Re: [PATCH] scsi: ibmvfc: replace deprecated strncpy with strscpy
From: Kees Cook <hidden>
Date: 2023-11-30 21:12:53
Also in:
linux-hardening, linux-scsi, lkml
On Mon, Oct 30, 2023 at 07:04:33PM +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. We expect these fields to be NUL-terminated as the property names from which they are derived are also NUL-terminated. Moreover, NUL-padding is not required as our destination buffers are already NUL-allocated and any future NUL-byte assignments are redundant (like the ones that strncpy() does). ibmvfc_probe() -> | struct ibmvfc_host *vhost; | struct Scsi_Host *shost; ... | shost = scsi_host_alloc(&driver_template, sizeof(*vhost)); ... **side note: is this a bug? Looks like a type to me ^^^^^**
I think this is the "privsize", so *vhost is correct, IIUC.
... | vhost = shost_priv(shost);
I.e. vhost is a part of the shost allocation
... where shost_priv() is:
| static inline void *shost_priv(struct Scsi_Host *shost)
| {
| return (void *)shost->hostdata;
| }
.. and:
scsi_host_alloc() ->
| shost = kzalloc(sizeof(struct Scsi_Host) + privsize, GFP_KERNEL);As seen here. :)
And for login_info->..., NUL-padding is also not required as it is explicitly memset to 0: | memset(login_info, 0, sizeof(*login_info)); Considering the above, a suitable replacement is `strscpy` [2] due to the fact that it guarantees NUL-termination on the destination buffer without unnecessarily NUL-padding. 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>
Yeah, this conversion looks correct to me too. Reviewed-by: Kees Cook <redacted> -Kees
quoted hunk ↗ jump to hunk
--- Note: build-tested only. Found with: $ rg "strncpy\(" --- drivers/scsi/ibmvscsi/ibmvfc.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-)diff --git a/drivers/scsi/ibmvscsi/ibmvfc.c b/drivers/scsi/ibmvscsi/ibmvfc.c index ce9eb00e2ca0..e73a39b1c832 100644 --- a/drivers/scsi/ibmvscsi/ibmvfc.c +++ b/drivers/scsi/ibmvscsi/ibmvfc.c@@ -1455,7 +1455,7 @@ static void ibmvfc_gather_partition_info(struct ibmvfc_host *vhost) name = of_get_property(rootdn, "ibm,partition-name", NULL); if (name) - strncpy(vhost->partition_name, name, sizeof(vhost->partition_name)); + strscpy(vhost->partition_name, name, sizeof(vhost->partition_name)); num = of_get_property(rootdn, "ibm,partition-no", NULL); if (num) vhost->partition_number = *num;@@ -1498,13 +1498,15 @@ static void ibmvfc_set_login_info(struct ibmvfc_host *vhost) login_info->async.va = cpu_to_be64(vhost->async_crq.msg_token); login_info->async.len = cpu_to_be32(async_crq->size * sizeof(*async_crq->msgs.async)); - strncpy(login_info->partition_name, vhost->partition_name, IBMVFC_MAX_NAME); - strncpy(login_info->device_name, - dev_name(&vhost->host->shost_gendev), IBMVFC_MAX_NAME); + strscpy(login_info->partition_name, vhost->partition_name, + sizeof(login_info->partition_name)); + + strscpy(login_info->device_name, + dev_name(&vhost->host->shost_gendev), sizeof(login_info->device_name)); location = of_get_property(of_node, "ibm,loc-code", NULL); location = location ? location : dev_name(vhost->dev); - strncpy(login_info->drc_name, location, IBMVFC_MAX_NAME); + strscpy(login_info->drc_name, location, sizeof(login_info->drc_name)); } /**--- base-commit: ffc253263a1375a65fa6c9f62a893e9767fbebfa change-id: 20231030-strncpy-drivers-scsi-ibmvscsi-ibmvfc-c-ccfce3255d58 Best regards, -- Justin Stitt [off-list ref]
-- Kees Cook