On Mon, Oct 30, 2023 at 09:43:20PM +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 don't need the NUL-padding behavior that strncpy() provides as vscsi > is NUL-allocated in ibmvscsis_probe() which proceeds to call > ibmvscsis_adapter_info(): > | vscsi = kzalloc(sizeof(*vscsi), GFP_KERNEL); > > ibmvscsis_probe() -> ibmvscsis_handle_crq() -> ibmvscsis_parse_command() > -> ibmvscsis_mad() -> ibmvscsis_process_mad() -> ibmvscsis_adapter_info() > > Following the same idea, `partition_name` is defiend as: > | static char partition_name[PARTITION_NAMELEN] = "UNKNOWN"; > > ... which is NUL-padded already, meaning strscpy() is the best option. > > 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. My only worry here is that I don't see if %NUL termination is _required_ for these variables. (i.e. do we run the risk of truncating these by 1 byte if they're right at the limit?) Are they __nonstring? I *think* they're %NUL terminated since they follow the same sizing as the global "partition_name", but I'm not sure. Can any of the SCSI authors comment on this? > > However, for cap->name let's use strscpy_pad as cap is allocated via > dma_alloc_coherent(): > | cap = dma_alloc_coherent(&vscsi->dma_dev->dev, olen, &token, > | GFP_ATOMIC); This is also true for the "info" allocation (it comes out of DMA). > > 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/scsi/ibmvscsi_tgt/ibmvscsi_tgt.c | 14 +++++++------- > 1 file changed, 7 insertions(+), 7 deletions(-) > > diff --git a/drivers/scsi/ibmvscsi_tgt/ibmvscsi_tgt.c b/drivers/scsi/ibmvscsi_tgt/ibmvscsi_tgt.c > index 385f812b8793..cd223ef696e5 100644 > --- a/drivers/scsi/ibmvscsi_tgt/ibmvscsi_tgt.c > +++ b/drivers/scsi/ibmvscsi_tgt/ibmvscsi_tgt.c > @@ -1551,17 +1551,17 @@ static long ibmvscsis_adapter_info(struct scsi_info *vscsi, > if (vscsi->client_data.partition_number == 0) > vscsi->client_data.partition_number = > be32_to_cpu(info->partition_number); > - strncpy(vscsi->client_data.srp_version, info->srp_version, > + strscpy(vscsi->client_data.srp_version, info->srp_version, > sizeof(vscsi->client_data.srp_version)); > - strncpy(vscsi->client_data.partition_name, info->partition_name, > + strscpy(vscsi->client_data.partition_name, info->partition_name, > sizeof(vscsi->client_data.partition_name)); > vscsi->client_data.mad_version = be32_to_cpu(info->mad_version); > vscsi->client_data.os_type = be32_to_cpu(info->os_type); > > /* Copy our info */ > - strncpy(info->srp_version, SRP_VERSION, > + strscpy(info->srp_version, SRP_VERSION, > sizeof(info->srp_version)); > - strncpy(info->partition_name, vscsi->dds.partition_name, > + strscpy(info->partition_name, vscsi->dds.partition_name, > sizeof(info->partition_name)); Since "info" is from DMA, let's use the _pad variant here just to be safe. > info->partition_number = cpu_to_be32(vscsi->dds.partition_num); > info->mad_version = cpu_to_be32(MAD_VERSION_1); > @@ -1645,8 +1645,8 @@ static int ibmvscsis_cap_mad(struct scsi_info *vscsi, struct iu_entry *iue) > be64_to_cpu(mad->buffer), > vscsi->dds.window[LOCAL].liobn, token); > if (rc == H_SUCCESS) { > - strncpy(cap->name, dev_name(&vscsi->dma_dev->dev), > - SRP_MAX_LOC_LEN); > + strscpy_pad(cap->name, dev_name(&vscsi->dma_dev->dev), > + sizeof(cap->name)); And this is a safe conversion to sizeof(): struct capabilities { ... char name[SRP_MAX_LOC_LEN]; If we can convince ourselves that non of these are __nonstring types, then I think with the "info" change above, this should be good. -Kees -- Kees Cook
