From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: To: dvyukov@google.com Cc: viro@zeniv.linux.org.uk, ebiederm@xmission.com, linux-fsdevel@vger.kernel.org, netdev@vger.kernel.org, linux-mm@kvack.org, syzkaller-bugs@googlegroups.com, syzbot+84371b6062cb639d797e@syzkaller.appspotmail.com Subject: Re: WARNING: refcount bug in should_fail From: Tetsuo Handa References: <001a113f6736499d1c0566363863@google.com> <201803041457.GBJ69774.OVOSOLFHQMJFFt@I-love.SAKURA.ne.jp> In-Reply-To: Message-Id: <201804012011.ABI74044.MJtOFVSHFQFOOL@I-love.SAKURA.ne.jp> Date: Sun, 1 Apr 2018 20:11:41 +0900 Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: owner-linux-mm@kvack.org List-ID: Dmitry Vyukov wrote: > On Sun, Apr 1, 2018 at 12:32 PM, Dmitry Vyukov wrote: > > On Sun, Mar 4, 2018 at 6:57 AM, Tetsuo Handa > > wrote: > >> Switching from mm to fsdevel, for this report says that put_net(net) in > >> rpc_kill_sb() made net->count < 0 when mount_ns() failed due to > >> register_shrinker() failure. > >> > >> Relevant commits will be > >> commit 9ee332d99e4d5a97 ("sget(): handle failures of register_shrinker()") and > >> commit d91ee87d8d85a080 ("vfs: Pass data, ns, and ns->userns to mount_ns."). > >> > >> When sget_userns() in mount_ns() failed, mount_ns() returns an error code to > >> the caller without calling fill_super(). That is, get_net(sb->s_fs_info) was > >> not called by rpc_fill_super() (via fill_super callback passed to mount_ns()) > >> but put_net(sb->s_fs_info) is called by rpc_kill_sb() (via fs->kill_sb() from > >> deactivate_locked_super()). > >> > >> ---------- > >> static struct dentry * > >> rpc_mount(struct file_system_type *fs_type, > >> int flags, const char *dev_name, void *data) > >> { > >> struct net *net = current->nsproxy->net_ns; > >> return mount_ns(fs_type, flags, data, net, net->user_ns, rpc_fill_super); > >> } > >> ---------- > > > > Messed kernel output, this is definitely not in should_fail. > > > > #syz dup: WARNING: refcount bug in sk_alloc > > Please don't drop reporter (syzbot) email from CC. > > #syz dup: WARNING: refcount bug in sk_alloc > Excuse me? This "refcount bug in should_fail" is talking about sget_userns() versus rpc_fill_super(). I think we need to fix either 9ee332d99e4d5a97 or d91ee87d8d85a080. > > >> syzbot wrote: > >>> Hello, > >>> > >>> syzbot hit the following crash on bpf-next commit > >>> 6f1b5a2b58d8470e5a8b25ab29f5fdb4616ffff8 (Tue Feb 27 04:11:23 2018 +0000) > >>> Merge branch 'bpf-kselftest-improvements' > >>> > >>> 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+84371b6062cb639d797e@syzkaller.appspotmail.com > >>> 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. > >>> > >>> ------------[ cut here ]------------ > >>> FAULT_INJECTION: forcing a failure. > >>> name failslab, interval 1, probability 0, space 0, times 0 > >>> refcount_t: underflow; use-after-free. > >>> CPU: 1 PID: 4239 Comm: syzkaller149381 Not tainted 4.16.0-rc2+ #20 > >>> WARNING: CPU: 0 PID: 4237 at lib/refcount.c:187 > >>> refcount_sub_and_test+0x167/0x1b0 lib/refcount.c:187 > >>> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS > >>> Google 01/01/2011 > >>> Call Trace: > >>> Kernel panic - not syncing: panic_on_warn set ... > >>> > >>> __dump_stack lib/dump_stack.c:17 [inline] > >>> dump_stack+0x194/0x24d lib/dump_stack.c:53 > >>> fail_dump lib/fault-inject.c:51 [inline] > >>> should_fail+0x8c0/0xa40 lib/fault-inject.c:149 > >>> should_failslab+0xec/0x120 mm/failslab.c:32 > >>> slab_pre_alloc_hook mm/slab.h:422 [inline] > >>> slab_alloc mm/slab.c:3365 [inline] > >>> __do_kmalloc mm/slab.c:3703 [inline] > >>> __kmalloc+0x63/0x760 mm/slab.c:3714 > >>> kmalloc include/linux/slab.h:517 [inline] > >>> kzalloc include/linux/slab.h:701 [inline] > >>> register_shrinker+0x10e/0x2d0 mm/vmscan.c:268 > >>> sget_userns+0xbbf/0xe40 fs/super.c:520 > >>> mount_ns+0x6d/0x190 fs/super.c:1029 > >>> rpc_mount+0x9e/0xd0 net/sunrpc/rpc_pipe.c:1451 > >>> mount_fs+0x66/0x2d0 fs/super.c:1222 > >>> vfs_kern_mount.part.26+0xc6/0x4a0 fs/namespace.c:1037 > >>> vfs_kern_mount fs/namespace.c:2509 [inline] > >>> do_new_mount fs/namespace.c:2512 [inline] > >>> do_mount+0xea4/0x2bb0 fs/namespace.c:2842 > >>> SYSC_mount fs/namespace.c:3058 [inline] > >>> SyS_mount+0xab/0x120 fs/namespace.c:3035 > >>> do_syscall_64+0x280/0x940 arch/x86/entry/common.c:287 > >>> entry_SYSCALL_64_after_hwframe+0x42/0xb7 > >>> RIP: 0033:0x4460f9 > >>> RSP: 002b:00007fbcd769ad78 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5 > >>> RAX: ffffffffffffffda RBX: 00000000006dcc6c RCX: 00000000004460f9 > >>> RDX: 0000000020000080 RSI: 0000000020000040 RDI: 0000000020000000 > >>> RBP: 00007fbcd769ad80 R08: 00000000200000c0 R09: 0000000000003131 > >>> R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006dcc68 > >>> R13: ffffffffffffffff R14: 0000000000000037 R15: 0030656c69662f2e > >>> CPU: 0 PID: 4237 Comm: syzkaller149381 Not tainted 4.16.0-rc2+ #20 > >>> 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 > >>> panic+0x1e4/0x41c kernel/panic.c:183 > >>> __warn+0x1dc/0x200 kernel/panic.c:547 > >>> report_bug+0x211/0x2d0 lib/bug.c:184 > >>> fixup_bug.part.11+0x37/0x80 arch/x86/kernel/traps.c:178 > >>> fixup_bug arch/x86/kernel/traps.c:247 [inline] > >>> do_error_trap+0x2d7/0x3e0 arch/x86/kernel/traps.c:296 > >>> do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:315 > >>> invalid_op+0x58/0x80 arch/x86/entry/entry_64.S:957 > >>> RIP: 0010:refcount_sub_and_test+0x167/0x1b0 lib/refcount.c:187 > >>> RSP: 0018:ffff8801b164f6d8 EFLAGS: 00010286 > >>> RAX: dffffc0000000008 RBX: 0000000000000000 RCX: ffffffff815ac30e > >>> RDX: 0000000000000000 RSI: 1ffff100362c9e8b RDI: 1ffff100362c9e60 > >>> RBP: ffff8801b164f768 R08: 0000000000000000 R09: 0000000000000000 > >>> R10: ffff8801b164f610 R11: 0000000000000000 R12: 1ffff100362c9edc > >>> R13: 00000000ffffffff R14: 0000000000000001 R15: ffff8801ae924044 > >>> refcount_dec_and_test+0x1a/0x20 lib/refcount.c:212 > >>> put_net include/net/net_namespace.h:220 [inline] > >>> rpc_kill_sb+0x253/0x3c0 net/sunrpc/rpc_pipe.c:1473 > >>> deactivate_locked_super+0x88/0xd0 fs/super.c:312 > >>> sget_userns+0xbda/0xe40 fs/super.c:522 > >>> mount_ns+0x6d/0x190 fs/super.c:1029 > >>> rpc_mount+0x9e/0xd0 net/sunrpc/rpc_pipe.c:1451 > >>> mount_fs+0x66/0x2d0 fs/super.c:1222 > >>> vfs_kern_mount.part.26+0xc6/0x4a0 fs/namespace.c:1037 > >>> vfs_kern_mount fs/namespace.c:2509 [inline] > >>> do_new_mount fs/namespace.c:2512 [inline] > >>> do_mount+0xea4/0x2bb0 fs/namespace.c:2842 > >>> SYSC_mount fs/namespace.c:3058 [inline] > >>> SyS_mount+0xab/0x120 fs/namespace.c:3035 > >>> do_syscall_64+0x280/0x940 arch/x86/entry/common.c:287 > >>> entry_SYSCALL_64_after_hwframe+0x42/0xb7 > >>> RIP: 0033:0x4460f9 > >>> RSP: 002b:00007fbcd76dcd78 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5 > >>> RAX: ffffffffffffffda RBX: 00000000006dcc3c RCX: 00000000004460f9 > >>> RDX: 0000000020000080 RSI: 0000000020000040 RDI: 0000000020000000 > >>> RBP: 00007fbcd76dcd80 R08: 00000000200000c0 R09: 0000000000003131 > >>> R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006dcc38 > >>> R13: ffffffffffffffff R14: 0000000000000028 R15: 0030656c69662f2e > >>> Dumping ftrace buffer: > >>> (ftrace buffer empty) > >>> Kernel Offset: disabled > >>> Rebooting in 86400 seconds.. > >>> > >>> > >>> --- > >>> This bug is generated by a dumb bot. It may contain errors. > >>> See https://goo.gl/tpsmEJ for details. > >>> Direct all questions to syzkaller@googlegroups.com. > >>> > >>> syzbot will keep track of this bug report. > >>> If you forgot to add the Reported-by tag, once the fix for this bug is > >>> merged > >>> into any tree, please reply to this email with: > >>> #syz fix: exact-commit-title > >>> If you want to test a patch for this bug, please reply with: > >>> #syz test: git://repo/address.git branch > >>> and provide the patch inline or as an attachment. > >>> To mark this as a duplicate of another syzbot report, please reply with: > >>> #syz dup: exact-subject-of-another-report > >>> If it's a one-off invalid bug report, please reply with: > >>> #syz invalid > >>> Note: if the crash happens again, it will cause creation of a new bug > >>> report. > >>> Note: all commands must start from beginning of the line in the email body. > >>> > >> > >> -- > >> You received this message because you are subscribed to the Google Groups "syzkaller-bugs" group. > >> To unsubscribe from this group and stop receiving emails from it, send an email to syzkaller-bugs+unsubscribe@googlegroups.com. > >> To view this discussion on the web visit https://groups.google.com/d/msgid/syzkaller-bugs/201803041457.GBJ69774.OVOSOLFHQMJFFt%40I-love.SAKURA.ne.jp. > >> For more options, visit https://groups.google.com/d/optout. >