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SubjectRe: [OOPS] 3.0-rc1 cifs

> Yep, mea culpa. This patch should fix it. Martin, can you test it?
> Anyone else have comments?
> Thanks...

Unfortunately, I have to quote Britney: "Oops! I did it again"
Well, not entirely true, the OOPS changed into a BUG, but my samba mount
still doesn't work.

The OOPS to BUG has a interesting diff. Don't know if it really matters,
but some more info about my samba setup. Never such a thing as to much
info. Note, the SAMBA hostname and DNS hostname of the server are
NOT the same.

######## <samba setup> #############
-DNS_hostname :
-SAMBA_hostname : duckman-tm
-ipv4 only :
testparm -v|grep wins :
name resolve order = lmhosts wins host bcast
max wins ttl = 518400
min wins ttl = 21600
wins proxy = No
wins server =,
wins support = No
wins hook =
No Domain Controller or anything. This a student LAN of circa 1000
computers where you can set your SAMBA hostname and workgroup to anything you like. Browse masters
of ad hoc workgroups are decided by elections. Only the WINS servers are
provided as a service of the IT department. I dont have very deep
knowledge of samba, but when I read some specs, my first thought was "this stuff is NOT designed for the way we use it".
However, it works. (Well, with a s*#%load of legitimate samba broadcast

-DNS_hostname =
-SAMBA_hostname = xxxx
-ipv4/ipv6 dual stack
-fstab: // /home/XXXX/docs_sysadmin
cifs guest,uid=XXXX,gid=XXXX,users,auto,nounix,nobrl 0
######### </samba setup> #########

diff -up OOPS BUG

CIFS VFS: default security mechanism requested. The default security
mechanism will be upgraded from ntlm to ntlmv2 in kernel release 2.6.41
-BUG: unable to handle kernel NULL pointer dereference at 00000000000000a0
-IP: [<ffffffffa041e286>] CIFSTCon+0xf6/0x4d0 [cifs]
-PGD 127393067 PUD 129c80067 PMD 0
-Oops: 0000 [#1] SMP
+CIFS VFS: dns_resolve_server_name_to_ip: unable to resolve:
+CIFS VFS: cifs_compose_mount_options: Failed to resolve server part of
\\\sysadmin to IP: -2
+------------[ cut here ]------------
+kernel BUG at mm/slab.c:501!
+invalid opcode: 0000 [#1] SMP


Registering the dns_resolver key type
CIFS VFS: default security mechanism requested. The default security
mechanism will be upgraded from ntlm to ntlmv2 in kernel release 2.6.41
CIFS VFS: dns_resolve_server_name_to_ip: unable to resolve:
CIFS VFS: cifs_compose_mount_options: Failed to resolve server part of
\\\sysadmin to IP: -2
------------[ cut here ]------------
kernel BUG at mm/slab.c:501!
invalid opcode: 0000 [#1] SMP
Modules linked in: des_generic ecb md4 hmac nls_utf8 cifs dns_resolver
nfsd nfs lockd fscache sunrpc xfs fuse radeon ttm drm_kms_helper drm
i2c_algo_bit cfbcopyarea cfbimgblt cfbfillrect loop sg asus_atk0110 usbhid
sr_mod cdrom hid evdev pata_marvell sky2 skge snd_hda_codec_hdmi
snd_hda_codec_analog snd_hda_intel snd_hda_codec snd_hwdep snd_pcm tpm_tis
snd_seq_midi snd_rawmidi tpm snd_seq_midi_event pcspkr tpm_bios snd_seq
uhci_hcd snd_timer snd_seq_device snd i2c_i801 i2c_core ehci_hcd intel_agp
intel_gtt soundcore snd_page_alloc

