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: [email protected]
Signed-off-by: Justin Stitt <[email protected]>
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(-)
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;
---
base-commit: dab3e01664eaddae965699f1fec776609db0ea9d
change-id: 20231019-strncpy-drivers-nvme-host-fc-c-a542b34b8710
Best regards,
--
Justin Stitt <[email protected]>
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: [email protected]
> Signed-off-by: Justin Stitt <[email protected]>
> Similar-to: https://lore.kernel.org/all/20231018-strncpy-drivers-nvme-host-fabrics-c-v1-1-b6677df40a35@google.com/
Reviewed-by: Kees Cook <[email protected]>
--
Kees Cook
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,
--
Kees Cook