On 03/04/2019 13.17, Andy Shevchenko wrote: > On Wed, Apr 03, 2019 at 02:15:22PM +0300, Andy Shevchenko wrote: >> On Wed, Apr 03, 2019 at 07:45:36AM +0300, Yury Norov wrote: >>> Currently we parse user data byte after byte which leads to >>> overcomplification of parsing algorithm. The only user of >>> bitmap_parselist_user() is not performance-critical, and so we >>> can copy user data to kernel buffer and simply call >>> bitmap_parselist(). This rework lets us unify and simplify >>> bitmap_parselist() and bitmap_parselist_user(), which is done >>> in the following patch. >> >>> + buf = kmalloc(ulen + 1, GFP_KERNEL); >>> + if (!buf) >>> + return -ENOMEM; >>> + >>> + buf[ulen] = 0; >>> + >>> + ret = copy_from_user(buf, ubuf, ulen); >>> + if (ret) >>> + goto out; >> >> Why not memdup_user() ? > > Even more precisely (for strings) strndup_user(). >
But the user buffer is not nul-terminated, i.e. it's not a string. What you want is memdup_user_nul() - take a length-delimited user buffer and turn it into a nul-terminated string in kernel memory. And yes, please use that. Rasmus
