0x134 lib/dump_stack.c:53
 print_address_description+0x60/0x226 mm/kasan/report.c:187
 __kasan_report.cold+0x1a/0x41 mm/kasan/report.c:316
 ____bpf_skb_change_tail net/core/filter.c:2371 [inline]
 bpf_skb_change_tail+0xa62/0xb80 net/core/filter.c:2368
 ___bpf_prog_run+0x2478/0x5510 kernel/bpf/core.c:1033

Allocated by task 1794:
 save_stack mm/kasan/common.c:76 [inline]
 set_track mm/kasan/common.c:85 [inline]
 __kasan_kmalloc.part.0+0x53/0xc0 mm/kasan/common.c:495
 slab_post_alloc_hook mm/slab.h:439 [inline]
 slab_alloc_node mm/slub.c:2758 [inline]
 slab_alloc mm/slub.c:2766 [inline]
 kmem_cache_alloc+0xd2/0x2e0 mm/slub.c:2771
 skb_clone+0x124/0x370 net/core/skbuff.c:1282
 dev_queue_xmit_nit+0x2f3/0x970 net/core/dev.c:1943
 xmit_one net/core/dev.c:3005 [inline]
 dev_hard_start_xmit+0xa3/0x8c0 net/core/dev.c:3025
 sch_direct_xmit+0x27a/0x520 net/sched/sch_generic.c:186
 __dev_xmit_skb net/core/dev.c:3218 [inline]
 __dev_queue_xmit+0x1594/0x1d00 net/core/dev.c:3493
 neigh_hh_output include/net/neighbour.h:490 [inline]
 neigh_output include/net/neighbour.h:498 [inline]
 ip_finish_output2+0x9fe/0x12f0 net/ipv4/ip_output.c:229
 ip_finish_output+0x3be/0xc80 net/ipv4/ip_output.c:317
 NF_HOOK_COND include/linux/netfilter.h:239 [inline]
 ip_output+0x1cf/0x520 net/ipv4/ip_output.c:405
 dst_output include/net/dst.h:462 [inline]
 ip_local_out+0x98/0x170 net/ipv4/ip_output.c:124
 ip_queue_xmit+0x7ca/0x1a70 net/ipv4/ip_output.c:504
 __tcp_transmit_skb+0x18bc/0x2e20 net/ipv4/tcp_output.c:1130
 tcp_transmit_skb net/ipv4/tcp_output.c:1146 [inline]
 tcp_write_xmit+0x510/0x4680 net/ipv4/tcp_output.c:2381
 __tcp_push_pending_frames+0xa0/0x230 net/ipv4/tcp_output.c:2562
 tcp_push+0x402/0x600 net/ipv4/tcp.c:715
 tcp_sendmsg_locked+0x2684/0x31e0 net/ipv4/tcp.c:1409
 tcp_sendmsg+0x2b/0x40 net/ipv4/tcp.c:1446
 inet_sendmsg+0x15b/0x520 net/ipv4/af_inet.c:760
 sock_sendmsg_nosec net/socket.c:646 [inline]
 sock_sendmsg+0xb7/0x100 net/socket.c:656
 sock_write_iter+0x20f/0x360 net/socket.c:925
 call_write_iter include/linux/fs.h:1788 [inline]
 new_sync_write fs/read_write.c:471 [inline]
 __vfs_write+0x401/0x5a0 fs/read_write.c:484
 vfs_write+0x17f/0x4d0 fs/read_write.c:546
 SYSC_write fs/read_write.c:594 [inline]
 SyS_write+0x102/0x250 fs/read_write.c:586
 do_syscall_64+0x19b/0x520 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x42/0xb7
 0xffffffffffffffff

