On Mon, Aug 9, 2021 at 9:40 PM Shoaib Rao <rao.shoaib@xxxxxxxxxx> wrote: > > > On 8/9/21 12:21 PM, Dmitry Vyukov wrote: > > On Mon, 9 Aug 2021 at 21:16, Shoaib Rao <rao.shoaib@xxxxxxxxxx> wrote: > >> On 8/9/21 11:06 AM, Dmitry Vyukov wrote: > >>> On Mon, 9 Aug 2021 at 19:33, Shoaib Rao <rao.shoaib@xxxxxxxxxx> wrote: > >>>> This seems like a false positive. 1) The function will not sleep because > >>>> it only calls copy routine if the byte is present. 2). There is no > >>>> difference between this new call and the older calls in > >>>> unix_stream_read_generic(). > >>> Hi Shoaib, > >>> > >>> Thanks for looking into this. > >>> Do you have any ideas on how to fix this tool's false positive? Tools > >>> with false positives are order of magnitude less useful than tools w/o > >>> false positives. E.g. do we turn it off on syzbot? But I don't > >>> remember any other false positives from "sleeping function called from > >>> invalid context" checker... > >> Before we take any action I would like to understand why the tool does > >> not single out other calls to recv_actor in unix_stream_read_generic(). > >> The context in all cases is the same. I also do not understand why the > >> code would sleep, Let's assume the user provided address is bad, the > >> code will return EFAULT, it will never sleep, > > I always assumed that it's because if user pages are swapped out, it > > may need to read them back from disk. > > Page faults occur all the time, the page may not even be in the cache or > the mapping is not there (mmap), so I would not consider this a bug. The > code should complain about all other calls as they are also copying to > user pages. I must not be following some semantics for the code to be > triggered but I can not figure that out. What is the recommended > interface to do user copy from kernel? Are you aware of the difference between a mutex and a spinlock ? When copying data from/to user, you can not hold a spinlock. > > Shoaib > > > > >> if the kernel provided > >> address is bad the system will panic. The only difference I see is that > >> the new code holds 2 locks while the previous code held one lock, but > >> the locks are acquired before the call to copy. > >> > >> So please help me understand how the tool works. Even though I have > >> evaluated the code carefully, there is always a possibility that the > >> tool is correct. > >> > >> Shoaib > >> > >>> > >>> > >>>> On 8/8/21 4:38 PM, syzbot wrote: > >>>>> Hello, > >>>>> > >>>>> syzbot found the following issue on: > >>>>> > >>>>> HEAD commit: c2eecaa193ff pktgen: Remove redundant clone_skb override > >>>>> git tree: net-next > >>>>> console output: https://urldefense.com/v3/__https://syzkaller.appspot.com/x/log.txt?x=12e3a69e300000__;!!ACWV5N9M2RV99hQ!fbn9ny5Bw51Jl6yrU93iULDBXa_DPjyVIgQuZWyQbCo5IRkAzvYs6JKlPHEdQcWD$ > >>>>> kernel config: https://urldefense.com/v3/__https://syzkaller.appspot.com/x/.config?x=aba0c23f8230e048__;!!ACWV5N9M2RV99hQ!fbn9ny5Bw51Jl6yrU93iULDBXa_DPjyVIgQuZWyQbCo5IRkAzvYs6JKlPLGp1-Za$ > >>>>> dashboard link: