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[Sergio Gelato <Sergio.Gelato@xxxxxxxxxxx>]

I'm now testing my one-line patch from comment #5 on top of 3.2.0-67.101
(amd64, generic kernel flavour). So far it doesn't seem to make things
worse, but since I don't have a sure-fire way of triggering the bug it
may take a while to get experimental confirmation that it cures the issue.
(I'm reasonably confident about it based on my reading of the source code,
however. The various set_acl methods in 3.14 seem to be doing the
same thing as that patch.)

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https://bugs.launchpad.net/bugs/1348670

Title:
  BUG: unable to handle kernel NULL pointer dereference at
  0000000000000010, set_nfsv4_acl_one+0x21/0xb0 [nfsd]

Status in “linux” package in Ubuntu:
  Confirmed
Status in “linux” package in Debian:
  New

Bug description:
  I've seen this happen twice in the last 8 days on an NFS server
  running Ubuntu precise and kernels 3.2.0-65.98-generic (on the first
  occasion) and 3.2.0-67.101-generic (the second time), amd64. This
  never happened before in several months of operation; until 2014-07-01
  this server was running an older 3.2.0 kernel.

  When this error appears in the logs, the system stops answering NFS
  RPCs (e.g., "rpcinfo -u localhost nfs 3" hangs) and a reboot is
  necessary to restore NFS service. A more detailed stack trace follows.
  Looking at the source code (fs/nfsd/vfs.c:set_nfsv4_acl_one()) I see
  that the call posix_acl_xattr_size(pacl->a_count) is not preceded by a
  check that pacl != NULL. Could this be related to the following entry
  in the changelog for 3.2.0-65.98?

    * NFSD: Call ->set_acl with a NULL ACL structure if no entries
      - LP: #1328154

