| Message ID | 20240318-strncpy-drivers-tty-n_gsm-c-v1-1-da37a07c642e@google.com |
|---|---|
| State | New |
| Headers | show |
| Series | tty: n_gsm: replace deprecated strncpy with strscpy | expand |
Hi Justin, > --- > Note: build-tested only. Really? Without warnings? > --- a/drivers/tty/n_gsm.c > +++ b/drivers/tty/n_gsm.c > @@ -4010,7 +4010,7 @@ static int gsm_create_network(struct gsm_dlci *dlci, > struct gsm_netconfig *nc) > mux_net = netdev_priv(net); > mux_net->dlci = dlci; > kref_init(&mux_net->ref); > - strncpy(nc->if_name, net->name, IFNAMSIZ); /* return net name */ > + strscpy(nc->if_name, net->name); /* return net name */ Where did IFNAMSIZ go? Kind regards, Maarten Brock
Hi, On Tue, Mar 19, 2024 at 2:11 AM Maarten Brock <Maarten.Brock@sttls.nl> wrote: > > Hi Justin, > > > --- > > Note: build-tested only. > > Really? Without warnings? > > > --- a/drivers/tty/n_gsm.c > > +++ b/drivers/tty/n_gsm.c > > @@ -4010,7 +4010,7 @@ static int gsm_create_network(struct gsm_dlci *dlci, > > struct gsm_netconfig *nc) > > mux_net = netdev_priv(net); > > mux_net->dlci = dlci; > > kref_init(&mux_net->ref); > > - strncpy(nc->if_name, net->name, IFNAMSIZ); /* return net name */ > > + strscpy(nc->if_name, net->name); /* return net name */ > > Where did IFNAMSIZ go? There's a new 2-argument strscpy introduced in Commit e6584c3964f2f ("string: Allow 2-argument strscpy()"). Since the compiler can find nc->if_name's size (which is == IFNAMSIZ) it should be A-OK to swap to this new form. > > Kind regards, > Maarten Brock > Thanks Justin
On Mon, Mar 18, 2024 at 11:02:12PM +0000, Justin Stitt wrote: > strncpy() is deprecated for use on NUL-terminated destination strings > [1] and as such we should prefer more robust and less ambiguous string > interfaces. > > We expect nc->if_name to be NUL-terminated based on existing manual > NUL-byte assignments and checks: > | nc.if_name[IFNAMSIZ-1] = '\0'; > ... > | if (nc->if_name[0] != '\0') > > Let's use the new 2-argument strscpy() since it guarantees > NUL-termination on the destination buffer while correctly using the > destination buffers size to bound the operation. We may need for -rc1 (or -rc2), depending on when subsystem tree re-open for landing patches to use the 2-arg versio, but, regardless, it looks right: Reviewed-by: Kees Cook <keescook@chromium.org> -Kees > > Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1] > Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html [2] > Link: https://github.com/KSPP/linux/issues/90 > Cc: linux-hardening@vger.kernel.org > Signed-off-by: Justin Stitt <justinstitt@google.com> > --- > Note: build-tested only. > > Found with: $ rg "strncpy\(" > --- > drivers/tty/n_gsm.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c > index 4036566febcb..f5b0d91d32a7 100644 > --- a/drivers/tty/n_gsm.c > +++ b/drivers/tty/n_gsm.c > @@ -4010,7 +4010,7 @@ static int gsm_create_network(struct gsm_dlci *dlci, struct gsm_netconfig *nc) > mux_net = netdev_priv(net); > mux_net->dlci = dlci; > kref_init(&mux_net->ref); > - strncpy(nc->if_name, net->name, IFNAMSIZ); /* return net name */ > + strscpy(nc->if_name, net->name); /* return net name */ > > /* reconfigure dlci for network */ > dlci->prev_adaption = dlci->adaption; > > --- > base-commit: bf3a69c6861ff4dc7892d895c87074af7bc1c400 > change-id: 20240318-strncpy-drivers-tty-n_gsm-c-ab1336e0e196 > > Best regards, > -- > Justin Stitt <justinstitt@google.com> > >
diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c index 4036566febcb..f5b0d91d32a7 100644 --- a/drivers/tty/n_gsm.c +++ b/drivers/tty/n_gsm.c @@ -4010,7 +4010,7 @@ static int gsm_create_network(struct gsm_dlci *dlci, struct gsm_netconfig *nc) mux_net = netdev_priv(net); mux_net->dlci = dlci; kref_init(&mux_net->ref); - strncpy(nc->if_name, net->name, IFNAMSIZ); /* return net name */ + strscpy(nc->if_name, net->name); /* return net name */ /* reconfigure dlci for network */ dlci->prev_adaption = dlci->adaption;
strncpy() is deprecated for use on NUL-terminated destination strings [1] and as such we should prefer more robust and less ambiguous string interfaces. We expect nc->if_name to be NUL-terminated based on existing manual NUL-byte assignments and checks: | nc.if_name[IFNAMSIZ-1] = '\0'; ... | if (nc->if_name[0] != '\0') Let's use the new 2-argument strscpy() since it guarantees NUL-termination on the destination buffer while correctly using the destination buffers size to bound the operation. Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1] Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html [2] Link: https://github.com/KSPP/linux/issues/90 Cc: linux-hardening@vger.kernel.org Signed-off-by: Justin Stitt <justinstitt@google.com> --- Note: build-tested only. Found with: $ rg "strncpy\(" --- drivers/tty/n_gsm.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- base-commit: bf3a69c6861ff4dc7892d895c87074af7bc1c400 change-id: 20240318-strncpy-drivers-tty-n_gsm-c-ab1336e0e196 Best regards, -- Justin Stitt <justinstitt@google.com>