Re: [PATCH 13/20] scsi: zfcp: Manual replacement of the deprecated strlcpy() with return values

Benjamin Block
2021-02-22T16:10:58Z

On Mon, Feb 22, 2021 at 04:12:24PM +0100, Romain Perier wrote:
> The strlcpy() reads the entire source buffer first, it is dangerous if
> the source buffer lenght is unbounded or possibility non NULL-terminated.
> It can lead to linear read overflows, crashes, etc...
>
> As recommended in the deprecated interfaces [1], it should be replaced
> by strscpy.
>
> This commit replaces all calls to strlcpy that handle the return values
> by the corresponding strscpy calls with new handling of the return
> values (as it is quite different between the two functions).
>
> [1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy
>
> Signed-off-by: Romain Perier <romain.perier@gmail.com>
> ---
> drivers/s390/scsi/zfcp_fc.c | 8 +++++---
> 1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/s390/scsi/zfcp_fc.c b/drivers/s390/scsi/zfcp_fc.c
> index d24cafe02708..8a65241011b9 100644
> --- a/drivers/s390/scsi/zfcp_fc.c
> +++ b/drivers/s390/scsi/zfcp_fc.c
> @@ -877,14 +877,16 @@ static void zfcp_fc_rspn(struct zfcp_adapter *adapter,
> struct zfcp_fsf_ct_els *ct_els = &fc_req->ct_els;
> struct zfcp_fc_rspn_req *rspn_req = &fc_req->u.rspn.req;
> struct fc_ct_hdr *rspn_rsp = &fc_req->u.rspn.rsp;
> - int ret, len;
> + int ret;
> + ssize_t len;
>
> zfcp_fc_ct_ns_init(&rspn_req->ct_hdr, FC_NS_RSPN_ID,
> FC_SYMBOLIC_NAME_SIZE);
> hton24(rspn_req->rspn.fr_fid.fp_fid, fc_host_port_id(shost));
> - len = strlcpy(rspn_req->rspn.fr_name, fc_host_symbolic_name(shost),
> + len = strscpy(rspn_req->rspn.fr_name, fc_host_symbolic_name(shost),
> FC_SYMBOLIC_NAME_SIZE);
> - rspn_req->rspn.fr_name_len = len;
> + if (len != -E2BIG)
> + rspn_req->rspn.fr_name_len = len;

That is a bug. Leaving `rspn.fr_name_len` uninitialized defeats the
purpose of sending a RSPN.

How about:
if (len == -E2BIG)
rspn_req->rspn.fr_name_len = FC_SYMBOLIC_NAME_SIZE - 1;
else
rspn_req->rspn.fr_name_len = len;

>
> sg_init_one(&fc_req->sg_req, rspn_req, sizeof(*rspn_req));
> sg_init_one(&fc_req->sg_rsp, rspn_rsp, sizeof(*rspn_rsp));
>

--
Best Regards, Benjamin Block / Linux on IBM Z Kernel Development / IBM Systems
IBM Deutschland Research & Development GmbH / https://www.ibm.com/privacy
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