https://urldefense.com/v3/__https://syzkaller.appspot.com/bug?extid=8760ca6c1ee783ac4abd__;!!ACWV5N9M2RV99hQ!fbn9ny5Bw51Jl6yrU93iULDBXa_DPjyVIgQuZWyQbCo5IRkAzvYs6JKlPCORTNOH$ > >>>>> compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.1 > >>>>> syz repro: https://urldefense.com/v3/__https://syzkaller.appspot.com/x/repro.syz?x=15c5b104300000__;!!ACWV5N9M2RV99hQ!fbn9ny5Bw51Jl6yrU93iULDBXa_DPjyVIgQuZWyQbCo5IRkAzvYs6JKlPAjhi2yc$ > >>>>> C reproducer: https://urldefense.com/v3/__https://syzkaller.appspot.com/x/repro.c?x=10062aaa300000__;!!ACWV5N9M2RV99hQ!fbn9ny5Bw51Jl6yrU93iULDBXa_DPjyVIgQuZWyQbCo5IRkAzvYs6JKlPNzAjzQJ$ > >>>>> > >>>>> The issue was bisected to: > >>>>> > >>>>> commit 314001f0bf927015e459c9d387d62a231fe93af3 > >>>>> Author: Rao Shoaib <rao.shoaib@xxxxxxxxxx> > >>>>> Date: Sun Aug 1 07:57:07 2021 +0000 > >>>>> > >>>>> af_unix: Add OOB support > >>>>> > >>>>> bisection log: https://urldefense.com/v3/__https://syzkaller.appspot.com/x/bisect.txt?x=10765f8e300000__;!!ACWV5N9M2RV99hQ!fbn9ny5Bw51Jl6yrU93iULDBXa_DPjyVIgQuZWyQbCo5IRkAzvYs6JKlPK2iWt2r$ > >>>>> final oops: https://urldefense.com/v3/__https://syzkaller.appspot.com/x/report.txt?x=12765f8e300000__;!!ACWV5N9M2RV99hQ!fbn9ny5Bw51Jl6yrU93iULDBXa_DPjyVIgQuZWyQbCo5IRkAzvYs6JKlPKAb0dft$ > >>>>> console output: https://urldefense.com/v3/__https://syzkaller.appspot.com/x/log.txt?x=14765f8e300000__;!!ACWV5N9M2RV99hQ!fbn9ny5Bw51Jl6yrU93iULDBXa_DPjyVIgQuZWyQbCo5IRkAzvYs6JKlPNlW_w-u$ > >>>>> > >>>>> IMPORTANT: if you fix the issue, please add the following tag to the commit: > >>>>> Reported-by: syzbot+8760ca6c1ee783ac4abd@xxxxxxxxxxxxxxxxxxxxxxxxx > >>>>> Fixes: 314001f0bf92 ("af_unix: Add OOB support") > >>>>> > >>>>> BUG: sleeping function called from invalid context at lib/iov_iter.c:619 > >>>>> in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 8443, name: syz-executor700 > >>>>> 2 locks held by syz-executor700/8443: > >>>>> #0: ffff888028fa0d00 (&u->iolock){+.+.}-{3:3}, at: unix_stream_read_generic+0x16c6/0x2190 net/unix/af_unix.c:2501 > >>>>> #1: ffff888028fa0df0 (&u->lock){+.+.}-{2:2}, at: spin_lock include/linux/spinlock.h:354 [inline] > >>>>> #1: ffff888028fa0df0 (&u->lock){+.+.}-{2:2}, at: unix_stream_read_generic+0x16d0/0x2190 net/unix/af_unix.c:2502 > >>>>> Preemption disabled at: > >>>>> [<0000000000000000>] 0x0 > >>>>> CPU: 1 PID: 8443 Comm: syz-executor700 Not tainted 5.14.0-rc3-syzkaller #0 > >>>>> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 > >>>>> Call Trace: > >>>>> __dump_stack lib/dump_stack.c:88 [inline] > >>>>> dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:105 > >>>>> ___might_sleep.cold+0x1f1/0x237 kernel/sched/core.c:9154 > >>>>> __might_fault+0x6e/0x180 mm/memory.c:5258 > >>>>> _copy_to_iter+0x199/0x1600 lib/iov_iter.c:619 > >>>>> copy_to_iter include/linux/uio.h:139 [inline] > >>>>> simple_copy_to_iter+0x4c/0x70 net/core/datagram.c:519 > >>>>> __skb_datagram_iter+0x10f/0x770 net/core/datagram.c:425 > >>>>> skb_copy_datagram_iter+0x40/0x50 net/core/datagram.c:533 > >>>>> skb_copy_datagram_msg include/linux/skbuff.h:3620 [inline] > >>>>> unix_stream_read_actor+0x78/0xc0 net/unix/af_unix.c:2701 > >>>>> unix_stream_recv_urg