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SubjectRe: [ 92/95] NFS: Fix Oopses in nfs_lookup_revalidate and nfs4_lookup_revalidate
On 09/10/2012 04:13 AM, Ben Hutchings wrote:
> 3.2-stable review patch. If anyone has any objections, please let me know.
>
> ------------------
>
> From: Trond Myklebust <Trond.Myklebust@netapp.com>
>
> Fix the following Oops in 3.5.1:
>
> BUG: unable to handle kernel NULL pointer dereference at 0000000000000038
> IP: [<ffffffffa03789cd>] nfs_lookup_revalidate+0x2d/0x480 [nfs]
> PGD 337c63067 PUD 0
> Oops: 0000 [#1] SMP
> CPU 5
> Modules linked in: nfs fscache nfsd lockd nfs_acl auth_rpcgss sunrpc af_packet binfmt_misc cpufreq_conservative cpufreq_userspace cpufreq_powersave dm_mod acpi_cpufreq mperf coretemp gpio_ich kvm_intel joydev kvm ioatdma hid_generic igb lpc_ich i7core_edac edac_core ptp serio_raw dca pcspkr i2c_i801 mfd_core sg pps_core usbhid crc32c_intel microcode button autofs4 uhci_hcd ttm drm_kms_helper drm i2c_algo_bit sysimgblt sysfillrect syscopyarea ehci_hcd usbcore usb_common scsi_dh_rdac scsi_dh_emc scsi_dh_hp_sw scsi_dh_alua scsi_dh edd fan ata_piix thermal processor thermal_sys
>
> Pid: 30431, comm: java Not tainted 3.5.1-2-default #1 Supermicro X8DTT/X8DTT
> RIP: 0010:[<ffffffffa03789cd>] [<ffffffffa03789cd>] nfs_lookup_revalidate+0x2d/0x480 [nfs]
> RSP: 0018:ffff8801b418bd38 EFLAGS: 00010292
> RAX: 00000000fffffff6 RBX: ffff88032016d800 RCX: 0000000000000020
> RDX: ffffffff00000000 RSI: 0000000000000000 RDI: ffff8801824a7b00
> RBP: ffff8801b418bdf8 R08: 7fffff0034323030 R09: fffffffff04c03ed
> R10: ffff8801824a7b00 R11: 0000000000000002 R12: ffff8801824a7b00
> R13: ffff8801824a7b00 R14: 0000000000000000 R15: ffff8803201725d0
> FS: 00002b53a46cb700(0000) GS:ffff88033fc20000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000000000000038 CR3: 000000020a426000 CR4: 00000000000007e0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
> Process java (pid: 30431, threadinfo ffff8801b418a000, task ffff8801b5d20600)
> Stack:
> ffff8801b418be44 ffff88032016d800 ffff8801b418bdf8 0000000000000000
> ffff8801824a7b00 ffff8801b418bdd7 ffff8803201725d0 ffffffff8116a9c0
> ffff8801b5c38dc0 0000000000000007 ffff88032016d800 0000000000000000
> Call Trace:
> [<ffffffff8116a9c0>] lookup_dcache+0x80/0xe0
> [<ffffffff8116aa43>] __lookup_hash+0x23/0x90
> [<ffffffff8116b4a5>] lookup_one_len+0xc5/0x100
> [<ffffffffa03869a3>] nfs_sillyrename+0xe3/0x210 [nfs]
> [<ffffffff8116cadf>] vfs_unlink.part.25+0x7f/0xe0
> [<ffffffff8116f22c>] do_unlinkat+0x1ac/0x1d0
> [<ffffffff815717b9>] system_call_fastpath+0x16/0x1b
> [<00002b5348b5f527>] 0x2b5348b5f526
> Code: ec 38 b8 f6 ff ff ff 4c 89 64 24 18 4c 89 74 24 28 49 89 fc 48 89 5c 24 08 48 89 6c 24 10 49 89 f6 4c 89 6c 24 20 4c 89 7c 24 30 <f6> 46 38 40 0f 85 d1 00 00 00 e8 c4 c4 df e0 48 8b 58 30 49 89
> RIP [<ffffffffa03789cd>] nfs_lookup_revalidate+0x2d/0x480 [nfs]
> RSP <ffff8801b418bd38>
> CR2: 0000000000000038
> ---[ end trace 845113ed191985dd ]---
>
> This Oops affects 3.5 kernels and older, and is due to lookup_one_len()
> calling down to the dentry revalidation code with a NULL pointer
> to struct nameidata.

Hmm.. in this case which filesystem is calling nfs_lookup_revalidate()
with NULL nd?

A similar patch has already been NACKed by Trond as it could break NFS
exclusive creates. The discussion thread can be found here

http://www.spinics.net/lists/linux-nfs/msg20932.html



Thanks
Suresh



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