Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751992AbaJFTvA (ORCPT ); Mon, 6 Oct 2014 15:51:00 -0400 Received: from mail-la0-f53.google.com ([209.85.215.53]:50943 "EHLO mail-la0-f53.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750909AbaJFTu7 (ORCPT ); Mon, 6 Oct 2014 15:50:59 -0400 MIME-Version: 1.0 In-Reply-To: <20141006194423.GA31207@mail.hallyn.com> References: <20141006181911.GA30242@mail.hallyn.com> <20141006194423.GA31207@mail.hallyn.com> Date: Mon, 6 Oct 2014 23:50:57 +0400 Message-ID: Subject: Re: BUG at /build/buildd/linux-3.13.0/fs/pnode.c:372! From: Andrey Wagin To: "Serge E. Hallyn" Cc: linux-fsdevel@vger.kernel.org, LKML Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 2014-10-06 23:44 GMT+04:00 Serge E. Hallyn : > Quoting Andrey Wagin (avagin@gmail.com): >> 2014-10-06 22:19 GMT+04:00 Serge E. Hallyn : >> > Quoting Andrey Wagin (avagin@gmail.com): >> >> Hi All, >> >> >> >> Here is a small program, which triggers a bug. Is it interested for someone? >> > >> > Yup, would >> > >> > diff --git a/fs/namespace.c b/fs/namespace.c >> > index ef42d9b..ddef25d 100644 >> > --- a/fs/namespace.c >> > +++ b/fs/namespace.c >> > @@ -3046,6 +3046,9 @@ static int mntns_install(struct nsproxy *nsproxy, void *ns) >> > struct mnt_namespace *mnt_ns = ns; >> > struct path root; >> > >> > + if (mnt_ns == nsproxy->mnt_ns) >> > + return 0; >> > + >> > if (!ns_capable(mnt_ns->user_ns, CAP_SYS_ADMIN) || >> > !ns_capable(current_user_ns(), CAP_SYS_CHROOT) || >> > !ns_capable(current_user_ns(), CAP_SYS_ADMIN)) >> > >> > fix it? >> >> Actually the bug is triggered from the second umount. I think we need > > Oh, I see. > >> something like this: >> diff --git a/fs/namespace.c b/fs/namespace.c >> index 68685b2..bbcd92c 100644 >> --- a/fs/namespace.c >> +++ b/fs/namespace.c >> @@ -1363,6 +1363,9 @@ static int do_umount(struct mount *mnt, int flags) >> return retval; >> } >> >> + if (mnt->mnt_parent == mnt) > > looks good (or the equivalent mnt_has_parent(mnt)). Have you tested that > this prevents your test program from causing a crash? Yes, I have. Look the strace output below. Today here is too late for sending a proper patch. > >> + return -EINVAL; >> + >> namespace_lock(); >> lock_mount_hash(); >> event++; >> >> root@ubuntu:/home/avagin# strace ./a.out >> ... >> open("/proc/self/ns/mnt", O_RDONLY) = 3 >> umount("/", MNT_DETACH) = 0 >> setns(3, 131072) = 0 >> umount("/", MNT_DETACH) = -1 EINVAL (Invalid argument) >> exit_group(0) = ? >> +++ exited with 0 +++ >> >> > >> >> root@ubuntu:/home/avagin# cat nsenter.c >> >> #define _GNU_SOURCE /* See feature_test_macros(7) */ >> >> #include >> >> #include >> >> #include >> >> #include >> >> #include >> >> #include >> >> >> >> int main(int argc, char **argv) >> >> { >> >> int fd; >> >> >> >> fd = open("/proc/self/ns/mnt", O_RDONLY); >> >> if (fd < 0) >> >> return 1; >> >> umount2("/", MNT_DETACH); >> >> if (setns(fd, CLONE_NEWNS)) >> >> return 1; >> >> umount2("/", MNT_DETACH); >> >> >> >> return 0; >> >> } >> >> >> >> root@ubuntu:/home/avagin# gcc nsenter.c -o nsenter >> >> root@ubuntu:/home/avagin# ./nsenter >> >> >> >> >> >> [ 260.548301] ------------[ cut here ]------------ >> >> [ 260.550941] kernel BUG at /build/buildd/linux-3.13.0/fs/pnode.c:372! >> >> [ 260.552068] invalid opcode: 0000 [#1] SMP >> >> [ 260.552068] Modules linked in: xt_CHECKSUM iptable_mangle xt_tcpudp >> >> xt_addrtype xt_conntrack ipt_MASQUERADE iptable_nat nf_conntrack_ipv4 >> >> nf_defrag_ipv4 nf_nat_ipv4 nf_nat nf_conntrack bridge stp llc >> >> dm_thin_pool dm_persistent_data dm_bufio dm_bio_prison iptable_filter >> >> ip_tables x_tables crct10dif_pclmul crc32_pclmul ghash_clmulni_intel >> >> binfmt_misc nfsd auth_rpcgss nfs_acl aesni_intel nfs lockd aes_x86_64 >> >> sunrpc fscache lrw gf128mul glue_helper ablk_helper cryptd serio_raw >> >> ppdev parport_pc lp parport btrfs xor raid6_pq libcrc32c psmouse >> >> floppy >> >> [ 260.552068] CPU: 0 PID: 1723 Comm: nsenter Not tainted >> >> 3.13.0-30-generic #55-Ubuntu >> >> [ 260.552068] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011 >> >> [ 260.552068] task: ffff8800376097f0 ti: ffff880074824000 task.ti: >> >> ffff880074824000 >> >> [ 260.552068] RIP: 0010:[] [] >> >> propagate_umount+0x123/0x130 >> >> [ 260.552068] RSP: 0018:ffff880074825e98 EFLAGS: 00010246 >> >> [ 260.552068] RAX: ffff88007c741140 RBX: 0000000000000002 RCX: ffff88007c741190 >> >> [ 260.552068] RDX: ffff88007c741190 RSI: ffff880074825ec0 RDI: ffff880074825ec0 >> >> [ 260.552068] RBP: ffff880074825eb0 R08: 00000000000172e0 R09: ffff88007fc172e0 >> >> [ 260.552068] R10: ffffffff811cc642 R11: ffffea0001d59000 R12: ffff88007c741140 >> >> [ 260.552068] R13: ffff88007c741140 R14: ffff88007c741140 R15: 0000000000000000 >> >> [ 260.552068] FS: 00007fd5c7e41740(0000) GS:ffff88007fc00000(0000) >> >> knlGS:0000000000000000 >> >> [ 260.552068] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 >> >> [ 260.552068] CR2: 00007fd5c7968050 CR3: 0000000070124000 CR4: 00000000000406f0 >> >> [ 260.552068] Stack: >> >> [ 260.552068] 0000000000000002 0000000000000002 ffff88007c631000 >> >> ffff880074825ed8 >> >> [ 260.552068] ffffffff811dcfac ffff88007c741140 0000000000000002 >> >> ffff88007c741160 >> >> [ 260.552068] ffff880074825f38 ffffffff811dd12b ffffffff811cc642 >> >> 0000000075640000 >> >> [ 260.552068] Call Trace: >> >> [ 260.552068] [] umount_tree+0x20c/0x260 >> >> [ 260.552068] [] do_umount+0x12b/0x300 >> >> [ 260.552068] [] ? final_putname+0x22/0x50 >> >> [ 260.552068] [] ? putname+0x29/0x40 >> >> [ 260.552068] [] SyS_umount+0xdc/0x100 >> >> [ 260.552068] [] tracesys+0xe1/0xe6 >> >> [ 260.552068] Code: 89 50 08 48 8b 50 08 48 89 02 49 89 45 08 e9 72 >> >> ff ff ff 0f 1f 44 00 00 4c 89 e6 4c 89 e7 e8 f5 f6 ff ff 48 89 c3 e9 >> >> 39 ff ff ff <0f> 0b 66 2e 0f 1f 84 00 00 00 00 00 90 66 66 66 66 90 55 >> >> b8 01 >> >> [ 260.552068] RIP [] propagate_umount+0x123/0x130 >> >> [ 260.552068] RSP >> >> [ 260.611451] ---[ end trace 11c33d85f1d4c652 ]--- >> >> -- >> >> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in >> >> the body of a message to majordomo@vger.kernel.org >> >> More majordomo info at http://vger.kernel.org/majordomo-info.html >> >> Please read the FAQ at http://www.tux.org/lkml/ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/