net/unix/af_unix.c:2433 [inline] > >>>>> unix_stream_read_generic+0x17cd/0x2190 net/unix/af_unix.c:2504 > >>>>> unix_stream_recvmsg+0xb1/0xf0 net/unix/af_unix.c:2717 > >>>>> sock_recvmsg_nosec net/socket.c:944 [inline] > >>>>> sock_recvmsg net/socket.c:962 [inline] > >>>>> sock_recvmsg net/socket.c:958 [inline] > >>>>> ____sys_recvmsg+0x2c4/0x600 net/socket.c:2622 > >>>>> ___sys_recvmsg+0x127/0x200 net/socket.c:2664 > >>>>> do_recvmmsg+0x24d/0x6d0 net/socket.c:2758 > >>>>> __sys_recvmmsg net/socket.c:2837 [inline] > >>>>> __do_sys_recvmmsg net/socket.c:2860 [inline] > >>>>> __se_sys_recvmmsg net/socket.c:2853 [inline] > >>>>> __x64_sys_recvmmsg+0x20b/0x260 net/socket.c:2853 > >>>>> do_syscall_x64 arch/x86/entry/common.c:50 [inline] > >>>>> do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 > >>>>> entry_SYSCALL_64_after_hwframe+0x44/0xae > >>>>> RIP: 0033:0x43ef39 > >>>>> Code: 28 c3 e8 2a 14 00 00 66 2e 0f 1f 84 00 00 00 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 c0 ff ff ff f7 d8 64 89 01 48 > >>>>> RSP: 002b:00007ffca8776d68 EFLAGS: 00000246 ORIG_RAX: 000000000000012b > >>>>> RAX: ffffffffffffffda RBX: 0000000000400488 RCX: 000000000043ef39 > >>>>> RDX: 0000000000000700 RSI: 0000000020001140 RDI: 0000000000000004 > >>>>> RBP: 0000000000402f20 R08: 0000000000000000 R09: 0000000000400488 > >>>>> R10: 0000000000000007 R11: 0000000000000246 R12: 0000000000402fb0 > >>>>> R13: 0000000000000000 R14: 00000000004ac018 R15: 0000000000400488 > >>>>> > >>>>> ============================= > >>>>> [ BUG: Invalid wait context ] > >>>>> 5.14.0-rc3-syzkaller #0 Tainted: G W > >>>>> ----------------------------- > >>>>> syz-executor700/8443 is trying to lock: > >>>>> ffff8880212b6a28 (&mm->mmap_lock#2){++++}-{3:3}, at: __might_fault+0xa3/0x180 mm/memory.c:5260 > >>>>> other info that might help us debug this: > >>>>> context-{4:4} > >>>>> 2 locks held by syz-executor700/8443: > >>>>> #0: ffff888028fa0d00 (&u->iolock){+.+.}-{3:3}, at: unix_stream_read_generic+0x16c6/0x2190 net/unix/af_unix.c:2501 > >>>>> #1: ffff888028fa0df0 (&u->lock){+.+.}-{2:2}, at: spin_lock include/linux/spinlock.h:354 [inline] > >>>>> #1: ffff888028fa0df0 (&u->lock){+.+.}-{2:2}, at: unix_stream_read_generic+0x16d0/0x2190 net/unix/af_unix.c:2502 > >>>>> stack backtrace: > >>>>> CPU: 1 PID: 8443 Comm: syz-executor700 Tainted: G W 5.14.0-rc3-syzkaller #0 > >>>>> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 > >>>>> Call Trace: > >>>>> __dump_stack lib/dump_stack.c:88 [inline] > >>>>> dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:105 > >>>>> print_lock_invalid_wait_context kernel/locking/lockdep.c:4666 [inline] > >>>>> check_wait_context kernel/locking/lockdep.c:4727 [inline] > >>>>> __lock_acquire.cold+0x213/0x3ab kernel/locking/lockdep.c:4965 > >>>>> lock_acquire kernel/locking/lockdep.c:5625 [inline] > >>>>> lock_acquire+0x1ab/0x510 kernel/locking/lockdep.c:5590 > >>>>> __might_fault mm/memory.c:5261 [inline] > >>>>> __might_fault+0x106/0x180 mm/memory.c:5246 > >>>>> _copy_to_iter+0x199/0x1600 lib/iov_iter.c:619 > >>>>> copy_to_iter include/linux/uio.h:139 [inline] > >>>>> simple_copy_to_iter+0x4c/0x70 net/core/datagram.c:519 > >>>>> __skb_datagram_iter+0x10f/0x770 net/core/datagram.c:425 > >>>>> skb_copy_datagram_iter+0x40/0x50 net/core/datagram.c:533 > >>>>> skb_copy_datagram_msg include/linux/skbuff.h:3620 [inline] > >>>>> unix_stream_read_actor+0x78/0xc0 net/unix/af_unix.c:2701 > >>>>> unix_stream_recv_urg net/unix/af_unix.c:2433 [inline] > >>>>> unix_stream_read_generic+0x17cd/0x2190 net/unix/af_unix.c:2504 > >>>>> unix_stream_recvmsg+0xb1/0xf0 net/unix/af_unix.c:2717 > >>>>> sock_recvmsg_nosec net/socket.c:944 [inline] > >>>>> sock_recvmsg net/socket.c:962 [inline] > >>>>> sock_recvmsg net/socket.c:958 [inline] > >>>>> ____sys_recvmsg+0x2c4/0x600 net/socket.c:2622 > >>>>> ___sys_recvmsg+0x127/0x200 net/socket.c:2664 > >>>>> do_recvmmsg+0x24d/0x6d0 net/socket.c:2758 > >>>>> __sys_recvmmsg net/socket.c:2837 [inline] > >>>>> __do_sys_recvmmsg net/socket.c:2860 [inline] > >>>>> __se_sys_recvmmsg net/socket.c:2853 [inline] > >>>>> __x64_sys_recvmmsg+0x20b/0x260 net/socket.c:2853 > >>>>> do_syscall_x64 arch/x86/entry/common.c:50 [inline] > >>>>> do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 > >>>>> entry_SYSCALL_64_after_hwframe+0x44/0xae > >>>>> RIP: 0033:0x43ef39 > >>>>> Code: 28 c3 e8 2a 14 00 00 66 2e 0f 1f 84 00 00 00 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 c0 ff ff ff f7 d8 64 89 01 48 > >>>>> RSP: 002b:00007ffca8776d68 EFLAGS: 00000246 ORIG_RAX: 000000000000012b > >>>>> RAX: ffffffffffffffda RBX: 0000000000400488 RCX: 000000000043ef39 > >>>>> RDX: 0000000000000700 RSI: 0000000020001140 RDI: 0000000000000004 > >>>>> RBP: 0000000000402f20 R08: 0000000000000000 R09: 0000000000400488 > >>>>> R10: 0000000000000007 R11: 0000000000000246 R12: 0000 > >>>>> > >>>>> > >>>>> --- > >>>>> This report is generated by a bot. It may contain errors. > >>>>> See https://urldefense.com/v3/__https://goo.gl/tpsmEJ__;!!ACWV5N9M2RV99hQ!fbn9ny5Bw51Jl6yrU93iULDBXa_DPjyVIgQuZWyQbCo5IRkAzvYs6JKlPG1UhbpZ$ for more information about syzbot. > >>>>> syzbot engineers can be reached at syzkaller@xxxxxxxxxxxxxxxx. > >>>>> > >>>>> syzbot will keep track of this issue. See: > >>>>> https://urldefense.com/v3/__https://goo.gl/tpsmEJ*status__;Iw!!ACWV5N9M2RV99hQ!fbn9ny5Bw51Jl6yrU93iULDBXa_DPjyVIgQuZWyQbCo5IRkAzvYs6JKlPKlEx5v1$ for how to communicate with syzbot. > >>>>> For information about bisection process see: https://urldefense.com/v3/__https://goo.gl/tpsmEJ*bisection__;Iw!!ACWV5N9M2RV99hQ!fbn9ny5Bw51Jl6yrU93iULDBXa_DPjyVIgQuZWyQbCo5IRkAzvYs6JKlPJk7KaIr$ > >>>>> syzbot can test patches for this issue, for details see: > >>>>> https://urldefense.com/v3/__https://goo.gl/tpsmEJ*testing-patches__;Iw!!ACWV5N9M2RV99hQ!fbn9ny5Bw51Jl6yrU93iULDBXa_DPjyVIgQuZWyQbCo5IRkAzvYs6JKlPMhq2hD3$ > >>>> -- > >>>> 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@xxxxxxxxxxxxxxxx. > >>>> To view this discussion on the web visit https://urldefense.com/v3/__https://groups.google.com/d/msgid/syzkaller-bugs/0c106e6c-672f-474e-5815-97b65596139d*40oracle.com__;JQ!!ACWV5N9M2RV99hQ!fbn9ny5Bw51Jl6yrU93iULDBXa_DPjyVIgQuZWyQbCo5IRkAzvYs6JKlPHjmYAGZ$ .
