From patchwork Tue Aug 25 21:23:35 2009 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Dave Kleikamp X-Patchwork-Id: 43813 Received: from lists.samba.org (fn.samba.org [216.83.154.106]) by demeter.kernel.org (8.14.2/8.14.2) with ESMTP id n7PLNina022341 for ; Tue, 25 Aug 2009 21:23:45 GMT Received: from fn.samba.org (localhost [127.0.0.1]) by lists.samba.org (Postfix) with ESMTP id 4E69CAD0CC; Tue, 25 Aug 2009 15:15:41 -0600 (MDT) X-Spam-Checker-Version: SpamAssassin 3.2.5 (2008-06-10) on fn.samba.org X-Spam-Level: X-Spam-Status: No, score=-1.4 required=3.8 tests=AWL, BAYES_00 autolearn=ham version=3.2.5 X-Original-To: linux-cifs-client@lists.samba.org Delivered-To: linux-cifs-client@lists.samba.org Received: from e7.ny.us.ibm.com (e7.ny.us.ibm.com [32.97.182.137]) by lists.samba.org (Postfix) with ESMTP id 834A6AC373 for ; Tue, 25 Aug 2009 15:15:35 -0600 (MDT) Received: from d01relay02.pok.ibm.com (d01relay02.pok.ibm.com [9.56.227.234]) by e7.ny.us.ibm.com (8.14.3/8.13.1) with ESMTP id n7PLMOxR017179 for ; Tue, 25 Aug 2009 17:22:24 -0400 Received: from d01av03.pok.ibm.com (d01av03.pok.ibm.com [9.56.224.217]) by d01relay02.pok.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id n7PLNbZ3253468 for ; Tue, 25 Aug 2009 17:23:37 -0400 Received: from d01av03.pok.ibm.com (loopback [127.0.0.1]) by d01av03.pok.ibm.com (8.12.11.20060308/8.13.3) with ESMTP id n7PLNbF7021618 for ; Tue, 25 Aug 2009 17:23:37 -0400 Received: from [9.41.46.179] (norville.austin.ibm.com [9.41.46.179]) by d01av03.pok.ibm.com (8.12.11.20060308/8.12.11) with ESMTP id n7PLNawp021574; Tue, 25 Aug 2009 17:23:36 -0400 From: Dave Kleikamp To: Jeff Layton In-Reply-To: <20090818124344.6e59221c@tlielax.poochiereds.net> References: <4a4634330908160938k4ea9a68ey496c7aed861c543b@mail.gmail.com> <20090817155052.27c7a9b0@tlielax.poochiereds.net> <4a4634330908171331n28e7d9fcif14b606f935271f8@mail.gmail.com> <20090818071550.53c57a67@tlielax.poochiereds.net> <4a4634330908180823q74b67001if55a7521da8a38bd@mail.gmail.com> <20090818124344.6e59221c@tlielax.poochiereds.net> Date: Tue, 25 Aug 2009 16:23:35 -0500 Message-Id: <1251235415.27359.116.camel@norville.austin.ibm.com> Mime-Version: 1.0 X-Mailer: Evolution 2.24.5 Cc: linux-cifs-client@lists.samba.org Subject: Re: [linux-cifs-client] [patch] prevent slab corruption by fixing race codition in cifs X-BeenThere: linux-cifs-client@lists.samba.org X-Mailman-Version: 2.1.12 Precedence: list List-Id: The Linux CIFS VFS client List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: linux-cifs-client-bounces@lists.samba.org Errors-To: linux-cifs-client-bounces@lists.samba.org On Tue, 2009-08-18 at 12:43 -0400, Jeff Layton wrote: > On Tue, 18 Aug 2009 10:23:09 -0500 > Shirish Pargaonkar wrote: > > > On Tue, Aug 18, 2009 at 6:15 AM, Jeff Layton wrote: > > > I'm less than thrilled with this patch. This looks like like it's > > > layering more complexity onto a codepath that is already far too > > > complex for what it does. > > > > > > Is it not possible to just use regular old refcounting for the open > > > filehandles? i.e. have each user of the filehandle take a reference, > > > and the last one to put it does the actual close. That seems like a > > > much better approach to me than all of this crazy flag business. > > > > > > > I think this needs, some re-designing the code right? > > > > My vote would be "yes". Redesign and simplify the code rather than > adding in new hacks to work around the flaws in the existing design. > > Redesigning it with actual refcounting (and not this half-assed > wrtPending stuff) seems like a much better approach. How's this? Untested so far: cifs: Replace wrtPending with a real reference count Currently, cifs_close() tries to wait until all I/O is complete and then frees the file private data. If I/O does not completely in a reasonable