APPLIED: [SRU][Trusty][CVE-2017-18204][PATCH] ocfs2: should wait dio before inode lock in ocfs2_setattr()

[Stefan Bader]

On 19.04.2018 18:32, Kleber Sacilotto de Souza wrote:
> From: alex chen <alex.chen at huawei.com>
> 
> CVE-2017-18204
> 
> we should wait dio requests to finish before inode lock in
> ocfs2_setattr(), otherwise the following deadlock will happen:
> 
> process 1                  process 2                    process 3
> truncate file 'A'          end_io of writing file 'A'   receiving the bast messages
> ocfs2_setattr
>  ocfs2_inode_lock_tracker
>   ocfs2_inode_lock_full
>  inode_dio_wait
>   __inode_dio_wait
>   -->waiting for all dio
>   requests finish
>                                                         dlm_proxy_ast_handler
>                                                          dlm_do_local_bast
>                                                           ocfs2_blocking_ast
>                                                            ocfs2_generic_handle_bast
>                                                             set OCFS2_LOCK_BLOCKED flag
>                         dio_end_io
>                          dio_bio_end_aio
>                           dio_complete
>                            ocfs2_dio_end_io
>                             ocfs2_dio_end_io_write
>                              ocfs2_inode_lock
>                               __ocfs2_cluster_lock
>                                ocfs2_wait_for_mask
>                                -->waiting for OCFS2_LOCK_BLOCKED
>                                flag to be cleared, that is waiting
>                                for 'process 1' unlocking the inode lock
>                            inode_dio_end
>                            -->here dec the i_dio_count, but will never
>                            be called, so a deadlock happened.
> 
> Link: http://lkml.kernel.org/r/59F81636.70508@huawei.com
> Signed-off-by: Alex Chen <alex.chen at huawei.com>
> Reviewed-by: Jun Piao <piaojun at huawei.com>
> Reviewed-by: Joseph Qi <jiangqi903 at gmail.com>
> Acked-by: Changwei Ge <ge.changwei at h3c.com>
> Cc: Mark Fasheh <mfasheh at versity.com>
> Cc: Joel Becker <jlbec at evilplan.org>
> Cc: Junxiao Bi <junxiao.bi at oracle.com>
> Cc: <stable at vger.kernel.org>
> Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
> Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
> (backported from commit 28f5a8a7c033cbf3e32277f4cc9c6afd74f05300)
> [ klebers: adjusted for context. ]
> Signed-off-by: Kleber Sacilotto de Souza <kleber.souza at canonical.com>
> ---

Applied to trusty/master-next

>  fs/ocfs2/file.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/ocfs2/file.c b/fs/ocfs2/file.c
> index 7f4733187958..79e2fbd1db23 100644
> --- a/fs/ocfs2/file.c
> +++ b/fs/ocfs2/file.c
> @@ -1131,6 +1131,13 @@ int ocfs2_setattr(struct dentry *dentry, struct iattr *attr)
>  		dquot_initialize(inode);
>  	size_change = S_ISREG(inode->i_mode) && attr->ia_valid & ATTR_SIZE;
>  	if (size_change) {
> +		/*
> +		 * Here we should wait dio to finish before inode lock
> +		 * to avoid a deadlock between ocfs2_setattr() and
> +		 * ocfs2_dio_end_io_write()
> +		 */
> +		inode_dio_wait(inode);
> +
>  		status = ocfs2_rw_lock(inode, 1);
>  		if (status < 0) {
>  			mlog_errno(status);
> @@ -1150,8 +1157,6 @@ int ocfs2_setattr(struct dentry *dentry, struct iattr *attr)
>  		if (status)
>  			goto bail_unlock;
>  
> -		inode_dio_wait(inode);
> -
>  		if (i_size_read(inode) > attr->ia_size) {
>  			if (ocfs2_should_order_data(inode)) {
>  				status = ocfs2_begin_ordered_truncate(inode,
> 


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