EDAC/versal: Check user-supplied data before injecting an error

The function inject_data_ue_store() lacks a NULL check for the user
passed values. To prevent below kernel crash include a NULL check.

Call trace:

kstrtoull
kstrtou8
inject_data_ue_store
full_proxy_write
vfs_write
ksys_write
__arm64_sys_write
invoke_syscall
el0_svc_common.constprop.0
do_el0_svc
el0_svc
el0t_64_sync_handler
el0t_64_sync

Fixes: 83bf24051a60 ("EDAC/versal: Make the bit position of injected errors configurable")
Signed-off-by: Shubhrajyoti Datta <[e-mail]>
Signed-off-by: Borislav Petkov (AMD) <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

drivers/edac/versal_edac.c

···
 	for (i = 0; i < NUM_UE_BITPOS; i++)
 		token[i] = strsep(&pbuf, ",");
 
+	if (!token[0] || !token[1])
+		return -EFAULT;
+
 	ret = kstrtou8(token[0], 0, &ue0);
 	if (ret)
 		return ret;