On Tue, Jan 28, 2020 at 7:50 AM syzbot <syzbot+61cba5033e2072d61806@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote: > > syzbot has found a reproducer for the following crash on: > > HEAD commit: b0be0eff Merge tag 'x86-pti-2020-01-28' of git://git.kerne.. > git tree: upstream > console output: https://syzkaller.appspot.com/x/log.txt?x=1432aebee00000 > kernel config: https://syzkaller.appspot.com/x/.config?x=9784e57c96a92f20 > dashboard link: https://syzkaller.appspot.com/bug?extid=61cba5033e2072d61806 > compiler: gcc (GCC) 9.0.0 20181231 (experimental) > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=10088e95e00000 > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=13fa605ee00000 > > IMPORTANT: if you fix the bug, please add the following tag to the commit: > Reported-by: syzbot+61cba5033e2072d61806@xxxxxxxxxxxxxxxxxxxxxxxxx > > ===================================================== > WARNING: SOFTIRQ-safe -> SOFTIRQ-unsafe lock order detected > 5.5.0-syzkaller #0 Not tainted > ----------------------------------------------------- > syz-executor305/10624 [HC0[0]:SC0[2]:HE1:SE0] is trying to acquire: > ffff888098c14098 (&(&s->cache_lock)->rlock){+.+.}, at: spin_lock include/linux/spinlock.h:338 [inline] > ffff888098c14098 (&(&s->cache_lock)->rlock){+.+.}, at: sidtab_sid2str_put.part.0+0x36/0x880 security/selinux/ss/sidtab.c:533 > > and this task is already holding: > ffffffff89865770 (&(&nf_conntrack_locks[i])->rlock){+.-.}, at: spin_lock include/linux/spinlock.h:338 [inline] > ffffffff89865770 (&(&nf_conntrack_locks[i])->rlock){+.-.}, at: nf_conntrack_lock+0x17/0x70 net/netfilter/nf_conntrack_core.c:91 > which would create a new lock dependency: > (&(&nf_conntrack_locks[i])->rlock){+.-.} -> (&(&s->cache_lock)->rlock){+.+.} > > but this new dependency connects a SOFTIRQ-irq-safe lock: > (&(&nf_conntrack_locks[i])->rlock){+.-.} > > ... which became SOFTIRQ-irq-safe at: > lock_acquire+0x190/0x410 kernel/locking/lockdep.c:4484 > __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline] > _raw_spin_lock+0x2f/0x40 kernel/locking/spinlock.c:151 > spin_lock include/linux/spinlock.h:338 [inline] > nf_conntrack_lock+0x17/0x70 net/netfilter/nf_conntrack_core.c:91 ... > to a SOFTIRQ-irq-unsafe lock: > (&(&s->cache_lock)->rlock){+.+.} > > ... which became SOFTIRQ-irq-unsafe at: > ... > lock_acquire+0x190/0x410 kernel/locking/lockdep.c:4484 > __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline] > _raw_spin_lock+0x2f/0x40 kernel/locking/spinlock.c:151 > spin_lock include/linux/spinlock.h:338 [inline] > sidtab_sid2str_put.part.0+0x36/0x880 security/selinux/ss/sidtab.c:533 > sidtab_sid2str_put+0xa0/0xc0 security/selinux/ss/sidtab.c:566 > sidtab_entry_to_string security/selinux/ss/services.c:1279 [inline] > sidtab_entry_to_string+0xf2/0x110 security/selinux/ss/services.c:1266 > security_sid_to_context_core+0x2c6/0x3c0 security/selinux/ss/services.c:1361 > security_sid_to_context+0x34/0x40 security/selinux/ss/services.c:1384 > avc_audit_post_callback+0x102/0x790 security/selinux/avc.c:709 > common_lsm_audit+0x5ac/0x1e00 security/lsm_audit.c:466 > slow_avc_audit+0x16a/0x1f0 security/selinux/avc.c:782 > avc_audit security/selinux/include/avc.h:140 [inline] > avc_has_perm+0x543/0x610 security/selinux/avc.c:1185 > inode_has_perm+0x1a8/0x230 security/selinux/hooks.c:1631 > selinux_mmap_file+0x10a/0x1d0 security/selinux/hooks.c:3701 > security_mmap_file+0xa4/0x1e0 security/security.c:1482 > vm_mmap_pgoff+0xf0/0x230 mm/util.c:502 ... > other info that might help us debug this: > > Possible interrupt unsafe locking scenario: > > CPU0 CPU1 > ---- ---- > lock(&(&s->cache_lock)->rlock); > local_irq_disable(); > lock(&(&nf_conntrack_locks[i])->rlock); > lock(&(&s->cache_lock)->rlock); > <Interrupt> > lock(&(&nf_conntrack_locks[i])->rlock); > > *** DEADLOCK *** > > 4 locks held by syz-executor305/10624: > #0: ffffffff8c1acc68 (&table[i].mutex){+.+.}, at: nfnl_lock net/netfilter/nfnetlink.c:62 [inline] > #0: ffffffff8c1acc68 (&table[i].mutex){+.+.}, at: nfnetlink_rcv_msg+0x9ee/0xfb0 net/netfilter/nfnetlink.c:224 > #1: ffff8880836415d8 (nlk_cb_mutex-NETFILTER){+.+.}, at: netlink_dump+0xe7/0xfb0 net/netlink/af_netlink.c:2199 > #2: ffffffff89865770 (&(&nf_conntrack_locks[i])->rlock){+.-.}, at: spin_lock include/linux/spinlock.h:338 [inline] > #2: ffffffff89865770 (&(&nf_conntrack_locks[i])->rlock){+.-.}, at: nf_conntrack_lock+0x17/0x70 net/netfilter/nf_conntrack_core.c:91 > #3: ffffffff8b7df008 (&selinux_ss.policy_rwlock){.+.?}, at: security_sid_to_context_core+0x1ca/0x3c0 security/selinux/ss/services.c:1344 I think this is going to be tricky to fix due to the differing contexts from which sidtab_sid2str_put() may be called. We already have a check for !in_task() in sidtab_sid2str_put(), do we want to add a check for !in_serving_softirq() too? -- paul moore www.paul-moore.com
