On Tue, Dec 10, 2019 at 08:10:01PM +0800, Tiezhu Yang wrote:
> diff --git a/fs/crypto/fname.c b/fs/crypto/fname.c
> index 3da3707..ef7eba8 100644
> --- a/fs/crypto/fname.c
> +++ b/fs/crypto/fname.c
> @@ -11,21 +11,11 @@
> * This has not yet undergone a rigorous security audit.
> */
>
> +#include <linux/namei.h>
> #include <linux/scatterlist.h>
> #include <crypto/skcipher.h>
> #include "fscrypt_private.h"
>
> -static inline bool fscrypt_is_dot_dotdot(const struct qstr *str)
> -{
> - if (str->len == 1 && str->name[0] == '.')
> - return true;
> -
> - if (str->len == 2 && str->name[0] == '.' && str->name[1] == '.')
> - return true;
> -
> - return false;
> -}
> -
> /**
> * fname_encrypt() - encrypt a filename
> *
> @@ -255,7 +245,7 @@ int fscrypt_fname_disk_to_usr(struct inode *inode,
> const struct qstr qname = FSTR_TO_QSTR(iname);
> struct fscrypt_digested_name digested_name;
>
> - if (fscrypt_is_dot_dotdot(&qname)) {
> + if (is_dot_or_dotdot(qname.name, qname.len)) {
There's no need for the 'qname' variable anymore. Can you please remove it and
do:
if (is_dot_or_dotdot(iname->name, iname->len)) {
> diff --git a/include/linux/namei.h b/include/linux/namei.h
> index 7fe7b87..aba114a 100644
> --- a/include/linux/namei.h
> +++ b/include/linux/namei.h
> @@ -92,4 +92,14 @@ retry_estale(const long error, const unsigned int flags)
> return error == -ESTALE && !(flags & LOOKUP_REVAL);
> }
>
> +static inline bool is_dot_or_dotdot(const unsigned char *name, size_t len)
> +{
> + if (unlikely(name[0] == '.')) {
> + if (len < 2 || (len == 2 && name[1] == '.'))
> + return true;
> + }
> +
> + return false;
> +}
This doesn't handle the len=0 case. Did you check that none of the users pass
in zero-length names? It looks like fscrypt_fname_disk_to_usr() can, if the
directory entry on-disk has a zero-length name. Currently it will return
-EUCLEAN in that case, but with this patch it may think it's the name ".".
So I think there needs to either be a len >= 1 check added, *or* you need to
make an argument for why it's okay to not care about the empty name case.
- Eric