Freed by task 1794:
 save_stack mm/kasan/common.c:76 [inline]
 set_track mm/kasan/common.c:85 [inline]
 __kasan_slab_free+0x164/0x210 mm/kasan/common.c:457
 slab_free_hook mm/slub.c:1403 [inline]
 slab_free_freelist_hook mm/slub.c:1430 [inline]
 slab_free mm/slub.c:3005 [inline]
 kmem_cache_free+0xcb/0x340 mm/slub.c:3021
 kfree_skbmem net/core/skbuff.c:586 [inline]
 kfree_skbmem+0xa0/0x110 net/core/skbuff.c:580
 __kfree_skb net/core/skbuff.c:646 [inline]
 kfree_skb+0xeb/0x370 net/core/skbuff.c:663
 packet_rcv_spkt+0xd5/0x4d0 net/packet/af_packet.c:1888
 dev_queue_xmit_nit+0x6e1/0x970 net/core/dev.c:1975
 xmit_one net/core/dev.c:3005 [inline]
 dev_hard_start_xmit+0xa3/0x8c0 net/core/dev.c:3025
 sch_direct_xmit+0x27a/0x520 net/sched/sch_generic.c:186
 __dev_xmit_skb net/core/dev.c:3218 [inline]
 __dev_queue_xmit+0x1594/0x1d00 net/core/dev.c:3493
 neigh_hh_output include/net/neighbour.h:490 [inline]
 neigh_output include/net/neighbour.h:498 [inline]
 ip_finish_output2+0x9fe/0x12f0 net/ipv4/ip_output.c:229
 ip_finish_output+0x3be/0xc80 net/ipv4/ip_output.c:317
 NF_HOOK_COND include/linux/netfilter.h:239 [inline]
 ip_output+0x1cf/0x520 net/ipv4/ip_output.c:405
 dst_output include/net/dst.h:462 [inline]
 ip_local_out+0x98/0x170 net/ipv4/ip_output.c:124
 ip_queue_xmit+0x7ca/0x1a70 net/ipv4/ip_output.c:504
 __tcp_transmit_skb+0x18bc/0x2e20 net/ipv4/tcp_output.c:1130
 tcp_transmit_skb net/ipv4/tcp_output.c:1146 [inline]
 tcp_write_xmit+0x510/0x4680 net/ipv4/tcp_output.c:2381
 __tcp_push_pending_frames+0xa0/0x230 net/ipv4/tcp_output.c:2562
 tcp_push+0x402/0x600 net/ipv4/tcp.c:715
 tcp_sendmsg_locked+0x2684/0x31e0 net/ipv4/tcp.c:1409
 tcp_sendmsg+0x2b/0x40 net/ipv4/tcp.c:1446
 inet_sendmsg+0x15b/0x520 net/ipv4/af_inet.c:760
 sock_sendmsg_nosec net/socket.c:646 [inline]
 sock_sendmsg+0xb7/0x100 net/socket.c:656
 sock_write_iter+0x20f/0x360 net/socket.c:925
 call_write_iter include/linux/fs.h:1788 [inline]
 new_sync_write fs/read_write.c:471 [inline]
 __vfs_write+0x401/0x5a0 fs/read_write.c:484
 vfs_write+0x17f/0x4d0 fs/read_write.c:546
 SYSC_write fs/read_write.c:594 [inline]
 SyS_write+0x102/0x250 fs/read_write.c:586
 do_syscall_64+0x19b/0x520 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x42/0xb7
 0xffffffffffffffff

The buggy address belongs to the object at ffff8881d9c78140
 which belongs to the cache skbuff_head_cache of size 224
The buggy address is located 144 bytes inside of
 224-byte region [ffff8881d9c78140, ffff8881d9c78220)
The buggy address belongs to the page:
page:ffffea0007671e00 count:1 mapcount:0 mapping:          (null) index:0x0
flags: 0x4000000000000200(slab)
raw: 4000000000000200 0000000000000000 0000000000000000 00000001800c000c
raw: dead000000000100 dead000000000200 ffff8881dab70200 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8881d9c78080: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
 ffff8881d9c78100: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
>ffff8881d9c78180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                 ^
 ffff8881d9c78200: fb fb fb fb fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8881d9c78280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Crashes (3):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2019/08/15 15:30 android-4.14 0e28694fe668 0d298d6b .config console log report syz C ci-android-414-kasan-gce-root
2019/08/10 10:05 android-4.14 57ac921eaff1 acb51638 .config console log report syz C ci-android-414-kasan-gce-root
2019/08/10 09:37 android-4.14 57ac921eaff1 acb51638 .config console log report ci-android-414-kasan-gce-root
* Struck through repros no longer work on HEAD.