| Message ID | 20231019-strncpy-drivers-nvme-host-fc-c-v1-1-5805c15e4b49@google.com (mailing list archive) |
|---|---|
| State | Mainlined |
| Commit | e5a4975ca463e91c2009f5950e0156f0b857eb10 |
| Headers | show |
| Series | nvme-fc: replace deprecated strncpy with strscpy | expand |
On Thu, Oct 19, 2023 at 09:34:35PM +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. > > Let's instead use strscpy() [2] as it guarantees NUL-termination on the > destination buffer. > > Moreover, there is no need to use: > > | min(FCNVME_ASSOC_HOSTNQN_LEN, NVMF_NQN_SIZE)); > > I imagine this was originally done to make sure the destination buffer > is NUL-terminated by ensuring we copy a number of bytes less than the > size of our destination, thus leaving some NUL-bytes at the end. Yeah, this is odd, but I agree that the resulting strscpy does the intended copy, since we've seen that other nqn strings are expected to be %NUL terminated. > > However, with strscpy(), we no longer need to do this and we can instead > opt for the more idiomatic strscpy() usage of: > > | strscpy(dest, src, sizeof(dest)) > > Also, no NUL-padding is required as lsop is zero-allocated: > > | lsop = kzalloc((sizeof(*lsop) + > | sizeof(*assoc_rqst) + sizeof(*assoc_acc) + > | ctrl->lport->ops->lsrqst_priv_sz), GFP_KERNEL); > > ... and assoc_rqst points to a field in lsop: > > | assoc_rqst = (struct fcnvme_ls_cr_assoc_rqst *)&lsop[1]; > > Therefore, any additional NUL-byte assignments (like the ones that > strncpy() makes) are redundant. > > 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 > Signed-off-by: Justin Stitt <justinstitt@google.com> > Similar-to: https://lore.kernel.org/all/20231018-strncpy-drivers-nvme-host-fabrics-c-v1-1-b6677df40a35@google.com/ Reviewed-by: Kees Cook <keescook@chromium.org>
On Thu, 19 Oct 2023 21:34:35 +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. > > Let's instead use strscpy() [2] as it guarantees NUL-termination on the > destination buffer. > > [...] Applied to for-next/hardening, thanks! [1/1] nvme-fc: replace deprecated strncpy with strscpy https://git.kernel.org/kees/c/f62cacf390b7 Take care,
diff --git a/drivers/nvme/host/fc.c b/drivers/nvme/host/fc.c index a15b37750d6e..680585253f7c 100644 --- a/drivers/nvme/host/fc.c +++ b/drivers/nvme/host/fc.c @@ -1218,10 +1218,10 @@ nvme_fc_connect_admin_queue(struct nvme_fc_ctrl *ctrl, /* Linux supports only Dynamic controllers */ assoc_rqst->assoc_cmd.cntlid = cpu_to_be16(0xffff); uuid_copy(&assoc_rqst->assoc_cmd.hostid, &ctrl->ctrl.opts->host->id); - strncpy(assoc_rqst->assoc_cmd.hostnqn, ctrl->ctrl.opts->host->nqn, - min(FCNVME_ASSOC_HOSTNQN_LEN, NVMF_NQN_SIZE)); - strncpy(assoc_rqst->assoc_cmd.subnqn, ctrl->ctrl.opts->subsysnqn, - min(FCNVME_ASSOC_SUBNQN_LEN, NVMF_NQN_SIZE)); + strscpy(assoc_rqst->assoc_cmd.hostnqn, ctrl->ctrl.opts->host->nqn, + sizeof(assoc_rqst->assoc_cmd.hostnqn)); + strscpy(assoc_rqst->assoc_cmd.subnqn, ctrl->ctrl.opts->subsysnqn, + sizeof(assoc_rqst->assoc_cmd.subnqn)); lsop->queue = queue; lsreq->rqstaddr = assoc_rqst;
strncpy() is deprecated for use on NUL-terminated destination strings [1] and as such we should prefer more robust and less ambiguous string interfaces. Let's instead use strscpy() [2] as it guarantees NUL-termination on the destination buffer. Moreover, there is no need to use: | min(FCNVME_ASSOC_HOSTNQN_LEN, NVMF_NQN_SIZE)); I imagine this was originally done to make sure the destination buffer is NUL-terminated by ensuring we copy a number of bytes less than the size of our destination, thus leaving some NUL-bytes at the end. However, with strscpy(), we no longer need to do this and we can instead opt for the more idiomatic strscpy() usage of: | strscpy(dest, src, sizeof(dest)) Also, no NUL-padding is required as lsop is zero-allocated: | lsop = kzalloc((sizeof(*lsop) + | sizeof(*assoc_rqst) + sizeof(*assoc_acc) + | ctrl->lport->ops->lsrqst_priv_sz), GFP_KERNEL); ... and assoc_rqst points to a field in lsop: | assoc_rqst = (struct fcnvme_ls_cr_assoc_rqst *)&lsop[1]; Therefore, any additional NUL-byte assignments (like the ones that strncpy() makes) are redundant. 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 Signed-off-by: Justin Stitt <justinstitt@google.com> Similar-to: https://lore.kernel.org/all/20231018-strncpy-drivers-nvme-host-fabrics-c-v1-1-b6677df40a35@google.com/ --- Note: build-tested only. --- drivers/nvme/host/fc.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) --- base-commit: dab3e01664eaddae965699f1fec776609db0ea9d change-id: 20231019-strncpy-drivers-nvme-host-fc-c-a542b34b8710 Best regards, -- Justin Stitt <justinstitt@google.com>