Re: [PATCH v2 1/5] fs: rework getname_kernel to handle up to PATH_MAX sized filenames

Richard Guy Briggs
2015-01-22T15:53:16Z

On 15/01/21, Paul Moore wrote:
> In preparation for expanded use in the kernel, make getname_kernel()
> more useful by allowing it to handle any legal filename length.
>
> Thanks to Guenter Roeck for his suggestion to substitute memcpy() for
> strlcpy().
>
> CC: linux@roeck-us.net
> CC: viro@zeniv.linux.org.uk
> CC: linux-fsdevel@vger.kernel.org
> Signed-off-by: Paul Moore <pmoore@redhat.com>

Noted memcpy() difference (I assume to avoid races).

Reviewed-by: Richard Guy Briggs <rgb@redhat.com>

> ---
> fs/namei.c | 34 ++++++++++++++++++++--------------
> 1 file changed, 20 insertions(+), 14 deletions(-)
>
> diff --git a/fs/namei.c b/fs/namei.c
> index 9eb787e..63eaaf6 100644
> --- a/fs/namei.c
> +++ b/fs/namei.c
> @@ -211,32 +211,38 @@ getname(const char __user * filename)
> return getname_flags(filename, 0, NULL);
> }
>
> -/*
> - * The "getname_kernel()" interface doesn't do pathnames longer
> - * than EMBEDDED_NAME_MAX. Deal with it - you're a kernel user.
> - */
> struct filename *
> getname_kernel(const char * filename)
> {
> struct filename *result;
> - char *kname;
> - int len;
> -
> - len = strlen(filename);
> - if (len >= EMBEDDED_NAME_MAX)
> - return ERR_PTR(-ENAMETOOLONG);
> + int len = strlen(filename) + 1;
>
> result = __getname();
> if (unlikely(!result))
> return ERR_PTR(-ENOMEM);
>
> - kname = (char *)result + sizeof(*result);
> - result->name = kname;
> + if (len <= EMBEDDED_NAME_MAX) {
> + result->name = (char *)(result) + sizeof(*result);
> + result->separate = false;
> + } else if (len <= PATH_MAX) {
> + struct filename *tmp;
> +
> + tmp = kmalloc(sizeof(*tmp), GFP_KERNEL);
> + if (unlikely(!tmp)) {
> + __putname(result);
> + return ERR_PTR(-ENOMEM);
> + }
> + tmp->name = (char *)result;
> + tmp->separate = true;
> + result = tmp;
> + } else {
> + __putname(result);
> + return ERR_PTR(-ENAMETOOLONG);
> + }
> + memcpy((char *)result->name, filename, len);
> result->uptr = NULL;
> result->aname = NULL;
> - result->separate = false;
>
> - strlcpy(kname, filename, EMBEDDED_NAME_MAX);
> return result;
> }
>
>

- RGB

--
Richard Guy Briggs <rbriggs@redhat.com>
Senior Software Engineer, Kernel Security, AMER ENG Base Operating Systems, Red Hat
Remote, Ottawa, Canada
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