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From: Devesh Sharma <Devesh.Sharma@Emulex.Com>
To: Trond Myklebust <trond.myklebust@primarydata.com>
CC: "linux-nfs@vger.kernel.org" <linux-nfs@vger.kernel.org>,
        "linux-rdma@vger.kernel.org" <linux-rdma@vger.kernel.org>
Subject: RE: [PATCH] NFS-RDMA: fix qp pointer validation checks
Date: Tue, 8 Apr 2014 02:07:47 +0000
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Yes, This is correct, I should check for a NULL pointer instead of IS_ERR(). I will send a V1 for this.

-----Original Message-----
From: Trond Myklebust [mailto:trond.myklebust@primarydata.com] 
Sent: Tuesday, April 08, 2014 5:43 AM
To: Devesh Sharma
Cc: linux-nfs@vger.kernel.org; linux-rdma@vger.kernel.org
Subject: Re: [PATCH] NFS-RDMA: fix qp pointer validation checks


On Apr 7, 2014, at 20:07, Devesh Sharma <Devesh.Sharma@Emulex.Com> wrote:

> This is the stack trace seen during one of the test cases where rdma_create_qp() made to fail deliberately and nfs-rdma client ended up in Panic. 
> 
> <3>ocrdma_mbx_create_qp(0) rq_err
> <3>ocrdma_mbx_create_qp(0) sq_err
> <3>ocrdma_create_qp(0) error=-22
> <1>BUG: unable to handle kernel NULL pointer dereference at 
> 0000000000000040
> <1>IP: [<ffffffffa0265451>] ib_destroy_qp+0x21/0x120 [ib_core] <4>PGD 
> 46427d067 PUD 456244067 PMD 0
> <4>Oops: 0000 [#1] SMP
> <4>last sysfs file: /sys/kernel/mm/ksm/run <4>CPU 8 <4>Modules linked 
> in: nfs lockd fscache auth_rpcgss nfs_acl xprtrdma(U) ocrdma(U) 
> be2net(U) ip6table_filter ip6_tables ebtable_nat ebtables 
> ipt_MASQUERADE iptable_nat nf_nat nf_conntrack_ipv4 nf_defrag_ipv4 
> xt_state nf_conntrack ipt_REJECT xt_CHECKSUM iptable_mangle 
> iptable_filter ip_tables bridge stp llc autofs4 des_generic ecb md4 
> nls_utf8 cifs sunrpc rdma_ucm(U) rdma_cm(U) iw_cm(U) ib_addr(U) 
> ib_ipoib(U) ib_cm(U) ib_sa(U) ipv6 ib_uverbs(U) ib_umad(U) iw_nes(U) 
> libcrc32c iw_cxgb4(U) cxgb4(U) iw_cxgb3(U) cxgb3(U) mdio ib_qib(U) 
> mlx4_en(U) mlx4_ib(U) mlx4_core(U) ib_mthca(U) ib_mad(U) ib_core(U) 
> compat(U) vhost_net macvtap macvlan tun kvm uinput power_meter sg 
> microcode i2c_i801 i2c_core iTCO_wdt iTCO_vendor_support igb ptp 
> pps_core ioatdma dca i7core_edac edac_core ext3 jbd mbcache sr_mod 
> cdrom sd_mod crc_t10dif usb_storage pata_acpi ata_generic ata_piix 
> mptsas mptscsih mptbase scsi_transport_sas dm_mirror dm_region_hash 
> dm_log dm_mod [last unloaded: be2net] <4>
> <4>Pid: 1697, comm: events/8 Not tainted 2.6.32-358.el6.x86_64 #1 
> Cisco Systems Inc R210-2121605W/R210-2121605W
> <4>RIP: 0010:[<ffffffffa0265451>]  [<ffffffffa0265451>] 
> ib_destroy_qp+0x21/0x120 [ib_core]

Sure, but that is a NULL pointer dereference. Why are you adding these tests for IS_ERR(), which won't catch NULL pointers, and are instead testing for conditions that can never happen?

