linux-kernel - Re: [PATCH] KEYS: fix uninitialized persistent_keyring_register

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Message-ID: <CA+5PVA6LUumBABRLcxi-Jgd+wnSt41F+7xqobPkGiYTqwBgqPw@mail.gmail.com>
Date:	Fri, 13 Dec 2013 08:37:56 -0500
From:	Josh Boyer <jwboyer@...oraproject.org>
To:	Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	David Howells <dhowells@...hat.com>,
	Serge Hallyn <serge.hallyn@...onical.com>,
	Sasha Levin <sasha.levin@...cle.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] KEYS: fix uninitialized persistent_keyring_register_sem

On Fri, Dec 13, 2013 at 2:00 AM, Xiao Guangrong
<xiaoguangrong@...ux.vnet.ibm.com> wrote:
> We run into this bug:
> [ 2736.063245] Unable to handle kernel paging request for data at address 0x00000000
> [ 2736.063293] Faulting instruction address: 0xc00000000037efb0
> [ 2736.063300] Oops: Kernel access of bad area, sig: 11 [#1]
> [ 2736.063303] SMP NR_CPUS=2048 NUMA pSeries
> [ 2736.063310] Modules linked in: sg nfsv3 rpcsec_gss_krb5 nfsv4 dns_resolver nfs fscache nf_conntrack_netbios_ns nf_conntrack_broadcast ipt_MASQUERADE ip6table_mangle ip6table_security ip6table_raw ip6t_REJECT iptable_nat nf_nat_ipv4 iptable_mangle iptable_security iptable_raw ipt_REJECT nf_conntrack_ipv4 nf_defrag_ipv4 xt_conntrack ebtable_filter ebtables ip6table_filter iptable_filter ip_tables ip6table_nat nf_conntrack_ipv6 nf_defrag_ipv6 nf_nat_ipv6 nf_nat nf_conntrack ip6_tables ibmveth pseries_rng nx_crypto nfsd auth_rpcgss nfs_acl lockd sunrpc binfmt_misc xfs libcrc32c dm_service_time sd_mod crc_t10dif crct10dif_common ibmvfc scsi_transport_fc scsi_tgt dm_mirror dm_region_hash dm_log dm_multipath dm_mod
> [ 2736.063383] CPU: 1 PID: 7128 Comm: ssh Not tainted 3.10.0-48.el7.ppc64 #1
> [ 2736.063389] task: c000000131930120 ti: c0000001319a0000 task.ti: c0000001319a0000
> [ 2736.063394] NIP: c00000000037efb0 LR: c0000000006c40f8 CTR: 0000000000000000
> [ 2736.063399] REGS: c0000001319a3870 TRAP: 0300   Not tainted  (3.10.0-48.el7.ppc64)
> [ 2736.063403] MSR: 8000000000009032 <SF,EE,ME,IR,DR,RI>  CR: 28824242  XER: 20000000
> [ 2736.063415] SOFTE: 0
> [ 2736.063418] CFAR: c00000000000908c
> [ 2736.063421] DAR: 0000000000000000, DSISR: 40000000
> [ 2736.063425]
> GPR00: c0000000006c40f8 c0000001319a3af0 c000000001074788 c0000001319a3bf0
> GPR04: 0000000000000000 0000000000000000 0000000000000020 000000000000000a
> GPR08: fffffffe00000002 00000000ffff0000 0000000080000001 c000000000924888
> GPR12: 0000000028824248 c000000007e00400 00001fffffa0f998 0000000000000000
> GPR16: 0000000000000022 00001fffffa0f998 0000010022e92470 0000000000000000
> GPR20: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
> GPR24: 0000000000000000 c000000000f4a828 00003ffffe527108 0000000000000000
> GPR28: c000000000f4a730 c000000000f4a828 0000000000000000 c0000001319a3bf0
> [ 2736.063498] NIP [c00000000037efb0] .__list_add+0x30/0x110
> [ 2736.063504] LR [c0000000006c40f8] .rwsem_down_write_failed+0x78/0x264
> [ 2736.063508] PACATMSCRATCH [800000000280f032]
> [ 2736.063511] Call Trace:
> [ 2736.063516] [c0000001319a3af0] [c0000001319a3b80] 0xc0000001319a3b80 (unreliable)
> [ 2736.063523] [c0000001319a3b80] [c0000000006c40f8] .rwsem_down_write_failed+0x78/0x264
> [ 2736.063530] [c0000001319a3c50] [c0000000006c1bb0] .down_write+0x70/0x78
> [ 2736.063536] [c0000001319a3cd0] [c0000000002e5ffc] .keyctl_get_persistent+0x20c/0x320
> [ 2736.063542] [c0000001319a3dc0] [c0000000002e2388] .SyS_keyctl+0x238/0x260
> [ 2736.063548] [c0000001319a3e30] [c000000000009e7c] syscall_exit+0x0/0x7c
> [ 2736.063553] Instruction dump:
> [ 2736.063556] 7c0802a6 fba1ffe8 fbc1fff0 fbe1fff8 7cbd2b78 7c9e2378 7c7f1b78 f8010010
> [ 2736.063566] f821ff71 e8a50008 7fa52040 40de00c0 <e8be0000> 7fbd2840 40de0094 7fbff040
> [ 2736.063579] ---[ end trace 2708241785538296 ]---
>
> It's caused by uninitialized persistent_keyring_register_sem.
>
> The bug was introduced by commit f36f8c75, two typos are in that commit:
> CONFIG_KEYS_KERBEROS_CACHE should be CONFIG_PERSISTENT_KEYRINGS and
> krb_cache_register_sem should be persistent_keyring_register_sem.
>
> Signed-off-by: Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>

Seems correct to me.  Well spotted!

Acked-by: Josh Boyer <jwboyer@...oraproject.org>

> ---
>  kernel/user.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/kernel/user.c b/kernel/user.c
> index a3a0dbf..c006131 100644
> --- a/kernel/user.c
> +++ b/kernel/user.c
> @@ -51,9 +51,9 @@ struct user_namespace init_user_ns = {
>         .owner = GLOBAL_ROOT_UID,
>         .group = GLOBAL_ROOT_GID,
>         .proc_inum = PROC_USER_INIT_INO,
> -#ifdef CONFIG_KEYS_KERBEROS_CACHE
> -       .krb_cache_register_sem =
> -       __RWSEM_INITIALIZER(init_user_ns.krb_cache_register_sem),
> +#ifdef CONFIG_PERSISTENT_KEYRINGS
> +       .persistent_keyring_register_sem =
> +       __RWSEM_INITIALIZER(init_user_ns.persistent_keyring_register_sem),
>  #endif
>  };
>  EXPORT_SYMBOL_GPL(init_user_ns);
> --
> 1.8.1.4
>
> --
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