From 50cbdaf1b93a2cc89d7712feafa76cf1b2f28adc Mon Sep 17 00:00:00 2001 From: Justin Stitt Date: Thu, 19 Oct 2023 23:28:32 +0000 Subject: PNP: replace deprecated strncpy() with memcpy() 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 Signed-off-by: Justin Stitt Reviewed-by: Kees Cook Signed-off-by: Rafael J. Wysocki --- drivers/pnp/pnpbios/rsparser.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) 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; -- cgit v1.2.3