Currently, we allow the pending_mid_q to grow without bound with
SIGKILL'ed processes. This could eventually be a DoS'able problem. An
unprivileged user could a process that does a long-running call and then
SIGKILL it.
If he can also intercept the NT_CANCEL calls or the replies from the
server, then the pending_mid_q could grow very large, possibly even to
2^16 entries which might leave GetNextMid in an infinite loop. Fix this
by imposing a hard limit of 32k calls per server. If we cross that
limit, set the tcpStatus to CifsNeedReconnect to force cifsd to
eventually reconnect the socket and clean out the pending_mid_q.
While we're at it, clean up the function a bit and eliminate an
unnecessary NULL pointer check.
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Reviewed-by: Shirish Pargaonkar <shirishpargaonkar@gmail.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
If we kill the process while it's sending on a socket then the
kernel_sendmsg will return -EINTR. This is normal. No need to spam the
ring buffer with this info.
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
...just cleanup. There should be no behavior change.
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Reviewed-by: Pavel Shilovsky <piastryyy@gmail.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
Use the new send_nt_cancel function to send an NT_CANCEL when the
process is delivered a fatal signal. This is a "best effort" enterprise
however, so don't bother to check the return code. There's nothing we
can reasonably do if it fails anyway.
Reviewed-by: Pavel Shilovsky <piastryyy@gmail.com>
Reviewed-by: Suresh Jayaraman <sjayaraman@suse.de>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
Currently, when a request is cancelled via signal, we delete the mid
immediately. If the request was already transmitted however, the client
is still likely to receive a response. When it does, it won't recognize
it however and will pop a printk.
It's also a little dangerous to just delete the mid entry like this. We
may end up reusing that mid. If we do then we could potentially get the
response from the first request confused with the later one.
Prevent the reuse of mids by marking them as cancelled and keeping them
on the pending_mid_q list. If the reply comes in, we'll delete it from
the list then. If it never comes, then we'll delete it at reconnect
or when cifsd comes down.
Reviewed-by: Pavel Shilovsky <piastryyy@gmail.com>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
fs/cifs/link.c: In function ‘symlink_hash’:
fs/cifs/link.c:58:3: warning: ‘rc’ may be used uninitialized in this
function [-Wuninitialized]
fs/cifs/smbencrypt.c: In function ‘mdfour’:
fs/cifs/smbencrypt.c:61:3: warning: ‘rc’ may be used uninitialized in this
function [-Wuninitialized]
Reviewed-by: Shirish Pargaonkar <shirishpargaonkar@gmail.com>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
Replaced md4 hashing function local to cifs module with kernel crypto APIs.
As a result, md4 hashing function and its supporting functions in
file md4.c are not needed anymore.
Cleaned up function declarations, removed forward function declarations,
and removed a header file that is being deleted from being included.
Verified that sec=ntlm/i, sec=ntlmv2/i, and sec=ntlmssp/i work correctly.
Signed-off-by: Shirish Pargaonkar <shirishpargaonkar@gmail.com>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
Use for switching on strict cache mode. In this mode the
client reads from the cache all the time it has Oplock Level II,
otherwise - read from the server. As for write - the client stores
a data in the cache in Exclusive Oplock case, otherwise - write
directly to the server.
Signed-off-by: Pavel Shilovsky <piastryyy@gmail.com>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
If we don't have Exclusive oplock we write a data to the server.
Also set invalidate_mapping flag on the inode if we wrote something
to the server. Add cifs_iovec_write to let the client write iovec
buffers through CIFSSMBWrite2.
Signed-off-by: Pavel Shilovsky <piastryyy@gmail.com>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
Replace remaining use of md5 hash functions local to cifs module
with kernel crypto APIs.
Remove header and source file containing those local functions.
Signed-off-by: Shirish Pargaonkar <shirishpargaonkar@gmail.com>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
Teach cifs about network namespaces, so mounting uses adresses/routing
visible from the container rather than from init context.
