On 2017-11-11 09:31 AM, Linus Torvalds wrote:
Boris Lukashev points out that Patrick should probably check a newer version of gcc.
I looked around, and in one of the emails, Patrick said:
"No changes, both the working and broken kernels were built with distro-provided gcc 5.4.0 and binutils 2.28.1"
and gcc-5.4.0 is certainly not very recent. It's not _ancient_, but it's a bug-fix release to a pretty old branch that is not exactly new.
It would probably be good to check if the problems persist with gcc 6.x or 7.x.. I have no idea which gcc version the randstruct people tend to use themselves.
I just tested it with gcc 7.2, and was able to reproduce the NULL pointer dereference, the backtrace looks slightly different this time.
I will also test with binutils 2.29, though I doubt that will make any difference.
[ 56.165181] BUG: unable to handle kernel NULL pointer dereference at 0000000000000560 [ 56.166563] IP: vfs_statfs+0x7c/0xc0 [ 56.167249] PGD 0 P4D 0 [ 56.167860] Oops: 0000 [#1] SMP [ 56.176478] Modules linked in: ipt_MASQUERADE nf_nat_masquerade_ipv4 xt_multiport xt_addrtype iptable_mangle iptable> [ 56.180227] CPU: 0 PID: 3985 Comm: nfsd Tainted: G O 4.14.0-git-kratos-1 #1 [ 56.181728] Hardware name: TYAN S5510/S5510, BIOS V2.02 03/12/2013 [ 56.182729] task: ffff88040c412a00 task.stack: ffffc90002c18000 [ 56.183629] RIP: 0010:vfs_statfs+0x7c/0xc0 [ 56.184341] RSP: 0018:ffffc90002c1bb28 EFLAGS: 00010202 [ 56.185143] RAX: 0000000000000000 RBX: ffffc90002c1bbf0 RCX: 0000000000000020 [ 56.186085] RDX: 0000000000001801 RSI: 0000000000001801 RDI: 0000000000000000 [ 56.187066] RBP: ffffc90002c1bbc0 R08: ffffffffffffff00 R09: 00000000000000ff [ 56.188268] R10: 000000000038be3a R11: ffff880408b18258 R12: 0000000000000000 [ 56.189336] R13: ffff88040c23ad00 R14: ffff88040b874000 R15: ffffc90002c1bbf0 [ 56.190444] FS: 0000000000000000(0000) GS:ffff88041fc00000(0000) knlGS:0000000000000000 [ 56.191876] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 56.192843] CR2: 0000000000000560 CR3: 0000000001e0a002 CR4: 00000000001606f0 [ 56.193898] Call Trace: [ 56.194510] nfsd4_encode_fattr+0x201/0x1f90 [ 56.195267] ? generic_permission+0x12c/0x1a0 [ 56.196025] nfsd4_encode_getattr+0x25/0x30 [ 56.196753] nfsd4_encode_operation+0x98/0x1b0 [ 56.197526] nfsd4_proc_compound+0x2a0/0x5e0 [ 56.198268] nfsd_dispatch+0xe8/0x220 [ 56.198968] svc_process_common+0x475/0x640 [ 56.199696] ? nfsd_destroy+0x60/0x60 [ 56.200404] svc_process+0xf2/0x1a0 [ 56.201079] nfsd+0xe3/0x150 [ 56.201706] kthread+0x117/0x130 [ 56.202354] ? kthread_create_on_node+0x40/0x40 [ 56.203100] ret_from_fork+0x25/0x30 [ 56.203774] Code: d6 89 d6 81 ce 00 04 00 00 f6 c1 08 0f 45 d6 89 d6 81 ce 00 08 00 00 f6 c1 10 0f 45 d6 89 d6 81 ce> [ 56.206289] RIP: vfs_statfs+0x7c/0xc0 RSP: ffffc90002c1bb28 [ 56.207110] CR2: 0000000000000560 [ 56.207763] ---[ end trace d452986a80f64aaa ]---
On Sat, Nov 11, 2017 at 8:13 AM, Kees Cook keescook@chromium.org wrote:
I'll take a closer look at this and see if I can provide something to narrow it down.