Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751952AbaJFTo0 (ORCPT ); Mon, 6 Oct 2014 15:44:26 -0400 Received: from static.92.5.9.176.clients.your-server.de ([176.9.5.92]:49324 "EHLO mail.hallyn.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750780AbaJFToZ (ORCPT ); Mon, 6 Oct 2014 15:44:25 -0400 Date: Mon, 6 Oct 2014 21:44:23 +0200 From: "Serge E. Hallyn" To: Andrey Wagin Cc: "Serge E. Hallyn" , linux-fsdevel@vger.kernel.org, LKML Subject: Re: BUG at /build/buildd/linux-3.13.0/fs/pnode.c:372! Message-ID: <20141006194423.GA31207@mail.hallyn.com> References: <20141006181911.GA30242@mail.hallyn.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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? > + 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/