A container is a chroot on steroids that changes more than just the root
filesystem the new processes see. One thing containers can isolate is
"network namespaces", meaning each container can have its own set of
ethernet interfaces, each with its own own IP address and routing to the
outside world. And if you open a socket in _userspace_ from processes
within such a container, this works fine.
But sockets opened from within the kernel still use a single global
networking context in a lot of places, meaning the new socket's address
and routing are correct for PID 1 on the host, but are _not_ what
userspace processes in the container get to use.
So when you mount a network filesystem from within in a container, the
mount code in the CIFS driver uses the host's networking context and not
the container's networking context, so it gets the wrong address, uses
the wrong routing, and may even try to go out an interface that the
container can't even access... Bad stuff.
This patch copies the mount process's network context into the CIFS
structure that stores the rest of the server information for that mount
point, and changes the socket open code to use the saved network context
instead of the global network context. I.E. "when you attempt to use
these addresses, do so relative to THIS set of network interfaces and
routing rules, not the old global context from back before we supported
containers".
The big long HOWTO sets up a test environment on the assumption you've
never used ocntainers before. It basically says:
1) configure and build a new kernel that has container support
2) build a new root filesystem that includes the userspace container
control package (LXC)
3) package/run them under KVM (so you don't have to mess up your host
system in order to play with containers).
4) set up some containers under the KVM system
5) set up contradictory routing in the KVM system and the container so
that the host and the container see different things for the same address
6) try to mount a CIFS share from both contexts so you can both force it
to work and force it to fail.
For a long drawn out test reproduction sequence, see:
http://landley.livejournal.com/47024.htmlhttp://landley.livejournal.com/47205.htmlhttp://landley.livejournal.com/47476.html
Signed-off-by: Rob Landley <rlandley@parallels.com>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
In fs/cifs/cifs_dfs_ref.c::cifs_dfs_do_automount() we have this code:
...
mnt = ERR_PTR(-EINVAL);
if (IS_ERR(tlink)) {
mnt = ERR_CAST(tlink);
goto free_full_path;
}
ses = tlink_tcon(tlink)->ses;
rc = get_dfs_path(xid, ses, full_path + 1, cifs_sb->local_nls,
&num_referrals, &referrals,
cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MAP_SPECIAL_CHR);
cifs_put_tlink(tlink);
mnt = ERR_PTR(-ENOENT);
...
The assignment of 'mnt = ERR_PTR(-EINVAL);' is completely pointless. If we
take the 'if (IS_ERR(tlink))' branch we'll set 'mnt' again and we'll also
do so if we do not take the branch. There is no way we'll ever use 'mnt'
with the assigned 'ERR_PTR(-EINVAL)' value, so we may as well just remove
the pointless assignment.
Signed-off-by: Jesper Juhl <jj@chaosbits.net>
Signed-off-by: Steve French <sfrench@us.ibm.com>
Make sure that CIFSSMBEcho can handle unaligned fields. Also fix a minor
bug that causes this warning:
fs/cifs/cifssmb.c: In function 'CIFSSMBEcho':
fs/cifs/cifssmb.c:740: warning: large integer implicitly truncated to unsigned type
...WordCount is u8, not __le16, so no need to convert it.
This patch should apply cleanly on top of the rest of the patchset to
clean up unaligned access.
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
Move cifsConvertToUCS to cifs_unicode.c where all of the other unicode
related functions live. Have it store mapped characters in 'temp' and
then use put_unaligned_le16 to copy it to the target buffer. Also fix
the comments to match kernel coding style.
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Acked-by: Pavel Shilovsky <piastryyy@gmail.com>
Reviewed-by: Shirish Pargaonkar <shirishpargaonkar@gmail.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
Make sure we use get/put_unaligned routines when accessing wide
character strings.
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Acked-by: Pavel Shilovsky <piastryyy@gmail.com>
Reviewed-by: Shirish Pargaonkar <shirishpargaonkar@gmail.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Acked-by: Pavel Shilovsky <piastryyy@gmail.com>
Reviewed-by: Shirish Pargaonkar <shirishpargaonkar@gmail.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
...and clean up function to reduce indentation.