> <4>RSP: 0018:ffff880467731cb0  EFLAGS: 00010282
> <4>RAX: ffff880467730000 RBX: ffff88046811e000 RCX: ffff88046313a040
> <4>RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
> <4>RBP: ffff880467731ce0 R08: ffff880467731c78 R09: 0000000000000000
> <4>R10: 0000000000000000 R11: 0000000000000000 R12: ffff88046811e210
> <4>R13: 0000000000000000 R14: ffff880466696400 R15: ffffe8ffffb01d08
> <4>FS:  0000000000000000(0000) GS:ffff880036900000(0000) 
> knlGS:0000000000000000
> <4>CS:  0010 DS: 0018 ES: 0018 CR0: 000000008005003b
> <4>CR2: 0000000000000040 CR3: 00000004624b8000 CR4: 00000000000007e0
> <4>DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> <4>DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 
> <4>Process events/8 (pid: 1697, threadinfo ffff880467730000, task 
> ffff88046313a040)
> <4>Stack:
> <4> ffff8804679cd5b8 ffff88046811e000 ffff88046811e210 
> 0000000000000000 <4><d> ffff880466696400 ffffe8ffffb01d08 
> ffff880467731d00 ffffffffa0588f51 <4><d> ffff8804679cd5e0 
> ffff8804679cd598 ffff880467731e10 ffffffffa02e9e75 <4>Call Trace:
> <4> [<ffffffffa0588f51>] rdma_destroy_qp+0x31/0x50 [rdma_cm] <4> 
> [<ffffffffa02e9e75>] rpcrdma_ep_connect+0x135/0x3e0 [xprtrdma] <4> 
> [<ffffffff8150d6e0>] ? thread_return+0x4e/0x76e <4> 
> [<ffffffffa05d06ae>] ? rpc_wake_up_task_queue_locked+0x18e/0x270 
> [sunrpc] <4> [<ffffffffa02e6ff0>] ? xprt_rdma_connect_worker+0x0/0xc0 
> [xprtrdma] <4> [<ffffffffa02e7032>] xprt_rdma_connect_worker+0x42/0xc0 
> [xprtrdma] <4> [<ffffffff81090ac0>] worker_thread+0x170/0x2a0 <4> 
> [<ffffffff81096c80>] ? autoremove_wake_function+0x0/0x40 <4> 
> [<ffffffff81090950>] ? worker_thread+0x0/0x2a0 <4> 
> [<ffffffff81096916>] kthread+0x96/0xa0 <4> [<ffffffff8100c0ca>] 
> child_rip+0xa/0x20 <4> [<ffffffff81096880>] ? kthread+0x0/0xa0 <4> 
> [<ffffffff8100c0c0>] ? child_rip+0x0/0x20
> <4>Code: 65 f0 4c 8b 6d f8 c9 c3 66 90 55 48 89 e5 48 83 ec 30 48 89 
> 5d d8 4c 89 65 e0 4c 89 6d e8 4c 89 75 f0 4c 89 7d f8 0f 1f 44 00 00 
> <8b> 57 40 b8 f0 ff ff ff 49 89 fe 85 d2 75 39 4c 8b 67 58 49 39 
> <1>RIP  [<ffffffffa0265451>] ib_destroy_qp+0x21/0x120 [ib_core] <4> 
> RSP <ffff880467731cb0>
> <4>CR2: 0000000000000040
> 
> -----Original Message-----
> From: Trond Myklebust [mailto:trond.myklebust@primarydata.com]
> Sent: Tuesday, April 08, 2014 5:31 AM
> To: Devesh Sharma
> Cc: linux-nfs@vger.kernel.org; linux-rdma@vger.kernel.org
> Subject: Re: [PATCH] NFS-RDMA: fix qp pointer validation checks
> 
> 
> On Apr 7, 2014, at 19:45, Devesh Sharma <Devesh.Sharma@Emulex.Com> wrote:
> 
>> Hi
>> Inline Below:
>> 
>> -----Original Message-----
>> From: Trond Myklebust [mailto:trond.myklebust@primarydata.com]
>> Sent: Tuesday, April 08, 2014 4:58 AM
>> To: Devesh Sharma
>> Cc: linux-nfs@vger.kernel.org; linux-rdma@vger.kernel.org
>> Subject: Re: [PATCH] NFS-RDMA: fix qp pointer validation checks
>> 
>> 
>> On Apr 7, 2014, at 18:30, devesh.sharma@emulex.com wrote:
>> 
>>> From: Devesh Sharma <devesh.sharma@emulex.com>
>>> 
>>> If the rdma_create_qp fails to create qp due to device firmware 
>>> being in invalid state xprtrdma still tries to destroy the 
>>> non-existant qp and ends up in a NULL pointer reference crash.
>>> Adding proper checks for vaidating QP pointer avoids this to happen.
>>> 
>> 
>> As far as I can see, rdma_create_qp() only sets id->qp on success. Otherwise it is left with the same value as it had on entry (i.e. NULL). What am I missing?
>> [DS]: If you focus on rpcrdma_ep_connect() function and assume that rdma_create_qp() has failed with some valid error code, then this callback function will return ep->rep_connected = some non-zero.
>> Eventually xprt_rdma_connect_worker() will call rpcrdma_ep_connect() 
>> again and rpcrdma_ep_connect will try to free-up all the resources, now rdma_destroy_qp() will be called with invalid QP (which is NULL) pointer And hence kernel will panic. Please correct me if I am worng.
>> 
> 
> AFAICS your patch does nothing to address that problem. Instead it adds tests for IS_ERR(ia->ri_id->qp), which can never happen because ia->ri_id->qp is either NULL or points to a valid structure.
> 
> _________________________________
> Trond Myklebust
> Linux NFS client maintainer, PrimaryData 
> trond.myklebust@primarydata.com
> 

_________________________________
Trond Myklebust
Linux NFS client maintainer, PrimaryData trond.myklebust@primarydata.com