| Message ID | 20231003-strncpy-drivers-hid-uhid-c-v2-1-6a501402581e@google.com (mailing list archive) |
|---|---|
| State | New |
| Delegated to: | Jiri Kosina |
| Headers | show |
| Series | [v2] HID: uhid: replace deprecated strncpy with strscpy | expand |
On Tue, Oct 03, 2023 at 09:01:58PM +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. > > A suitable replacement is `strscpy` [2] due to the fact that it > guarantees NUL-termination on the destination buffer without > unnecessarily NUL-padding. > > Furthermore, let's make sure `hid->xyz` and `ev->u.create2.xyz` are the > same size at compile time to prevent silent truncation. > > With these changes, it is abundantly clear what the intent and behavior > of the code is -- We are getting a string to string copy with > NUL-termination and no truncation. > > 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 > Cc: Kees Cook <keescook@chromium.org> > Signed-off-by: Justin Stitt <justinstitt@google.com> Great! This looks much simpler to me. Thanks for adjusting it. Reviewed-by: Kees Cook <keescook@chromium.org>
On Tue, 03 Oct 2023 21:01:58 +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. > > A suitable replacement is `strscpy` [2] due to the fact that it > guarantees NUL-termination on the destination buffer without > unnecessarily NUL-padding. > > [...] Applied to for-next/hardening, thanks! [1/1] HID: uhid: replace deprecated strncpy with strscpy https://git.kernel.org/kees/c/d4011f6817ae Take care,
diff --git a/drivers/hid/uhid.c b/drivers/hid/uhid.c index 4588d2cd4ea4..a54c7995b9be 100644 --- a/drivers/hid/uhid.c +++ b/drivers/hid/uhid.c @@ -490,7 +490,7 @@ static int uhid_dev_create2(struct uhid_device *uhid, const struct uhid_event *ev) { struct hid_device *hid; - size_t rd_size, len; + size_t rd_size; void *rd_data; int ret; @@ -514,13 +514,12 @@ static int uhid_dev_create2(struct uhid_device *uhid, goto err_free; } - /* @hid is zero-initialized, strncpy() is correct, strlcpy() not */ - len = min(sizeof(hid->name), sizeof(ev->u.create2.name)) - 1; - strncpy(hid->name, ev->u.create2.name, len); - len = min(sizeof(hid->phys), sizeof(ev->u.create2.phys)) - 1; - strncpy(hid->phys, ev->u.create2.phys, len); - len = min(sizeof(hid->uniq), sizeof(ev->u.create2.uniq)) - 1; - strncpy(hid->uniq, ev->u.create2.uniq, len); + BUILD_BUG_ON(sizeof(hid->name) != sizeof(ev->u.create2.name)); + strscpy(hid->name, ev->u.create2.name, sizeof(hid->name)); + BUILD_BUG_ON(sizeof(hid->phys) != sizeof(ev->u.create2.phys)); + strscpy(hid->phys, ev->u.create2.phys, sizeof(hid->phys)); + BUILD_BUG_ON(sizeof(hid->uniq) != sizeof(ev->u.create2.uniq)); + strscpy(hid->uniq, ev->u.create2.uniq, sizeof(hid->uniq)); hid->ll_driver = &uhid_hid_driver; hid->bus = ev->u.create2.bus;
`strncpy` is deprecated for use on NUL-terminated destination strings [1] and as such we should prefer more robust and less ambiguous string interfaces. A suitable replacement is `strscpy` [2] due to the fact that it guarantees NUL-termination on the destination buffer without unnecessarily NUL-padding. Furthermore, let's make sure `hid->xyz` and `ev->u.create2.xyz` are the same size at compile time to prevent silent truncation. With these changes, it is abundantly clear what the intent and behavior of the code is -- We are getting a string to string copy with NUL-termination and no truncation. 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 Cc: Kees Cook <keescook@chromium.org> Signed-off-by: Justin Stitt <justinstitt@google.com> --- Changes in v2: - update subject + commit message (thanks Kees) - use BUILD_BUG_ON size mismatch (thanks Kees and David) - Link to v1: https://lore.kernel.org/r/20230914-strncpy-drivers-hid-uhid-c-v1-1-18a190060d8d@google.com --- drivers/hid/uhid.c | 15 +++++++-------- 1 file changed, 7 insertions(+), 8 deletions(-) --- base-commit: 3669558bdf354cd352be955ef2764cde6a9bf5ec change-id: 20230914-strncpy-drivers-hid-uhid-c-a465f3e784dd Best regards, -- Justin Stitt <justinstitt@google.com>