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Acked-by: Pavel Shilovsky <piastryyy@gmail.com>
Reviewed-by: Shirish Pargaonkar <shirishpargaonkar@gmail.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
It's possible that when we access the ByteCount that the alignment
will be off. Most CPUs deal with that transparently, but there's
usually some performance impact. Some CPUs raise an exception on
unaligned accesses.
Fix this by accessing the byte count using the get_unaligned and
put_unaligned inlined functions. While we're at it, fix the types
of some of the variables that end up getting returns from these
functions.
Acked-by: Pavel Shilovsky <piastryyy@gmail.com>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
Remove fields that are completely unused, and rearrange struct
according to recommendations by "pahole".
Before:
/* size: 1112, cachelines: 18, members: 49 */
/* sum members: 1086, holes: 8, sum holes: 26 */
/* bit holes: 1, sum bit holes: 7 bits */
/* last cacheline: 24 bytes */
After:
/* size: 1072, cachelines: 17, members: 42 */
/* sum members: 1065, holes: 3, sum holes: 7 */
/* last cacheline: 48 bytes */
...savings of 40 bytes per struct on x86_64. 21 bytes by field removal,
and 19 by reorganizing to eliminate holes.
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
Read from the cache if we have at least Level II oplock - otherwise
read from the server. Add cifs_user_readv to let the client read into
iovec buffers.
Reviewed-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Pavel Shilovsky <piastryyy@gmail.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
Invalidate inode mapping if we don't have at least Level II oplock.
Reviewed-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Pavel Shilovsky <piastryyy@gmail.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
Invalidate inode mapping if we don't have at least Level II oplock in
cifs_strict_fsync. Also remove filemap_write_and_wait call from cifs_fsync
because it is previously called from vfs_fsync_range. Add file operations'
structures for strict cache mode.
Reviewed-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Pavel Shilovsky <piastryyy@gmail.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
On strict cache mode when we close the last file handle of the inode we
should set invalid_mapping flag on this inode to prevent data coherency
problem when we open it again but it has been modified on the server.
Reviewed-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Pavel Shilovsky <piastryyy@gmail.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
The NT_CANCEL command looks just like the original command, except for a
few small differences. The send_nt_cancel function however currently takes
a tcon, which we don't have in SendReceive and SendReceive2.
Instead of "respinning" the entire header for an NT_CANCEL, just mangle
the existing header by replacing just the fields we need. This means we
don't need a tcon and allows us to call it from other places.
Reviewed-by: Pavel Shilovsky <piastryyy@gmail.com>
Reviewed-by: Suresh Jayaraman <sjayaraman@suse.de>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
Since we don't time out individual requests anymore, remove the code
that we used to use for setting timeouts on different requests.
Reviewed-by: Pavel Shilovsky <piastryyy@gmail.com>
Reviewed-by: Suresh Jayaraman <sjayaraman@suse.de>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
If the server isn't responding to echoes, we don't want to leave tasks
hung waiting for it to reply. At that point, we'll want to reconnect
so that soft mounts can return an error to userspace quickly.
If the client hasn't received a reply after a specified number of echo
intervals, assume that the transport is down and attempt to reconnect
the socket.
The number of echo_intervals to wait before attempting to reconnect is
tunable via a module parameter. Setting it to 0, means that the client
will never attempt to reconnect. The default is 5.
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Add a function that will send a request, and set up the mid for an
async reply.
Reviewed-by: Suresh Jayaraman <sjayaraman@suse.de>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
In order to incorporate async requests, we need to allow for a more
general way to do things on receive, rather than just waking up a
process.
Turn the task pointer in the mid_q_entry into a callback function and a
generic data pointer. When a response comes in, or the socket is
reconnected, cifsd can call the callback function in order to wake up
the process.
The default is to just wake up the current process which should mean no
change in behavior for existing code.
Also, clean up the locking in cifs_reconnect. There doesn't seem to be
any need to hold both the srv_mutex and GlobalMid_Lock when walking the
list of mids.
