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

[Jeff Layton]

 On Sat, 16 May 2009 22:13:31 -0400
Jeff Layton <jlayton@xxxxxxxxxx> wrote:

> On Sat, 16 May 2009 22:55:58 +0200
> Luca Tettamanti <kronos.it@xxxxxxxxx> 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.
> 

Oops, wrong patch...this is the right one.

-- 
Jeff Layton <jlayton@xxxxxxxxxx>