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SubjectRe: [PATCH v4] fs: introduce is_dot_or_dotdot helper for cleanup
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On 12/11/2019 03:19 AM, Eric Biggers wrote:
> 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)) {

Hi Eric,

Thanks for your review, I will do it in the v5 patch.

>
>> 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.

Anyway, let me modify the if condition "len < 2" to "len == 1".

static inline bool is_dot_or_dotdot(const unsigned char *name, size_t len)
{
if (unlikely(name[0] == '.')) {
if (len == 1 || (len == 2 && name[1] == '.'))
return true;
}

return false;
}

I will send v5 patch as soon as possible.

Thanks,

Tiezhu Yang

>
> - Eric

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