Reviewed-by: Suresh Jayaraman <sjayaraman@suse.de>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
Make it use a switch statement based on the value of the midStatus. If
the resp_buf is set, then MID_RESPONSE_RECEIVED is too.
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
We only want to force a reconnect to the server under very limited and
specific circumstances. Now that we have processes waiting indefinitely
for responses, we shouldn't reach this point unless a reconnect is
already in process. Thus, there's no reason to re-mark the server for
reconnect here.
Reviewed-by: Suresh Jayaraman <sjayaraman@suse.de>
Reviewed-by: Pavel Shilovsky <piastryyy@gmail.com>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
The client should not be timing out on individual SMB requests. Too much
of the state between client and server is tied to the state of the
socket. If we time out requests and issue spurious disconnects then that
comprimises data integrity.
Instead of doing this complicated dance where we try to decide how long
to wait for a response for particular requests, have the client instead
wait indefinitely for a response. Also, use a TASK_KILLABLE sleep here
so that fatal signals will break out of this waiting.
Later patches will add support for detecting dead peers and forcing
reconnects based on that.
Reviewed-by: Suresh Jayaraman <sjayaraman@suse.de>
Reviewed-by: Pavel Shilovsky <piastryyy@gmail.com>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
If a DACL has entries for ACEs for SID Everyone and Authenticated Users,
factor in mask in respective entries during calculation of permissions
for all three, user, group, and other.
http://technet.microsoft.com/en-us/library/bb463216.aspx
Signed-off-by: Shirish Pargaonkar <shirishpargaonkar@gmail.com>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
NTLM response length was changed to 16 bytes instead of 24 bytes
that are sent in Tree Connection Request during share-level security
share mounts. Revert it back to 24 bytes.
Reported-and-Tested-by: Grzegorz Ozanski <grzegorz.ozanski@intel.com>
Acked-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Shirish Pargaonkar <shirishpargaonkar@gmail.com>
Acked-by: Suresh Jayaraman <sjayaraman@suse.de>
Cc: stable@kernel.org
Signed-off-by: Steve French <sfrench@us.ibm.com>
Reviewed-by: Suresh Jayaraman <sjayaraman@suse.de>
Reviewed-by: Pavel Shilovsky <piastryyy@gmail.com>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
In later patches, we're going to need to have finer-grained control
over the addition and removal of these structs from the pending_mid_q
and we'll need to be able to call the destructor while holding the
spinlock. Move the locked sections out of both routines and into
the callers. Fix up current callers of DeleteMidQEntry to call a new
routine that dequeues the entry and then destroys it.
Reviewed-by: Suresh Jayaraman <sjayaraman@suse.de>
Reviewed-by: Pavel Shilovsky <piastryyy@gmail.com>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
It's an atomic_t and the code accesses the "counter" field in it directly
instead of using atomic_read(). It also is sometimes accessed under a
spinlock and sometimes not. Move it out of the spinlock since we don't need
belt-and-suspenders for something that's just informational.
Reviewed-by: Suresh Jayaraman <sjayaraman@suse.de>
Reviewed-by: Pavel Shilovsky <piastryyy@gmail.com>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
The cifsSesInfo pointer is only used to get at the server.
Reviewed-by: Suresh Jayaraman <sjayaraman@suse.de>
Reviewed-by: Pavel Shilovsky <piastryyy@gmail.com>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
The TCP_Server_Info is refcounted and every SMB session holds a
reference to it. Thus, smb_ses_list is always going to be empty when
cifsd is coming down. This is dead code.
Reviewed-by: Suresh Jayaraman <sjayaraman@suse.de>
Reviewed-by: Pavel Shilovsky <piastryyy@gmail.com>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
If CIFSSMBWrite2 returns -EAGAIN, then the error should be considered
temporary. CIFS should retry the write instead of setting an error on
the mapping and returning.
For WB_SYNC_ALL, just retry the write immediately. In the WB_SYNC_NONE
case, call redirty_page_for_writeback on all of the pages that didn't
get written out and then move on.
