Re: Occasional memory fault in inode_has_perm() while running xfstest 234

[Christoph Hellwig <hch@infradead.org>]

This looks like a selinux issues.  Ccing the LSM list.

On Thu, Nov 10, 2011 at 03:36:43PM -0600, Chandra Seetharaman wrote:
> Hi All,
> 
> While debugging the xfstest case 234, I was occasionally hitting the
> following memory fault. Has anybody seen it ?
> 
> -----------------
> IP: [<ffffffff811e57ff>] inode_has_perm+0x1f/0x40
> PGD 0 
> Oops: 0000 [#1] SMP 
> CPU 0 
> Modules linked in: xfs exportfs ebtable_nat ebtables ipt_MASQUERADE iptable_nat nf_nat iptable_mangle bridge stp llc autofs4 sunrpc cpufreq_ondemand acpi_cpufreq freq_table mperf ipt_REJECT nf_conntrack_ipv4 nf_defrag_ipv4 iptable_filter ip_tables ip6t_REJECT nf_conntrack_ipv6 nf_defrag_ipv6 xt_state nf_conntrack ip6table_filter ip6_tables ipv6 ext3 jbd dm_mirror dm_region_hash dm_log dm_mod vhost_net macvtap macvlan tun kvm_intel kvm cdc_ether usbnet mii microcode serio_raw i2c_i801 i2c_core iTCO_wdt iTCO_vendor_support shpchp ioatdma i7core_edac edac_core ses enclosure sg igb dca ext4 mbcache jbd2 sd_mod crc_t10dif ahci libahci megaraid_sas [last unloaded: scsi_wait_scan]
> 
> Pid: 32611, comm: setquota Not tainted 3.1.0-rc9.virgin+ #6 IBM  System x3630 M3 -[7377AC1]-/69Y1101     
> RIP: 0010:[<ffffffff811e57ff>]  [<ffffffff811e57ff>] inode_has_perm+0x1f/0x40
> RSP: 0018:ffff880642bcdb78  EFLAGS: 00010246
> RAX: 0000000000800002 RBX: ffff88064f2205f8 RCX: 0000000000800000
> RDX: 0000000000800000 RSI: 0000000000000000 RDI: ffff880649e58480
> RBP: ffff880642bcdb78 R08: ffff880642bcdb88 R09: 0000000000000080
> R10: ffff880658ffff00 R11: ffff880642bcdb88 R12: 0000000000000081
> R13: ffff88064f2205f8 R14: ffff8806592b8100 R15: 0000000000000000
> FS:  00007f56dfa3a700(0000) GS:ffff88067f200000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
> CR2: 0000000000000020 CR3: 0000000642b30000 CR4: 00000000000006f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
> Process setquota (pid: 32611, threadinfo ffff880642bcc000, task ffff8806592b8100)
> Stack:
> ffff880642bcdc18 ffffffff811e5d79 0000000000000009 0000000000000000
> ffff88064f2205f8 0000000000000000 0000000000000000 0000000000000000
> 0000000000000000 0000000000000000 0000000000000000 0000000000000000
> Call Trace:
> [<ffffffff811e5d79>] selinux_inode_permission+0xa9/0x100
> [<ffffffff811e323c>] security_inode_permission+0x1c/0x30
> [<ffffffff81162509>] inode_permission+0x49/0x100
> [<ffffffff81164b57>] link_path_walk+0x87/0x810
> [<ffffffff810fedfa>] ? unlock_page+0x2a/0x40
> [<ffffffff81165955>] path_lookupat+0x55/0x690
> [<ffffffff81125867>] ? handle_pte_fault+0xf7/0xb50
> [<ffffffff81165fc1>] do_path_lookup+0x31/0xc0
> [<ffffffff81162168>] ? getname_flags+0x1f8/0x280
> [<ffffffff81166df9>] user_path_at+0x59/0xa0
> [<ffffffff8112641b>] ? handle_mm_fault+0x15b/0x270
> [<ffffffff814af8c0>] ? do_page_fault+0x1e0/0x460
> [<ffffffff81146a62>] ? kmem_cache_alloc+0x152/0x190
> [<ffffffff8115b9c7>] vfs_fstatat+0x47/0x80
> [<ffffffff81077571>] ? do_sigaction+0x91/0x1d0
> [<ffffffff8115badb>] vfs_stat+0x1b/0x20
> [<ffffffff8115bb04>] sys_newstat+0x24/0x50
> [<ffffffff810c3c4f>] ? audit_syscall_entry+0x1bf/0x1f0
> [<ffffffff814b29c2>] system_call_fastpath+0x16/0x1b
> Code: 66 66 66 2e 0f 1f 84 00 00 00 00 00 55 48 89 e5 66 66 66 66 90 f6 46 0d 02 75 23 48 8b 76 38 48 8b 7f 68 45 89 c1 49 89 c8 89 d1 <0f> b7 46 20 8b 7f 04 8b 76 1c 89 c2 e8 a0 f9 ff ff c9 c3 31 c0 
> RIP  [<ffffffff811e57ff>] inode_has_perm+0x1f/0x40
> RSP <ffff880642bcdb78>
> CR2: 0000000000000020
> ---[ end trace 5d054c892d311b3f ]---
> ----------------------------
> 
> I made some code changes and found that inode->i_security is the data
> structure that is NULL.
> 
> I added the following code
> ------------------
> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
> index 266a229..43870ec 100644
> --- a/security/selinux/hooks.c
> +++ b/security/selinux/hooks.c
> @@ -1466,6 +1466,7 @@ static int task_has_system(struct task_struct *tsk,
>  			    SECCLASS_SYSTEM, perms, NULL);
>  }
>  
> +u64 isec_yes;
>  /* Check whether a task has a particular permission to an inode.
>     The 'adp' parameter is optional and allows other audit
>     data to be passed (e.g. the dentry). */
> @@ -1486,6 +1487,13 @@ static int inode_has_perm(const struct cred *cred,
>  	sid = cred_sid(cred);
>  	isec = inode->i_security;
>  
> +	if (isec)
> +		isec_yes++;
> +	else {
> +		printk("isec NULL; isec_yes %llu\n", isec_yes);
> +		return -EACCES;
> +	}
> +		
>  	return avc_has_perm_flags(sid, isec->sid, isec->sclass, perms, adp, flags);
>  }
>  
> --------------------------------
> 
> and this is what I see in /var/log/messages
> -----------------------------
> isec NULL; isec_yes 14345860
> isec NULL; isec_yes 102846678
> isec NULL; isec_yes 107203361
> isec NULL; isec_yes 136859591
> isec NULL; isec_yes 140941549
> isec NULL; isec_yes 168163633
> isec NULL; isec_yes 222030886
> isec NULL; isec_yes 238835570
> isec NULL; isec_yes 263587444
> isec NULL; isec_yes 280912141
> ------------------------------
> 
> Can somebody throw some light on it ?
> 
> I am using xfs.sgi.com with commit 9e4c109ac822395e0aae650e4e3c9e4903f6602f
> at the top.
> 
> Regards,
> 
> Chandra
> 
> _______________________________________________
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> xfs@oss.sgi.com
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---end quoted text---

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