On 11/30/23 13:25, Kees Cook wrote: > 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? Sorry, for a delayed response. I've just taken over the maintainer role as it had been left unaccounted for sometime. These are meant to be handled as C strings and nul termination is expected. -Tyrel > >> >> 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 >