Also, fix up the handling of a short write with a successful return
code. MS-CIFS says that 0 bytes_written means ENOSPC or EFBIG. It
doesn't mention what a short, but non-zero write means, so for now
treat it as we would an -EAGAIN return.
Reviewed-by: Suresh Jayaraman <sjayaraman@suse.de>
Reviewed-by: Pavel Shilovsky <piastryyy@gmail.com>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
When we get oplock break notification we should set the appropriate
value of OplockLevel field in oplock break acknowledge according to
the oplock level held by the client in this time. As we only can have
level II oplock or no oplock in the case of oplock break, we should be
aware only about clientCanCacheRead field in cifsInodeInfo structure.
Also fix bug connected with wrong interpretation of OplockLevel field
during oplock break notification processing.
Signed-off-by: Pavel Shilovsky <piastryyy@gmail.com>
Cc: <stable@kernel.org>
Signed-off-by: Steve French <sfrench@us.ibm.com>
* git://git.kernel.org/pub/scm/linux/kernel/git/sfrench/cifs-2.6:
cifs: add cruid= mount option
cifs: cFYI the entire error code in map_smb_to_linux_error
Unexport do_add_mount() and make ->d_automount() return the vfsmount to be
added rather than calling do_add_mount() itself. follow_automount() will then
do the addition.
This slightly complicates things as ->d_automount() normally wants to add the
new vfsmount to an expiration list and start an expiration timer. The problem
with that is that the vfsmount will be deleted if it has a refcount of 1 and
the timer will not repeat if the expiration list is empty.
To this end, we require the vfsmount to be returned from d_automount() with a
refcount of (at least) 2. One of these refs will be dropped unconditionally.
In addition, follow_automount() must get a 3rd ref around the call to
do_add_mount() lest it eat a ref and return an error, leaving the mount we
have open to being expired as we would otherwise have only 1 ref on it.
d_automount() should also add the the vfsmount to the expiration list (by
calling mnt_set_expiry()) and start the expiration timer before returning, if
this mechanism is to be used. The vfsmount will be unlinked from the
expiration list by follow_automount() if do_add_mount() fails.
This patch also fixes the call to do_add_mount() for AFS to propagate the mount
flags from the parent vfsmount.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Make CIFS use the new d_automount() dentry operation rather than abusing
follow_link() on directories.
[NOTE: THIS IS UNTESTED!]
Signed-off-by: David Howells <dhowells@redhat.com>
Cc: Steve French <sfrench@samba.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Add a dentry op (d_manage) to permit a filesystem to hold a process and make it
sleep when it tries to transit away from one of that filesystem's directories
during a pathwalk. The operation is keyed off a new dentry flag
(DCACHE_MANAGE_TRANSIT).
The filesystem is allowed to be selective about which processes it holds and
which it permits to continue on or prohibits from transiting from each flagged
directory. This will allow autofs to hold up client processes whilst letting
its userspace daemon through to maintain the directory or the stuff behind it
or mounted upon it.
The ->d_manage() dentry operation:
int (*d_manage)(struct path *path, bool mounting_here);
takes a pointer to the directory about to be transited away from and a flag
indicating whether the transit is undertaken by do_add_mount() or
do_move_mount() skipping through a pile of filesystems mounted on a mountpoint.
It should return 0 if successful and to let the process continue on its way;
-EISDIR to prohibit the caller from skipping to overmounted filesystems or
automounting, and to use this directory; or some other error code to return to
the user.
->d_manage() is called with namespace_sem writelocked if mounting_here is true
and no other locks held, so it may sleep. However, if mounting_here is true,
it may not initiate or wait for a mount or unmount upon the parameter
directory, even if the act is actually performed by userspace.
Within fs/namei.c, follow_managed() is extended to check with d_manage() first
on each managed directory, before transiting away from it or attempting to
automount upon it.
follow_down() is renamed follow_down_one() and should only be used where the
filesystem deliberately intends to avoid management steps (e.g. autofs).
