On Sun, Oct 16, 2016 at 6:46 AM, Baozeng Ding <splovi...@gmail.com> wrote: > Hello all, > While running syzkaller fuzzer I have got the following use-after-free > bug in udp_lib_get_port. The kernel version is 4.8.0+ (on Oct 7 commit > d1f5323370fceaed43a7ee38f4c7bfc7e70f28d0). Unfortunately I failed to find a > reproducer for it. > > BUG: KASAN: use-after-free in udp_lib_get_port+0x1573/0x1860 at addr > ffff88000804cb60 > Write of size 8 by task syz-executor/31190 > CPU: 0 PID: 31190 Comm: syz-executor Not tainted 4.8.0+ #39 > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS > rel-1.8.2-0-g33fbe13 by qemu-project.org 04/01/2014 > ffff880015ac7a48 ffffffff829f835b ffff880032b531c0 ffff88000804cb40 > ffff88000804d250 ffff880017415a4a ffff880015ac7a70 ffffffff8174d3cc > ffff880015ac7b00 ffff88000804cb00 ffff880032b531c0 ffff880015ac7af0 > Call Trace: > [<ffffffff829f835b>] dump_stack+0xb3/0x118 lib/dump_stack.c:15 > [<ffffffff8174d3cc>] kasan_object_err+0x1c/0x70 mm/kasan/report.c:156 > [< inline >] print_address_description mm/kasan/report.c:194 > [<ffffffff8174d666>] kasan_report_error+0x1f6/0x4d0 mm/kasan/report.c:283 > [< inline >] kasan_report mm/kasan/report.c:303 > [<ffffffff8174db7e>] __asan_report_store8_noabort+0x3e/0x40 > mm/kasan/report.c:329 > [< inline >] hlist_add_head_rcu ./include/linux/rculist.h:487 > [<ffffffff850866e3>] udp_lib_get_port+0x1573/0x1860 net/ipv4/udp.c:345 > [<ffffffff8525cc27>] udp_v6_get_port+0xa7/0xd0 net/ipv6/udp.c:106 > [<ffffffff851df52c>] inet6_bind+0x89c/0xfb0 net/ipv6/af_inet6.c:384 > [<ffffffff84c492fa>] SYSC_bind+0x1ea/0x250 net/socket.c:1367 > [<ffffffff84c4ba34>] SyS_bind+0x24/0x30 net/socket.c:1353 > [<ffffffff85e4d685>] entry_SYSCALL_64_fastpath+0x23/0xc6
We should have a reference to this sock via fd and its sock->sk too, so I fail to see why it could be freed while we holding this reference. Maybe a VFS layer bug? > Object at ffff88000804cb40, in cache UDPv6 size: 1496 > Allocated: > PID = 30789 > [ 378.305168] [<ffffffff811ddcb6>] save_stack_trace+0x16/0x20 > [ 378.305168] [<ffffffff8174c736>] save_stack+0x46/0xd0 > [ 378.305168] [<ffffffff8174c9ad>] kasan_kmalloc+0xad/0xe0 > [ 378.305168] [<ffffffff8174cee2>] kasan_slab_alloc+0x12/0x20 > [ 378.305168] [< inline >] slab_post_alloc_hook mm/slab.h:417 > [ 378.305168] [< inline >] slab_alloc_node mm/slub.c:2708 > [ 378.305168] [< inline >] slab_alloc mm/slub.c:2716 > [ 378.305168] [<ffffffff817476a8>] kmem_cache_alloc+0xc8/0x2b0 > mm/slub.c:2721 > [ 378.305168] [<ffffffff84c4f6a9>] sk_prot_alloc+0x69/0x2b0 > net/core/sock.c:1326 > [ 378.305168] [<ffffffff84c58ac8>] sk_alloc+0x38/0xae0 net/core/sock.c:1388 > [ 378.305168] [<ffffffff851ddf67>] inet6_create+0x2d7/0x1000 > net/ipv6/af_inet6.c:182 > [ 378.305168] [<ffffffff84c4af7b>] __sock_create+0x37b/0x640 > net/socket.c:1153 > [ 378.305168] [< inline >] sock_create net/socket.c:1193 > [ 378.305168] [< inline >] SYSC_socket net/socket.c:1223 > [ 378.305168] [<ffffffff84c4b46f>] SyS_socket+0xef/0x1b0 net/socket.c:1203 > [ 378.305168] [<ffffffff85e4d685>] entry_SYSCALL_64_fastpath+0x23/0xc6 > Freed: > PID = 30789 > [ 378.305168] [<ffffffff811ddcb6>] save_stack_trace+0x16/0x20 > [ 378.305168] [<ffffffff8174c736>] save_stack+0x46/0xd0 > [ 378.305168] [<ffffffff8174cf61>] kasan_slab_free+0x71/0xb0 > [ 378.305168] [< inline >] slab_free_hook mm/slub.c:1352 > [ 378.305168] [< inline >] slab_free_freelist_hook mm/slub.c:1374 > [ 378.305168] [< inline >] slab_free mm/slub.c:2951 > [ 378.305168] [<ffffffff81748b28>] kmem_cache_free+0xc8/0x330 mm/slub.c:2973 > [ 378.305168] [< inline >] sk_prot_free net/core/sock.c:1369 > [ 378.305168] [<ffffffff84c541eb>] __sk_destruct+0x32b/0x4f0 > net/core/sock.c:1444 > [ 378.305168] [<ffffffff84c5aca4>] sk_destruct+0x44/0x80 > net/core/sock.c:1452 > [ 378.305168] [<ffffffff84c5ad33>] __sk_free+0x53/0x220 net/core/sock.c:1460 > [ 378.305168] [<ffffffff84c5af23>] sk_free+0x23/0x30 net/core/sock.c:1471 > [ 378.305168] [<ffffffff84c5cb6c>] sk_common_release+0x28c/0x3e0 > ./include/net/sock.h:1589 > [ 378.305168] [<ffffffff852569e5>] udp_lib_close+0x15/0x20 > ./include/net/udp.h:203 > [ 378.305168] [<ffffffff850b2dfd>] inet_release+0xed/0x1c0 > net/ipv4/af_inet.c:415 > [ 378.305168] [<ffffffff851dc5a0>] inet6_release+0x50/0x70 > net/ipv6/af_inet6.c:422 > [ 378.305168] [<ffffffff84c4581d>] sock_release+0x8d/0x1d0 net/socket.c:570 > [ 378.305168] [<ffffffff84c45976>] sock_close+0x16/0x20 net/socket.c:1017 > [ 378.305168] [<ffffffff817a108c>] __fput+0x28c/0x780 fs/file_table.c:208 > [ 378.305168] [<ffffffff817a1605>] ____fput+0x15/0x20 fs/file_table.c:244 > [ 378.305168] [<ffffffff813774f9>] task_work_run+0xf9/0x170 > [ 378.305168] [<ffffffff81324aae>] do_exit+0x85e/0x2a00 > [ 378.305168] [<ffffffff81326dc8>] do_group_exit+0x108/0x330 > [ 378.376437] [<ffffffff81348cf7>] get_signal+0x617/0x17a0 > kernel/signal.c:2307 > [ 378.376437] [<ffffffff811b49af>] do_signal+0x7f/0x18f0 > [ 378.376437] [<ffffffff810039bf>] exit_to_usermode_loop+0xbf/0x150 > arch/x86/entry/common.c:156 > [ 378.376437] [< inline >] prepare_exit_to_usermode > arch/x86/entry/common.c:190 > [ 378.376437] [<ffffffff81006060>] syscall_return_slowpath+0x1a0/0x1e0 > arch/x86/entry/common.c:259 > [ 378.376437] [<ffffffff85e4d726>] entry_SYSCALL_64_fastpath+0xc4/0xc6 > Memory state around the buggy address: > ffff88000804ca00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc > ffff88000804ca80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >>ffff88000804cb00: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb > ^ > ffff88000804cb80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb > ffff88000804cc00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb > ================================================================== > > Thanks && Best Regards, > Baozeng Ding
