[linux-cifs-client] Re: [2.6.30-rc6] cifs_close: NULL pointer dereference

[Shirish Pargaonkar]

On Sat, May 16, 2009 at 9:13 PM, Jeff Layton <jlayton at redhat.com> wrote:
> On Sat, 16 May 2009 22:55:58 +0200
> Luca Tettamanti <kronos.it at gmail.com> wrote:
>
>> On Sat, May 16, 2009 at 06:28:13PM +0200, Luca Tettamanti wrote:
>> > Hello,
>> > I just hit a NULL pointer dereference in cifs_close while accessing a file on a
>> > remote Samba shared directory.
>> [...]
>> > BUG: unable to handle kernel NULL pointer dereference at 0000000000000008
>> > IP: [<ffffffffa05f105c>] cifs_close+0x1c1/0x2e8 [cifs]
>>
>> Ok, I've reproduced this on a machine with a serial port :)
>>
>> 0xffffffff803574e0 in list_del (entry=0xffff8800ac184210)
>> at /home/kronos/src/linux-2.6.git/lib/list_debug.c:46
>> 46              WARN(entry->prev->next != entry,
>> (gdb) bt
>> #0  0xffffffff803574e0 in list_del (entry=0xffff8800ac184210)
>>     at /home/kronos/src/linux-2.6.git/lib/list_debug.c:46
>> #1  0xffffffff80319588 in cifs_close (inode=0xffff8800b8d5f088, file=0xffff8800ad8f6d00)
>>     at /home/kronos/src/linux-2.6.git/fs/cifs/file.c:670
>> #2  0xffffffff8029d95e in __fput (file=0xffff8800ad8f6d00)
>>     at /home/kronos/src/linux-2.6.git/fs/file_table.c:281
>> #3  0xffffffff8029da32 in fput (file=0xffff8800ac184210)
>>     at /home/kronos/src/linux-2.6.git/fs/file_table.c:227
>> #4  0xffffffff8029ad30 in filp_close (filp=0xffff8800ad8f6d00, id=0xffff880037a3e080)
>>     at /home/kronos/src/linux-2.6.git/fs/open.c:1108
>> #5  0xffffffff8029ade0 in sys_close (fd=0)
>>     at /home/kronos/src/linux-2.6.git/fs/open.c:1137
>> #6  0xffffffff802271e4 in sysenter_dispatch ()
>>     at /home/kronos/src/linux-2.6.git/arch/x86/ia32/ia32entry.S:161
>> #7  0x0000000000000000 in ?? ()
>>
>> (gdb) f 1
>> #1  0xffffffff80319588 in cifs_close (inode=0xffff8800b8d5f088, file=0xffff8800ad8f6d00)
>>     at /home/kronos/src/linux-2.6.git/fs/cifs/file.c:670
>> 670                     list_del(&pSMBFile->flist);
>>
>> (gdb) p *&pSMBFile->flist
>> $2 = {next = 0x0, prev = 0x0}
>>
>> (gdb) p *&pSMBFile->tlist
>> $5 = {next = 0x0, prev = 0x0}
>>
>> So both flist and tlist were not initilized in cifs_open.
>>
>> The content of the whole pSMBFile structure:
>>
>> (gdb) p *pSMBFile
>> $6 = {tlist = {next = 0x0, prev = 0x0}, flist = {next = 0x0, prev = 0x0}, uid = 0, pid = 5322, netfid = 13880,
>>   pfile = 0xffff8800ad8f6d00, pInode = 0xffff8800b8d5f088, lock_mutex = {count = {counter = 1}, wait_lock = {raw_lock = {
>>         slock = 514}, magic = 3735899821, owner_cpu = 4294967295, owner = 0xffffffffffffffff, dep_map = {
>>         key = 0xffffffff806a5c98, class_cache = 0x0, name = 0xffffffff80537308 "&lock->wait_lock"}}, wait_list = {
>>       next = 0xffff8800ac184278, prev = 0xffff8800ac184278}, owner = 0x0, name = 0x0, magic = 0xffff8800ac184240, dep_map = {
>>       key = 0xffffffff80d7ff50, class_cache = 0xffffffff80835400, name = 0xffffffff8054cdfa "&private_data->lock_mutex"}},
>>   llist = {next = 0xffff8800ac1842b8, prev = 0xffff8800ac1842b8}, closePend = true, invalidHandle = false,
>>   messageMode = false, wrtPending = {counter = 0}, fh_mutex = {count = {counter = 1}, wait_lock = {raw_lock = {slock = 0},
>>       magic = 3735899821, owner_cpu = 4294967295, owner = 0xffffffffffffffff, dep_map = {key = 0xffffffff806a5c98,
>>         class_cache = 0x0, name = 0xffffffff80537308 "&lock->wait_lock"}}, wait_list = {next = 0xffff8800ac184308,
>>       prev = 0xffff8800ac184308}, owner = 0x0, name = 0x0, magic = 0xffff8800ac1842d0, dep_map = {key = 0xffffffff80d7ff58,
>>       class_cache = 0x0, name = 0xffffffff8054cde2 "&private_data->fh_mutex"}}, srch_inf = {index_of_last_entry = 0,
>>     entries_in_buffer = 0, info_level = 0, resume_key = 0, ntwrk_buf_start = 0x0, srch_entries_start = 0x0, last_entry = 0x0,
>>     presume_name = 0x0, resume_name_len = 0, endOfSearch = false, emptyDir = false, unicode = false, smallBuf = false}}
>>
>
> Luca...thanks for the bug report and analysis. I've been able to
> reproduce this too against 3.3.2. The attached patch reverts the open
> with lookup intent functionality that was added at the beginning of the
> 2.6.30 cycle. This fixes the problem for me.
>
> Steve and Shirish...given that we've already seen a couple of
> regressions from these patches, I'd like to see them reverted until
> they have been better tested.
>
> --
> Jeff Layton <jlayton at redhat.com>
>

Does this happen inspite of the patch 90e4ee5d311d4e0729daa676b1d7f754265b5874