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tracefs: Fix refcount imbalance in start_creating()

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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 190afd81e4 ("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.daniel@iogearbox.net

Fixes: 4282d60689 ("tracefs: Add new tracefs file system")
Cc: stable@vger.kernel.org # 4.1+
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
This commit is contained in:
Daniel Borkmann 2015-11-04 23:33:17 +01:00 committed by Steven Rostedt
parent 43ed384339
commit d227c3ae4e
1 changed files with 5 additions and 1 deletions
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6
fs/tracefs/inode.c
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@ -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;
}