On Sat, Mar 10, 2018 at 6:08 AM, Neil Horman <nhorman@xxxxxxxxxxxxx> wrote: > On Fri, Mar 09, 2018 at 12:59:06PM -0800, syzbot wrote: >> Hello, >> >> syzbot hit the following crash on net-next commit >> fd372a7a9e5e9d8011a0222d10edd3523abcd3b1 (Thu Mar 8 19:43:48 2018 +0000) >> Merge tag 'mlx5-updates-2018-02-28-2' of >> git://git.kernel.org/pub/scm/linux/kernel/git/mellanox/linux >> >> So far this crash happened 2 times on net-next. >> C reproducer is attached. >> syzkaller reproducer is attached. >> Raw console output is attached. >> compiler: gcc (GCC) 7.1.1 20170620 >> .config is attached. >> >> IMPORTANT: if you fix the bug, please add the following tag to the commit: >> Reported-by: syzbot+a4e4112c3aff00c8cfd8@xxxxxxxxxxxxxxxxxxxxxxxxx >> It will help syzbot understand when the bug is fixed. See footer for >> details. >> If you forward the report, please keep this part and the footer. >> >> IPVS: ftp: loaded support on port[0] = 21 >> IPVS: ftp: loaded support on port[0] = 21 >> IPVS: ftp: loaded support on port[0] = 21 >> IPVS: ftp: loaded support on port[0] = 21 >> ================================================================== >> BUG: KASAN: use-after-free in sctp_association_free+0x7b7/0x930 >> net/sctp/associola.c:332 >> Read of size 8 at addr ffff8801d8006ae0 by task syzkaller914861/4202 >> >> CPU: 1 PID: 4202 Comm: syzkaller914861 Not tainted 4.16.0-rc4+ #258 >> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS >> Google 01/01/2011 >> Call Trace: >> __dump_stack lib/dump_stack.c:17 [inline] >> dump_stack+0x194/0x24d lib/dump_stack.c:53 >> print_address_description+0x73/0x250 mm/kasan/report.c:256 >> kasan_report_error mm/kasan/report.c:354 [inline] >> kasan_report+0x23c/0x360 mm/kasan/report.c:412 >> __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433 >> sctp_association_free+0x7b7/0x930 net/sctp/associola.c:332 >> sctp_sendmsg+0xc67/0x1a80 net/sctp/socket.c:2075 >> inet_sendmsg+0x11f/0x5e0 net/ipv4/af_inet.c:763 >> sock_sendmsg_nosec net/socket.c:629 [inline] >> sock_sendmsg+0xca/0x110 net/socket.c:639 >> SYSC_sendto+0x361/0x5c0 net/socket.c:1748 >> SyS_sendto+0x40/0x50 net/socket.c:1716 >> do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287 >> entry_SYSCALL_64_after_hwframe+0x42/0xb7 >> RIP: 0033:0x446d09 >> RSP: 002b:00007f5dbac21da8 EFLAGS: 00000216 ORIG_RAX: 000000000000002c >> RAX: ffffffffffffffda RBX: 00000000006e29fc RCX: 0000000000446d09 >> RDX: 0000000000000001 RSI: 0000000020000340 RDI: 0000000000000003 >> RBP: 00000000006e29f8 R08: 00000000204d9000 R09: 000000000000001c >> R10: 0000000000000000 R11: 0000000000000216 R12: 0000000000000000 >> R13: 00007fff7b26fb1f R14: 00007f5dbac229c0 R15: 00000000006e2b60 >> > I think we have a corner case with a0ff660058b88d12625a783ce9e5c1371c87951f > here. If a peeloff event happens during a wait for sendbuf space, EPIPE will be > returned, and the code path appears to call sctp_association_put twice, leading > to the use after free situation. I'll write a patch this weekend Hi, Neil, you're right. I didn't expect peeloff can be done on a NEW asoc, as peeloff needs assoc_id, which can only be set when connecting has started. But I realized that: f84af33 sctp: factor out sctp_sendmsg_to_asoc from sctp_sendmsg moved sctp_primitive_ASSOCIATE(connecting) before sctp_wait_for_sndbuf (snd buffer waiting). It means peeloff can be done on a NEW asoc. So you may want to move it back. One good thing is the fix shouldn't touch the conflict on https://lkml.org/lkml/2018/3/7/1175 We can fix it right now, I think. But pls double check it before submitting the patch. We just can't grow up that fixup for linus tree's merge. Thanks. -- To unsubscribe from this list: send the line "unsubscribe linux-sctp" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
