Hi Al Viro,
On Tue, Aug 20, 2013 at 1:06 PM, Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote:
> On Tue, Aug 20, 2013 at 12:51:56PM +0530, Arun KS wrote:
>
>> d_path expects the pathname to be less than 64 bytes. If its more than
>> 64, it returns -ENAMETOOLONG.
>
> ?!?!? d_path() does not expect anything of that sort - it can very
> well produce names much longer, without ENAMETOOLONG.
>
>> char *dynamic_dname(struct dentry *dentry, char *buffer, int buflen,
>> const char *fmt, ...)
>> {
>> va_list args;
>> char temp[64];
>> int sz;
>>
>> va_start(args, fmt);
>> sz = vsnprintf(temp, sizeof(temp), fmt, args) + 1;
>> va_end(args);
>>
>> if (sz > sizeof(temp) || sz > buflen)
>> return ERR_PTR(-ENAMETOOLONG);
>>
>> buffer += buflen - sz;
>> return memcpy(buffer, temp, sz);
>> }
>
> Aha. _That_ is a bug, all right - dynamic_dname() is simply not suitable
> for that kind of uses. ashmem.c is certainly abusing shmem_file_setup();
> feeding that kind of mess as dentry name is a Bad Idea(tm). Anyway,
> I'd suggest this for a fix:
>
> va_list args;
> size_t sz;
> va_start(args, fmt);
> sz = vsnprintf(NULL, 0, fmt, args) + 1;
> va_end(args);
> if (sz > buflen)
> return ERR_PTR(-ENAMETOOLONG);
> va_start(args, fmt);
> buffer += buflen - sz;
> vsprintf(buffer, fmt, args);
> va_end(args);
> return buffer;
>
> Either right in dynamic_dname(), or as possibly_fucking_long_dname(),
> to be used by shmem.c...
This fixes the problem.
Thanks,
Arun
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