  Jul 24 10:12:53 server kernel: [575939.742131] IP: [<ffffffffa055c451>] set_nfsv4_acl_one+0x21/0xb0 [nfsd]
  Jul 24 10:12:53 server kernel: [575939.742131] PGD c243bb067 PUD c2400a067 PMD 0
  Jul 24 10:12:53 server kernel: [575939.742131] Oops: 0000 [#1] SMP
  Jul 24 10:12:53 server kernel: [575939.742131] CPU 3
  Jul 24 10:12:53 server kernel: [575939.742131] Modules linked in: usblp btrfs zlib_deflate libcrc32c ufs qnx4 hfsplus hfs minix ntfs vfat msdos fat jfs reiserfs ext2 cts openafs(P) xt_tcpudp ipmi_si ipmi_devintf ipmi_msghandler iptable_filter ip_tables x_tables autofs4 bnep parport_pc rfcomm bluetooth ppdev binfmt_misc rpcsec_gss_krb5 nfsd nfs lockd fscache auth_rpcgss nfs_acl sunrpc xfs dm_crypt bridge stp psmouse hpilo sp5100_tco i2c_piix4 amd64_edac_mod hpwdt edac_core k10temp edac_mce_amd joydev serio_raw acpi_power_meter mac_hid lp parport raid10 raid456 async_pq async_xor xor async_memcpy async_raid6_recov raid6_pq async_tx raid1 raid0 multipath linear radeon ttm drm_kms_helper drm osst usbhid hid st ch i2c_algo_bit pata_atiixp hpsa bnx2
  Jul 24 10:12:53 server kernel: [575939.742131]
  Jul 24 10:12:53 server kernel: [575939.742131] Pid: 2523, comm: nfsd Tainted: P O 3.2.0-67-generic #101-Ubuntu HP ProLiant DL385 G7
  Jul 24 10:12:53 server kernel: [575939.742131] RIP: 0010:[<ffffffffa055c451>] [<ffffffffa055c451>] set_nfsv4_acl_one+0x21/0xb0 [nfsd]
  Jul 24 10:12:53 server kernel: [575939.742131] RSP: 0018:ffff880422085ce0 EFLAGS: 00010282
  Jul 24 10:12:53 server kernel: [575939.742131] RAX: 0000000000004000 RBX: ffff880e29b16cc0 RCX: 00000000013cc2cc
  Jul 24 10:12:53 server kernel: [575939.742131] RDX: ffffffffa0583374 RSI: 0000000000000000 RDI: ffff880e29b16cc0
  Jul 24 10:12:53 server kernel: [575939.742131] RBP: ffff880422085d10 R08: ffffea002cdf3b80 R09: ffffffffa055c4af
  Jul 24 10:12:53 server kernel: [575939.742131] R10: ffff880b37ceed00 R11: 0000000040000004 R12: 0000000000000000
  Jul 24 10:12:53 server kernel: [575939.742131] R13: ffff8807f56418c0 R14: 0000000000000000 R15: ffff880c2268d180
  Jul 24 10:12:53 server kernel: [575939.742131] FS: 00007fbbbbafd700(0000) GS:ffff88103fc80000(0000) knlGS:0000000000000000
  Jul 24 10:12:53 server kernel: [575939.742131] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
  Jul 24 10:12:53 server kernel: [575939.742131] CR2: 0000000000000010 CR3: 0000000c22d6c000 CR4: 00000000000006e0
  Jul 24 10:12:53 server kernel: [575939.742131] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
  Jul 24 10:12:53 server kernel: [575939.742131] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
  Jul 24 10:12:53 server kernel: [575939.742131] Process nfsd (pid: 2523, threadinfo ffff880422084000, task ffff880425964500)
  Jul 24 10:12:53 server kernel: [575939.742131] Stack:
  Jul 24 10:12:53 server kernel: [575939.742131] ffff880c2268d040 ffff880e29b16cc0 0000000000000000 ffff8807f56418c0
  Jul 24 10:12:53 server kernel: [575939.742131] 0000000000000000 ffff880c2268d180 ffff880422085d50 ffffffffa055d5e3
  Jul 24 10:12:53 server kernel: [575939.742131] ffff880b37cee840 0000000000000000 ffff880c22684000 ffff880c2268d040
  Jul 24 10:12:53 server kernel: [575939.742131] Call Trace:
  Jul 24 10:12:53 server kernel: [575939.742131] [<ffffffffa055d5e3>] nfsd4_set_nfs4_acl+0x143/0x150 [nfsd]
  Jul 24 10:12:53 server kernel: [575939.742131] [<ffffffffa056ab74>] nfsd4_setattr+0xd4/0x130 [nfsd]
  Jul 24 10:12:53 server kernel: [575939.742131] [<ffffffffa0569be8>] nfsd4_proc_compound+0x518/0x6e0 [nfsd]
  Jul 24 10:12:53 server kernel: [575939.742131] [<ffffffffa0558a4b>] nfsd_dispatch+0xeb/0x230 [nfsd]
  Jul 24 10:12:53 server kernel: [575939.742131] [<ffffffffa03ae475>] svc_process_common+0x345/0x690 [sunrpc]
  Jul 24 10:12:53 server kernel: [575939.742131] [<ffffffff81060ad0>] ? try_to_wake_up+0x200/0x200
  Jul 24 10:12:53 server kernel: [575939.742131] [<ffffffffa03aeb12>] svc_process+0x102/0x150 [sunrpc]
  Jul 24 10:12:53 server kernel: [575939.742131] [<ffffffffa05581ad>] nfsd+0xbd/0x160 [nfsd]
  Jul 24 10:12:53 server kernel: [575939.742131] [<ffffffffa05580f0>] ? nfsd_startup+0xf0/0xf0 [nfsd]
  Jul 24 10:12:53 server kernel: [575939.742131] [<ffffffff8108b8cc>] kthread+0x8c/0xa0
  Jul 24 10:12:53 server kernel: [575939.742131] [<ffffffff8166deb4>] kernel_thread_helper+0x4/0x10
  Jul 24 10:12:53 server kernel: [575939.742131] [<ffffffff8108b840>] ? flush_kthread_worker+0xa0/0xa0
  Jul 24 10:12:53 server kernel: [575939.742131] [<ffffffff8166deb0>] ? gs_change+0x13/0x13
  Jul 24 10:12:53 server kernel: [575939.742131] Code: 19 c0 f7 d0 83 e0 02 c3 90 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 66 66 66 66 90 <48> 63 46 10 49 89 fd 49 89 f6 be d0 00 00 00 49 89 d4 4c 8d 3c
  Jul 24 10:12:53 server kernel: [575939.742131] RIP [<ffffffffa055c451>] set_nfsv4_acl_one+0x21/0xb0 [nfsd]
  Jul 24 10:12:53 server kernel: [575939.742131] RSP <ffff880422085ce0>
  Jul 24 10:12:53 server kernel: [575939.742131] CR2: 0000000000000010
  Jul 24 10:12:53 server kernel: [575942.132715] ---[ end trace ba2b82e486b77140 ]---

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