When implementing support for retrieval of local diagnostic data from the FCP channel, the wrong data format was assumed for the temperature of the local SFP+ connector. The Fibre Channel Link Services (FC-LS-3) specification is not clear on the format of the stored integer, and only after consulting the SNIA specification SFF-8472 did we realize it is stored as two's complement. Thus, the used data and display format is wrong, and highly misleading for users when the temperature should drop below 0°C (however unlikely that may be).

To fix this, change the data format in `struct fsf_qtcb_bottom_port` from unsigned to signed, and change the printf format string used to generate `zfcp_sysfs_adapter_diag_sfp_temperature_show()` from `%hu` to `%hd`.

Fixes: a10a61e807b0 ("scsi: zfcp: support retrieval of SFP Data via Exchange Port Data") Fixes: 6028f7c4cd87 ("scsi: zfcp: introduce sysfs interface for diagnostics of local SFP transceiver") Cc: stable@vger.kernel.org # 5.5+ Reviewed-by: Jens Remus jremus@linux.ibm.com Reviewed-by: Fedor Loshakov loshakov@linux.ibm.com Reviewed-by: Steffen Maier maier@linux.ibm.com Signed-off-by: Benjamin Block bblock@linux.ibm.com ---

Hello James, Martin,

please consider this patch to be included in scsi-fixes, I also tagged it for stable. It fixes a bug I found with the exposed hardware diagnostics we introduced with 5.5.

Tests have been done by injecting negative temperatures in the used data structures, in the same format specified in SNIA's SFF-8472 (Table 9-2).

crash vmlinux /proc/kcore p ((struct zfcp_adapter *)((struct ccw_device *)0x00000001be250800)->dev.driver_data)->diagnostics->port_data.data.temperature $8 = 0xffff crash> ^Z [1]+ Stopped crash vmlinux /proc/kcore ~ # cat /sys/bus/ccw/drivers/zfcp/0.0.1900/diagnostics/temperature -1

crash vmlinux /proc/kcore p ((struct zfcp_adapter *)((struct ccw_device *)0x00000001be250800)->dev.driver_data)->diagnostics->port_data.data.temperature $9 = 0xff00 crash> ^Z [1]+ Stopped crash vmlinux /proc/kcore ~ # cat /sys/bus/ccw/drivers/zfcp/0.0.1900/diagnostics/temperature -256

Reviews and comments are welcome :-).

drivers/s390/scsi/zfcp_fsf.h | 2 +- drivers/s390/scsi/zfcp_sysfs.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/s390/scsi/zfcp_fsf.h b/drivers/s390/scsi/zfcp_fsf.h index 2b1e4da1944f..4bfb79f20588 100644 --- a/drivers/s390/scsi/zfcp_fsf.h +++ b/drivers/s390/scsi/zfcp_fsf.h @@ -410,7 +410,7 @@ struct fsf_qtcb_bottom_port { u8 cb_util; u8 a_util; u8 res2; - u16 temperature; + s16 temperature; u16 vcc; u16 tx_bias; u16 tx_power; diff --git a/drivers/s390/scsi/zfcp_sysfs.c b/drivers/s390/scsi/zfcp_sysfs.c index 494b9fe9cc94..a711a0d15100 100644 --- a/drivers/s390/scsi/zfcp_sysfs.c +++ b/drivers/s390/scsi/zfcp_sysfs.c @@ -800,7 +800,7 @@ static ZFCP_DEV_ATTR(adapter_diag, b2b_credit, 0400, static ZFCP_DEV_ATTR(adapter_diag_sfp, _name, 0400, \ zfcp_sysfs_adapter_diag_sfp_##_name##_show, NULL)

-ZFCP_DEFINE_DIAG_SFP_ATTR(temperature, temperature, 5, "%hu"); +ZFCP_DEFINE_DIAG_SFP_ATTR(temperature, temperature, 6, "%hd"); ZFCP_DEFINE_DIAG_SFP_ATTR(vcc, vcc, 5, "%hu"); ZFCP_DEFINE_DIAG_SFP_ATTR(tx_bias, tx_bias, 5, "%hu"); ZFCP_DEFINE_DIAG_SFP_ATTR(tx_power, tx_power, 5, "%hu");