[ndctl PATCH] papr: Check for command type in papr_xlat_firmware_status()

[Vaibhav Jain <vaibhav@linux.ibm.com>]

We recently discovered intermittent failures while reading label-area
of PAPR-NVDimms and the command 'read-labels' would in such a case
generated empty output like below:

$ sudo ndctl read-labels -j nmem0
[
]
read 0 nmem

Upon investigation we found that this was caused by a spurious error
code returned from ndctl_cmd_submit_xlat() when its called from
ndctl_dimm_read_label_extent() while trying to read the label-area
contents of the NVDIMM.

Digging further it was relieved that ndctl_cmd_submit_xlat() would
always call papr_xlat_firmware_status() via pointer
'papr_dimm_ops->xlat_firmware_status' to retrieve translated firmware
status for all ndctl_cmds even though they arent really PAPR PDSM
commands.

In this case ndctl_cmd->type == ND_CMD_GET_CONFIG_DATA and was
represented by type 'struct nd_cmd_get_config_data_hdr' and
papr_xlat_firmware_status() incorrectly assumed it to be of type
'struct nd_pkg_pdsm' and wrongly dereferenced it returning an invalid
value.

A proper fix for this would probably need introducing a new ndctl_cmd
callback like 'ndctl_cmd.get_xlat_firmware_status' similar to one
introduced in [1]. However such a change could be disruptive, hence
the patch introduces a small workaround in papr_xlat_firmware_status()
that checks if the 'struct ndctl_cmd *' provided if of correct type
CMD_CALL and if not then it ignores it and return '0'

References:
[1]: commit fa754dd8acdb ("ndctl/dimm: Rework dimm command status
reporting")

Fixes: 151d2876c49e ("papr: Add scaffolding to issue and handle PDSM requests")
Reported-by: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
Signed-off-by: Vaibhav Jain <vaibhav@linux.ibm.com>
---
 ndctl/lib/papr.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/ndctl/lib/papr.c b/ndctl/lib/papr.c
index d9ce253369b3..63561f8f9797 100644
--- a/ndctl/lib/papr.c
+++ b/ndctl/lib/papr.c
@@ -56,9 +56,7 @@ static u32 papr_get_firmware_status(struct ndctl_cmd *cmd)
 
 static int papr_xlat_firmware_status(struct ndctl_cmd *cmd)
 {
-	const struct nd_pkg_pdsm *pcmd = to_pdsm(cmd);
-
-	return pcmd->cmd_status;
+	return (cmd->type == ND_CMD_CALL) ? to_pdsm(cmd)->cmd_status : 0;
 }
 
 /* Verify if the given command is supported and valid */
-- 
2.26.2
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