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Wysocki" Cc: linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org, Justin Stitt X-Spam-Status: No, score=-8.4 required=5.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL autolearn=unavailable autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on groat.vger.email Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-Greylist: Sender passed SPF test, not delayed by milter-greylist-4.6.4 (groat.vger.email [0.0.0.0]); Thu, 19 Oct 2023 16:28:47 -0700 (PDT) X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1780228429582739382 X-GMAIL-MSGID: 1780228429582739382 strncpy() is deprecated for use on NUL-terminated destination strings [1] and as such we should prefer more robust and less ambiguous interfaces. After having precisely calculated the lengths and ensuring we don't overflow the buffer, this really decays to just a memcpy. Let's not use a C string api as it makes the intention of the code confusing. It'd be nice to use strscpy() in this case (as we clearly want NUL-termination) because it'd clean up the code a bit. However, I don't quite know enough about what is going on here to justify a drop-in replacement -- too much bit magic and why (PNP_NAME_LEN - 2)? I'm afraid using strscpy() may result in copying too many or too few bytes into our dev->name buffer resulting in different behavior. At least using memcpy() we can ensure the behavior is exactly the same. Side note: NUL-padding is not required because insert_device() calls pnpbios_parse_data_stream() with a zero-allocated `dev`: 299 | static int __init insert_device(struct pnp_bios_node *node) { ... 312 | dev = pnp_alloc_dev(&pnpbios_protocol, node->handle, id); ... 316 | pnpbios_parse_data_stream(dev, node); then pnpbios_parse_data_stream() calls pnpbios_parse_compatible_ids(). Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1] Link: https://github.com/KSPP/linux/issues/90 Cc: linux-hardening@vger.kernel.org Signed-off-by: Justin Stitt Reviewed-by: Kees Cook --- Note: build-tested only. Found with: $ rg "strncpy\(" --- drivers/pnp/pnpbios/rsparser.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- base-commit: dab3e01664eaddae965699f1fec776609db0ea9d change-id: 20231019-strncpy-drivers-pnp-pnpbios-rsparser-c-5d7343441cac Best regards, -- Justin Stitt diff --git a/drivers/pnp/pnpbios/rsparser.c b/drivers/pnp/pnpbios/rsparser.c index 2f31b212b1a5..70af7821d3fa 100644 --- a/drivers/pnp/pnpbios/rsparser.c +++ b/drivers/pnp/pnpbios/rsparser.c @@ -454,8 +454,8 @@ static unsigned char *pnpbios_parse_compatible_ids(unsigned char *p, switch (tag) { case LARGE_TAG_ANSISTR: - strncpy(dev->name, p + 3, - len >= PNP_NAME_LEN ? PNP_NAME_LEN - 2 : len); + memcpy(dev->name, p + 3, + len >= PNP_NAME_LEN ? PNP_NAME_LEN - 2 : len); dev->name[len >= PNP_NAME_LEN ? PNP_NAME_LEN - 1 : len] = '\0'; break;