On Wed, Aug 26, 2020 at 07:42:17PM -0700, Joe Perches wrote: > On Wed, 2020-08-26 at 19:33 -0700, Kees Cook wrote: > > On Wed, Aug 26, 2020 at 04:57:41PM -0700, Joe Perches wrote: > > > On Wed, 2020-08-26 at 16:38 -0700, Kees Cook wrote: > > > > On Thu, Aug 27, 2020 at 07:59:45AM +0900, Masahiro Yamada wrote: > > > [] > > > > > OK, then stpcpy(), strcpy() and sprintf() > > > > > have the same level of unsafety. > > > > > > > > Yes. And even snprintf() is dangerous because its return value is how > > > > much it WOULD have written, which when (commonly) used as an offset for > > > > further pointer writes, causes OOB writes too. :( > > > > https://github.com/KSPP/linux/issues/105 > > > > > > > > > strcpy() is used everywhere. > > > > > > > > Yes. It's very frustrating, but it's not an excuse to continue > > > > using it nor introducing more bad APIs. > > > > > > > > $ git grep '\bstrcpy\b' | wc -l > > > > 2212 > > > > $ git grep '\bstrncpy\b' | wc -l > > > > 751 > > > > $ git grep '\bstrlcpy\b' | wc -l > > > > 1712 > > > > > > > > $ git grep '\bstrscpy\b' | wc -l > > > > 1066 > > > > > > > > https://www.kernel.org/doc/html/latest/process/deprecated.html#strcpy > > > > https://github.com/KSPP/linux/issues/88 > > > > > > > > https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings > > > > https://github.com/KSPP/linux/issues/89 > > > > > > > > https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy > > > > https://github.com/KSPP/linux/issues/90 > > > > > > > > We have no way right now to block the addition of deprecated API usage, > > > > which makes ever catching up on this replacement very challenging. > > > > > > These could be added to checkpatch's deprecated_api test. > > > --- > > > scripts/checkpatch.pl | 3 +++ > > > 1 file changed, 3 insertions(+) > > > > > > diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl > > > index 149518d2a6a7..f9ccb2a63a95 100755 > > > --- a/scripts/checkpatch.pl > > > +++ b/scripts/checkpatch.pl > > > @@ -605,6 +605,9 @@ foreach my $entry (@mode_permission_funcs) { > > > $mode_perms_search = "(?:${mode_perms_search})"; > > > > > > our %deprecated_apis = ( > > > + "strcpy" => "strscpy", > > > + "strncpy" => "strscpy", > > > + "strlcpy" => "strscpy", > > > "synchronize_rcu_bh" => "synchronize_rcu", > > > "synchronize_rcu_bh_expedited" => "synchronize_rcu_expedited", > > > "call_rcu_bh" => "call_rcu", > > > > > > > > > > Good idea, yeah. We, unfortunately, need to leave strncpy() off this > > list for now because it's not *strictly* deprecated (see the notes in > > bug report[1]), but the others can be. > > OK, but it is in Documentation/process/deprecated.rst > > strncpy() on NUL-terminated strings "... on NUL-terminated strings". It's "valid" to use it on known-size (either external or by definition) NUL-padded buffers (e.g. NLA_STRING). -- Kees Cook
