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

[Jeff Layton]

On Sun, 17 May 2009 09:40:44 -0500
Shirish Pargaonkar <shirishpargaonkar@xxxxxxxxx> wrote:

> On Sat, May 16, 2009 at 9:13 PM, 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.
> >
> > --
> > Jeff Layton <jlayton@xxxxxxxxxx>
> >
> 
> Does this happen inspite of the patch 90e4ee5d311d4e0729daa676b1d7f754265b5874

Yes. It's trivial to reproduce against a samba 3.3.2 server.

-- 
Jeff Layton <jlayton@xxxxxxxxxx>
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