Pid: 2085, comm: mount.cifs Not tainted 3.0.0-rc1-debug-patched #1 System
manufacturer P5Q-E/P5Q-E
RIP: 0010:[<ffffffff810d19f4>] [<ffffffff810d19f4>] kfree+0x134/0x170
RSP: 0018:ffff880129251cc8 EFLAGS: 00010046
RAX: ffffea000070f420 RBX: ffff8801287e2e00 RCX: ffff88012f3c8800
RDX: 4000000000000000 RSI: 00000000000000d0 RDI: ffffffffa045cebb
RBP: ffff880129251d18 R08: b018000000000000 R09: 000000000000000a
R10: 0000000000000006 R11: dead000000200200 R12: ffffffffa045cebb
R13: 0000000000000282 R14: ffff88012a903400 R15: ffff88012a903800
FS: 00007f6d20b9f700(0000) GS:ffff88012fc00000(0000)
CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
CR2: 00007fb9903dfc58 CR3: 0000000128b43000 CR4: 00000000000406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Process mount.cifs (pid: 2085, threadinfo ffff880129250000, task
ffff880129251c5c ffffffff810ec545 ffff88012f3c8800 ffff88010f876d10
ffff88012f3c8800 ffff8801287e2e00 ffff880129251d80 ffff88010f876d10
ffff88012a903400 ffff88012a903800 ffff880129251d38 ffffffffa043d19f
Call Trace:
[<ffffffff810ec545>] ? __d_instantiate+0x85/0xf0
[<ffffffffa043d19f>] cifs_cleanup_volume_info+0x1f/0x70 [cifs]
[<ffffffffa043123b>] cifs_do_mount+0x11b/0x3b0 [cifs]
[<ffffffff810db35b>] mount_fs+0x1b/0xd0
[<ffffffff810f5c6e>] vfs_kern_mount+0x5e/0xd0
[<ffffffff810f5d4d>] do_kern_mount+0x4d/0x110
[<ffffffff810f732b>] do_mount+0x2cb/0x7d0
[<ffffffff810f78c3>] sys_mount+0x93/0xe0
[<ffffffff8138bdbb>] system_call_fastpath+0x16/0x1b
Code: c8 44 01 09 4c 8b 45 c0 41 fe 46 40 8b 13 4b 8d 34 38 29 c2 4c 89 c7
89 13 89 d2 48 c1 e2 03 e8 53 d2 0c 00 8b 03 e9 47 ff ff ff <0f> 0b eb fe
48 8b 40 10 e9 16 ff ff ff 4c 8d 43 18 89 c2 4c 89
RIP [<ffffffff810d19f4>] kfree+0x134/0x170
RSP <ffff880129251cc8>
---[ end trace cffbbd6be8c5a0f3 ]---

So, we're from OOPS to BUG. I tried gdb, but it won't decode the
kfree+0x134 into something, which I could with the real OOPS.
Some pointers how I can help with gdb? mentions
only OOPS, no BUG.

Greetz Martijn
(BTW, I will mostly be of the net a couple of days, so my reply's can take
a while)

> -----------------------[snip]--------------------
> [PATCH] cifs: correctly handle NULL tcon pointer in CIFSTCon
> Long ago (in commit 00e485b0), I added some code to handle share-level
> passwords in CIFSTCon. That code ignored the fact that it's legit to
> pass in a NULL tcon pointer when connecting to the IPC$ share on the
> server.
> This wasn't really a problem until recently as we only called CIFSTCon
> this way when the server returned -EREMOTE. With the introduction of
> commit c1508ca2 however, it gets called this way on every mount, causing
> an oops when share-level security is in effect.
> Fix this by simply treating a NULL tcon pointer as if user-level
> security were in effect. I'm not aware of any servers that protect the
> IPC$ share with a specific password anyway. Also, add a comment to the
> top of CIFSTCon to ensure that we don't make the same mistake again.
> Reported-by: Martijn Uffing <>
> Signed-off-by: Jeff Layton <>
> ---
> fs/cifs/connect.c | 6 +++++-
> 1 files changed, 5 insertions(+), 1 deletions(-)
> diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
> index 7b6cad2..fa5a5d7 100644
> --- a/fs/cifs/connect.c
> +++ b/fs/cifs/connect.c
> @@ -3174,6 +3174,10 @@ out:
> return rc;
> }
> +/*
> + * Issue a TREE_CONNECT request. Note that for IPC$ shares, that the tcon
> + * pointer may be NULL.
> + */
> int
> CIFSTCon(unsigned int xid, struct cifs_ses *ses,
> const char *tree, struct cifs_tcon *tcon,
> @@ -3208,7 +3212,7 @@ CIFSTCon(unsigned int xid, struct cifs_ses *ses,
> pSMB->AndXCommand = 0xFF;
> pSMB->Flags = cpu_to_le16(TCON_EXTENDED_SECINFO);
> bcc_ptr = &pSMB->Password[0];
> - if ((ses->server->sec_mode) & SECMODE_USER) {
> + if (!tcon || (ses->server->sec_mode & SECMODE_USER)) {
> pSMB->PasswordLength = cpu_to_le16(1); /* minimum */
> *bcc_ptr = 0; /* password is null byte */
> bcc_ptr++; /* skip password */
> --

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