On Thu, Mar 14, 2024 at 10:29:37PM +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. > > @query is already marked as __nonstring and doesn't need to be > NUL-terminated. Due to this, we don't need to use a string API here > (especially a deprecated one). Let's have our stack allocation also > zero-initialize so that we can just perform a standard memcpy. Since the > code now speaks for itself we can drop the comment. A memcpy on a > __nonstring buffer explains everything that this comment talks about. > > 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@xxxxxxxxxxxxxxx > Signed-off-by: Justin Stitt <justinstitt@xxxxxxxxxx> > --- > Note: build-tested only. > > Found with: $ rg "strncpy\(" > --- > drivers/soc/qcom/cmd-db.c | 9 ++------- > 1 file changed, 2 insertions(+), 7 deletions(-) > > diff --git a/drivers/soc/qcom/cmd-db.c b/drivers/soc/qcom/cmd-db.c > index a5fd68411bed..512556366a3e 100644 > --- a/drivers/soc/qcom/cmd-db.c > +++ b/drivers/soc/qcom/cmd-db.c > @@ -141,18 +141,13 @@ static int cmd_db_get_header(const char *id, const struct entry_header **eh, > const struct rsc_hdr *rsc_hdr; > const struct entry_header *ent; > int ret, i, j; > - u8 query[sizeof(ent->id)] __nonstring; > + u8 query[sizeof(ent->id)] __nonstring = { 0 }; > > ret = cmd_db_ready(); > if (ret) > return ret; > > - /* > - * Pad out query string to same length as in DB. NOTE: the output > - * query string is not necessarily '\0' terminated if it bumps up > - * against the max size. That's OK and expected. > - */ > - strncpy(query, id, sizeof(query)); > + memcpy(query, id, sizeof(query)); Hm, no, this isn't right. We do want to stop copying at the first NUL character, but we don't care about truncation. e.g. imagine if "id" was a 3 character string followed by other bytes in memory. We'd copy beyond the end of "id" into query, and the later memcmp()s would start failing. I think what you want here is: strtomem(query, id); -Kees > > for (i = 0; i < MAX_SLV_ID; i++) { > rsc_hdr = &cmd_db_header->header[i]; > > --- > base-commit: fe46a7dd189e25604716c03576d05ac8a5209743 > change-id: 20240314-strncpy-drivers-soc-qcom-cmd-db-c-284f3abaabb8 > > Best regards, > -- > Justin Stitt <justinstitt@xxxxxxxxxx> > > -- Kees Cook
