Forgot to Cc Daniel.
-- Steve
On Thu, 5 Nov 2015 08:29:33 -0500
Steven Rostedt <rost...@goodmis.org> wrote:
> git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace.git
> for-next
>
> Head SHA1: d227c3ae4e94e5eb11dd780a811f59e1a7b74ccd
>
>
> Daniel Borkmann (1):
> tracefs: Fix refcount imbalance in start_creating()
>
> ----
> fs/tracefs/inode.c | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
> ---------------------------
> commit d227c3ae4e94e5eb11dd780a811f59e1a7b74ccd
> Author: Daniel Borkmann <dan...@iogearbox.net>
> Date: Wed Nov 4 23:33:17 2015 +0100
>
> tracefs: Fix refcount imbalance in start_creating()
>
> In tracefs' start_creating(), we pin the file system to safely access
> its root. When we failed to create a file, we unpin the file system via
> failed_creating() to release the mount count and eventually the reference
> of the singleton vfsmount.
>
> However, when we run into an error during lookup_one_len() when still
> in start_creating(), we only release the parent's mutex but not so the
> reference on the mount.
>
> F.e., in securityfs_create_file(), after doing simple_pin_fs() when
> lookup_one_len() fails there, we infact do simple_release_fs(). This
> seems necessary here as well.
>
> Same issue seen in debugfs due to 190afd81e4a5 ("debugfs: split the
> beginning and the end of __create_file() off"), which seemed to got
> carried over into tracefs, too. Noticed during code review.
>
> Link:
> http://lkml.kernel.org/r/68efa86101b778cf7517ed7c6ad573bd69f60ec6.1446672850.git.dan...@iogearbox.net
>
> Fixes: 4282d60689d4 ("tracefs: Add new tracefs file system")
> Cc: sta...@vger.kernel.org # 4.1+
> Signed-off-by: Daniel Borkmann <dan...@iogearbox.net>
> Signed-off-by: Steven Rostedt <rost...@goodmis.org>
>
> diff --git a/fs/tracefs/inode.c b/fs/tracefs/inode.c
> index cbc8d5d2755a..c66f2423e1f5 100644
> --- a/fs/tracefs/inode.c
> +++ b/fs/tracefs/inode.c
> @@ -340,8 +340,12 @@ static struct dentry *start_creating(const char *name,
> struct dentry *parent)
> dput(dentry);
> dentry = ERR_PTR(-EEXIST);
> }
> - if (IS_ERR(dentry))
> +
> + if (IS_ERR(dentry)) {
> mutex_unlock(&parent->d_inode->i_mutex);
> + simple_release_fs(&tracefs_mount, &tracefs_mount_count);
> + }
> +
> return dentry;
> }
>
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