amount of time it frees the structure anyway, leaving a potential use- after-free situation. This patch changes the wrtPending counter to a complete reference count and lets the last user free the structure. WARNING: compile tested only at this time Signed-off-by: Dave Kleikamp diff --git a/fs/cifs/cifsacl.c b/fs/cifs/cifsacl.c index 6941c22..7dfe084 100644 --- a/fs/cifs/cifsacl.c +++ b/fs/cifs/cifsacl.c @@ -607,7 +607,7 @@ static struct cifs_ntsd *get_cifs_acl(struct cifs_sb_info *cifs_sb, return get_cifs_acl_by_path(cifs_sb, path, pacllen); pntsd = get_cifs_acl_by_fid(cifs_sb, open_file->netfid, pacllen); - atomic_dec(&open_file->wrtPending); + cifsFileInfo_put(open_file); return pntsd; } @@ -665,7 +665,7 @@ static int set_cifs_acl(struct cifs_ntsd *pnntsd, __u32 acllen, return set_cifs_acl_by_path(cifs_sb, path, pnntsd, acllen); rc = set_cifs_acl_by_fid(cifs_sb, open_file->netfid, pnntsd, acllen); - atomic_dec(&open_file->wrtPending); + cifsFileInfo_put(open_file); return rc; } diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h index 6084d63..e3b1161 100644 --- a/fs/cifs/cifsglob.h +++ b/fs/cifs/cifsglob.h @@ -351,11 +351,24 @@ struct cifsFileInfo { bool closePend:1; /* file is marked to close */ bool invalidHandle:1; /* file closed via session abend */ bool messageMode:1; /* for pipes: message vs byte mode */ - atomic_t wrtPending; /* handle in use - defer close */ + atomic_t count; /* reference count */ struct mutex fh_mutex; /* prevents reopen race after dead ses*/ struct cifs_search_info srch_inf; }; +/* Take a reference on the file private data */ +static inline void cifsFileInfo_get(struct cifsFileInfo *cifs_file) +{ + atomic_inc(&cifs_file->count); +} + +/* Release a reference on the file private data */ +static inline void cifsFileInfo_put(struct cifsFileInfo *cifs_file) +{ + if (atomic_dec_and_test(&cifs_file->count)) + kfree(cifs_file); +} + /* * One of these for each file inode */ diff --git a/fs/cifs/dir.c b/fs/cifs/dir.c index 4326ffd..a6424cf 100644 --- a/fs/cifs/dir.c +++ b/fs/cifs/dir.c @@ -153,7 +153,7 @@ cifs_fill_fileinfo(struct inode *newinode, __u16 fileHandle, mutex_init(&pCifsFile->fh_mutex); mutex_init(&pCifsFile->lock_mutex); INIT_LIST_HEAD(&pCifsFile->llist); - atomic_set(&pCifsFile->wrtPending, 0); + atomic_set(&pCifsFile->count, 1); /* set the following in open now pCifsFile->pfile = file; */ diff --git a/fs/cifs/file.c b/fs/cifs/file.c index c34b7f8..fa7beac 100644 --- a/fs/cifs/file.c +++ b/fs/cifs/file.c @@ -53,11 +53,9 @@ static inline struct cifsFileInfo *cifs_init_private( private_data->pInode = inode; private_data->invalidHandle = false; private_data->closePend = false; - /* we have to track num writers to the inode, since writepages - does not tell us which handle the write is for so there can - be a close (overlapping with write) of the filehandle that - cifs_writepages chose to use */ - atomic_set(&private_data->wrtPending, 0); + /* Initialize reference count to one. The private data is + freed on the release of the last reference */ + atomic_set(&private_data->count, 1); return private_data; } @@ -643,7 +641,7 @@ int cifs_close(struct inode *inode, struct file *file) if (!pTcon->need_reconnect) { write_unlock(&GlobalSMBSeslock); timeout = 2; - while ((atomic_read(&pSMBFile->wrtPending) != 0) + while ((atomic_read(&pSMBFile->count) != 1) && (timeout <= 2048)) { /* Give write a better chance to get to server ahead of the close. We do not @@ -657,8 +655,6 @@ int cifs_close(struct inode *inode, struct file *file) msleep(timeout); timeout *= 4; } - if (atomic_read(&pSMBFile->wrtPending)) - cERROR(1, ("close with pending write")); if (!pTcon->need_reconnect && !pSMBFile->invalidHandle) rc = CIFSSMBClose(xid, pTcon, @@ -681,24 +677,7 @@ int cifs_close(struct inode *inode, struct file *file) list_del(&pSMBFile->flist); list_del(&pSMBFile->tlist); write_unlock(&GlobalSMBSeslock); - timeout = 10; - /* We waited above to give the SMBWrite a chance to issue - on the wire (so we do not get SMBWrite returning EBADF - if writepages is racing with close. Note that writepages - does not specify a file handle, so it is possible for a file - to be opened twice, and the application close the "wrong" - file handle - in these cases we delay long enough to allow - the SMBWrite to get on the wire before the SMB Close. - We allow total wait here over 45 seconds, more than - oplock break time, and more than enough to allow any write - to complete on the server, or to time out on the client */ - while ((atomic_read(&pSMBFile->wrtPending) != 0) - && (timeout <= 50000)) { - cERROR(1, ("writes pending, delay free of handle")); - msleep(timeout); - timeout *= 8; - } - kfree(file->private_data); + cifsFileInfo_put(file->private_data); file->private_data = NULL; } else rc = -EBADF; @@ -1236,7 +1215,7 @@ struct cifsFileInfo *find_readable_file(struct cifsInodeInfo *cifs_inode) if (!open_file->invalidHandle) { /* found a good file */ /* lock it so it will not be closed on us */ - atomic_inc(&open_file->wrtPending); + cifsFileInfo_get(open_file); read_unlock(&GlobalSMBSeslock); return open_file; } /* else might as well continue, and look for @@ -1276,7 +1255,7 @@ refind_writable: if (open_file->pfile && ((open_file->pfile->f_flags & O_RDWR) || (open_file->pfile->f_flags & O_WRONLY))) { - atomic_inc(&open_file->wrtPending); + cifsFileInfo_get(open_file); if (!open_file->invalidHandle) { /* found a good writable file */ @@ -1293,7 +1272,7 @@ refind_writable: else { /* start over in case this was deleted */ /* since the list could be modified */ read_lock(&GlobalSMBSeslock); - atomic_dec(&open_file->wrtPending); + cifsFileInfo_put(open_file); goto refind_writable; } } @@ -1309,7 +1288,7 @@ refind_writable: read_lock(&GlobalSMBSeslock); /* can not use this handle, no write pending on this one after all */ - atomic_dec(&open_file->wrtPending); + cifsFileInfo_put(open_file); if (open_file->closePend) /* list could have changed */ goto refind_writable; @@ -1373,7 +1352,7 @@ static int cifs_partialpagewrite(struct page *page, unsigned from, unsigned to) if (open_file) { bytes_written = cifs_write(open_file->pfile, write_data, to-from, &offset); - atomic_dec(&open_file->wrtPending); + cifsFileInfo_put(open_file); /* Does mm or vfs already set times? */ inode->i_atime = inode->i_mtime = current_fs_time(inode->i_sb); if ((bytes_written > 0) && (offset)) @@ -1562,7 +1541,7 @@ retry: bytes_to_write, offset, &bytes_written, iov, n_iov, long_op); - atomic_dec(&open_file->wrtPending); + cifsFileInfo_put(open_file); cifs_update_eof(cifsi, offset, bytes_written); if (rc || bytes_written < bytes_to_write) { diff --git a/fs/cifs/inode.c b/fs/cifs/inode.c index 82d8383..1f09c76 100644 --- a/fs/cifs/inode.c +++ b/fs/cifs/inode.c @@ -800,7 +800,7 @@ set_via_filehandle: if (open_file == NULL) CIFSSMBClose(xid, pTcon, netfid); else - atomic_dec(&open_file->wrtPending); + cifsFileInfo_put(open_file); out: return rc; } @@ -1635,7 +1635,7 @@ cifs_set_file_size(struct inode *inode, struct iattr *attrs, __u32 npid = open_file->pid; rc = CIFSSMBSetFileSize(xid, pTcon, attrs->ia_size, nfid, npid, false); - atomic_dec(&open_file->wrtPending); + cifsFileInfo_put(open_file); cFYI(1, ("SetFSize for attrs rc = %d", rc)); if ((rc == -EINVAL) || (rc == -EOPNOTSUPP)) { unsigned int bytes_written; @@ -1790,7 +1790,7 @@ cifs_setattr_unix(struct dentry *direntry, struct iattr *attrs) u16 nfid = open_file->netfid; u32 npid = open_file->pid; rc = CIFSSMBUnixSetFileInfo(xid, pTcon, args, nfid, npid); - atomic_dec(&open_file->wrtPending); + cifsFileInfo_put(open_file); } else { rc = CIFSSMBUnixSetPathInfo(xid, pTcon, full_path, args, cifs_sb->local_nls,