A new follow_down() is added that incorporates the loop done by all other
callers of follow_down() (do_add/move_mount(), autofs and NFSD; whilst AFS, NFS
and CIFS do use it, their use is removed by converting them to use
d_automount()). The new follow_down() calls d_manage() as appropriate. It
also takes an extra parameter to indicate if it is being called from mount code
(with namespace_sem writelocked) which it passes to d_manage(). follow_down()
ignores automount points so that it can be used to mount on them.
__follow_mount_rcu() is made to abort rcu-walk mode if it hits a directory with
DCACHE_MANAGE_TRANSIT set on the basis that we're probably going to have to
sleep. It would be possible to enter d_manage() in rcu-walk mode too, and have
that determine whether to abort or not itself. That would allow the autofs
daemon to continue on in rcu-walk mode.
Note that DCACHE_MANAGE_TRANSIT on a directory should be cleared when it isn't
required as every tranist from that directory will cause d_manage() to be
invoked. It can always be set again when necessary.
==========================
WHAT THIS MEANS FOR AUTOFS
==========================
Autofs currently uses the lookup() inode op and the d_revalidate() dentry op to
trigger the automounting of indirect mounts, and both of these can be called
with i_mutex held.
autofs knows that the i_mutex will be held by the caller in lookup(), and so
can drop it before invoking the daemon - but this isn't so for d_revalidate(),
since the lock is only held on _some_ of the code paths that call it. This
means that autofs can't risk dropping i_mutex from its d_revalidate() function
before it calls the daemon.
The bug could manifest itself as, for example, a process that's trying to
validate an automount dentry that gets made to wait because that dentry is
expired and needs cleaning up:
mkdir S ffffffff8014e05a 0 32580 24956
Call Trace:
[<ffffffff885371fd>] :autofs4:autofs4_wait+0x674/0x897
[<ffffffff80127f7d>] avc_has_perm+0x46/0x58
[<ffffffff8009fdcf>] autoremove_wake_function+0x0/0x2e
[<ffffffff88537be6>] :autofs4:autofs4_expire_wait+0x41/0x6b
[<ffffffff88535cfc>] :autofs4:autofs4_revalidate+0x91/0x149
[<ffffffff80036d96>] __lookup_hash+0xa0/0x12f
[<ffffffff80057a2f>] lookup_create+0x46/0x80
[<ffffffff800e6e31>] sys_mkdirat+0x56/0xe4
versus the automount daemon which wants to remove that dentry, but can't
because the normal process is holding the i_mutex lock:
automount D ffffffff8014e05a 0 32581 1 32561
Call Trace:
[<ffffffff80063c3f>] __mutex_lock_slowpath+0x60/0x9b
[<ffffffff8000ccf1>] do_path_lookup+0x2ca/0x2f1
[<ffffffff80063c89>] .text.lock.mutex+0xf/0x14
[<ffffffff800e6d55>] do_rmdir+0x77/0xde
[<ffffffff8005d229>] tracesys+0x71/0xe0
[<ffffffff8005d28d>] tracesys+0xd5/0xe0
which means that the system is deadlocked.
This patch allows autofs to hold up normal processes whilst the daemon goes
ahead and does things to the dentry tree behind the automouter point without
risking a deadlock as almost no locks are held in d_manage() and none in
d_automount().
Signed-off-by: David Howells <dhowells@redhat.com>
Was-Acked-by: Ian Kent <raven@themaw.net>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
In commit 3e4b3e1f we separated the "uid" mount option such that it
no longer determined the owner of the credential cache by default. When
we did this, we added a new option to cifs.upcall (--legacy-uid) to
try to make it so that it would behave the same was as it did before.
This ignored a rather important point -- the kernel has no way to know
what options are being passed to cifs.upcall, so it doesn't know what
uid it should use to determine whether to match an existing krb5 session.
The simplest solution is to simply add a new "cruid=" mount option that
only governs the uid owner of the credential cache for the mount.
Unfortunately, this means that the --legacy-uid option in cifs.upcall was
ill-considered and is now useless, but I don't see a better way to deal
with this.
A patch for the mount.cifs manpage will follow once this patch has been
accepted.
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
