Hello, On Mon, 10 Jun 2019, Eric Biggers wrote: > On Tue, May 28, 2019 at 11:28:05AM -0700, syzbot wrote: > > Hello, > > > > syzbot found the following crash on: > > > > HEAD commit: cd6c84d8 Linux 5.2-rc2 > > git tree: upstream > > console output: https://syzkaller.appspot.com/x/log.txt?x=132bd44aa00000 > > kernel config: https://syzkaller.appspot.com/x/.config?x=64479170dcaf0e11 > > dashboard link: https://syzkaller.appspot.com/bug?extid=7e2e50c8adfccd2e5041 > > compiler: gcc (GCC) 9.0.0 20181231 (experimental) > > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=114b1354a00000 > > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=14b7ad26a00000 > > > > IMPORTANT: if you fix the bug, please add the following tag to the commit: > > Reported-by: syzbot+7e2e50c8adfccd2e5041@xxxxxxxxxxxxxxxxxxxxxxxxx > > > > d started: state = MASTER, mcast_ifn = syz_tun, syncid = 0, id = 0 > > BUG: memory leak > > unreferenced object 0xffff8881206bf700 (size 32): > > comm "syz-executor761", pid 7268, jiffies 4294943441 (age 20.470s) > > hex dump (first 32 bytes): > > 00 40 7c 09 81 88 ff ff 80 45 b8 21 81 88 ff ff .@|......E.!.... > > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > > backtrace: > > [<0000000057619e23>] kmemleak_alloc_recursive > > include/linux/kmemleak.h:55 [inline] > > [<0000000057619e23>] slab_post_alloc_hook mm/slab.h:439 [inline] > > [<0000000057619e23>] slab_alloc mm/slab.c:3326 [inline] > > [<0000000057619e23>] kmem_cache_alloc_trace+0x13d/0x280 mm/slab.c:3553 > > [<0000000086ce5479>] kmalloc include/linux/slab.h:547 [inline] > > [<0000000086ce5479>] start_sync_thread+0x5d2/0xe10 > > net/netfilter/ipvs/ip_vs_sync.c:1862 > > [<000000001a9229cc>] do_ip_vs_set_ctl+0x4c5/0x780 > > net/netfilter/ipvs/ip_vs_ctl.c:2402 > > [<00000000ece457c8>] nf_sockopt net/netfilter/nf_sockopt.c:106 [inline] > > [<00000000ece457c8>] nf_setsockopt+0x4c/0x80 > > net/netfilter/nf_sockopt.c:115 > > [<00000000942f62d4>] ip_setsockopt net/ipv4/ip_sockglue.c:1258 [inline] > > [<00000000942f62d4>] ip_setsockopt+0x9b/0xb0 net/ipv4/ip_sockglue.c:1238 > > [<00000000a56a8ffd>] udp_setsockopt+0x4e/0x90 net/ipv4/udp.c:2616 > > [<00000000fa895401>] sock_common_setsockopt+0x38/0x50 > > net/core/sock.c:3130 > > [<0000000095eef4cf>] __sys_setsockopt+0x98/0x120 net/socket.c:2078 > > [<000000009747cf88>] __do_sys_setsockopt net/socket.c:2089 [inline] > > [<000000009747cf88>] __se_sys_setsockopt net/socket.c:2086 [inline] > > [<000000009747cf88>] __x64_sys_setsockopt+0x26/0x30 net/socket.c:2086 > > [<00000000ded8ba80>] do_syscall_64+0x76/0x1a0 > > arch/x86/entry/common.c:301 > > [<00000000893b4ac8>] entry_SYSCALL_64_after_hwframe+0x44/0xa9 > > > > The bug is that ownership of some memory is passed to a kthread started by > kthread_run(), but the kthread can be stopped before it actually executes the > threadfn. See the code in kernel/kthread.c: > > ret = -EINTR; > if (!test_bit(KTHREAD_SHOULD_STOP, &self->flags)) { > cgroup_kthread_ready(); > __kthread_parkme(self); > ret = threadfn(data); > } > > So, apparently the thread parameters must always be owned by the owner of the > kthread, not by the kthread itself. It seems like this would be a common > mistake in kernel code; I'm surprised this doesn't come up more... Thanks! It explains the problem. It was not obvious from the fact that only tinfo was reported as a leak, nothing for tinfo->sock. Moving sock_release to owner complicates the locking but I'll try to fix it in the following days... Regards -- Julian Anastasov <ja@xxxxxx>
