On February 21, 2024 4:41:52 PM PST, Justin Stitt <justinstitt@xxxxxxxxxx> 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 ae->value_string to be NUL-terminated because there's a >comment that says as much; these attr strings are also used with other >string APIs, further cementing the fact. > >Now, the question of whether or not to NUL-pad the destination buffer: >lpfc_fdmi_rprt_defer() initializes vports (all zero-initialized), then >we call lpfc_fdmi_cmd() with each vport and a mask. Then, inside of >lpfc_fdmi_cmd() we check each bit in the mask to invoke the proper >callback. Importantly, the zero-initialized vport is passed in as the >"attr" parameter. Seeing this: >| struct lpfc_fdmi_attr_string *ae = attr; >... we can tell that ae->value_string is entirely zero-initialized. Due >to this, NUL-padding is _not_ required as it would be redundant. > >Conveniently, strscpy also returns the number of bytes copied into the >destination buffer, eliminating the need for strnlen! > >Considering the above, a suitable replacement is `strscpy` [2]. > >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> >--- > drivers/scsi/lpfc/lpfc_ct.c | 5 ++--- > 1 file changed, 2 insertions(+), 3 deletions(-) > >diff --git a/drivers/scsi/lpfc/lpfc_ct.c b/drivers/scsi/lpfc/lpfc_ct.c >index baae1f8279e0..42594ec87290 100644 >--- a/drivers/scsi/lpfc/lpfc_ct.c >+++ b/drivers/scsi/lpfc/lpfc_ct.c >@@ -2569,9 +2569,8 @@ lpfc_fdmi_set_attr_string(void *attr, uint16_t attrtype, char *attrstring) > * 64 bytes or less. > */ > >- strncpy(ae->value_string, attrstring, sizeof(ae->value_string)); >- len = strnlen(ae->value_string, sizeof(ae->value_string)); >- /* round string length to a 32bit boundary. Ensure there's a NULL */ >+ len = strscpy(ae->value_string, attrstring, sizeof(ae->value_string)); This could be < 0 on error, and at least lpfc_fdmi_hba_attr_os_ver() may present more than 64 bytes... -Kees >+ /* round string length to a 32bit boundary */ > len += (len & 3) ? (4 - (len & 3)) : 4; > /* size is Type/Len (4 bytes) plus string length */ > size = FOURBYTES + len; > >--- >base-commit: 39133352cbed6626956d38ed72012f49b0421e7b >change-id: 20240222-strncpy-drivers-scsi-lpfc-lpfc_ct-c-f54b67eeeb68 > >Best regards, >-- >Justin Stitt <justinstitt@xxxxxxxxxx> > > -- Kees Cook
