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debugfs: fix refcount imbalance in start_creating

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In debugfs' 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 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. Looks like it was done in the past, but after
splitting portions of __create_file() into start_creating() and
end_creating() via 190afd81e4 ("debugfs: split the beginning and the
end of __create_file() off"), this seemed missed. Noticed during code
review.

Fixes: 190afd81e4 ("debugfs: split the beginning and the end of __create_file() off")
Cc: stable@vger.kernel.org # v4.0+
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Daniel Borkmann 2015-11-05 00:01:51 +01:00 committed by Al Viro
parent ce5c2d2c25
commit 0ee9608c89
1 changed files with 5 additions and 1 deletions
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6
fs/debugfs/inode.c
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@ -271,8 +271,12 @@ 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(&d_inode(parent)->i_mutex);
simple_release_fs(&debugfs_mount, &debugfs_mount_count);
}
return dentry;
}