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... - Eric
