edac, mce: Filter out invalid values

Print the CPU associated with the error only when the field is valid.

Cc: <stable@kernel.org> # .32.x .33.x
Signed-off-by: Borislav Petkov <borislav.petkov@amd.com>

drivers/edac/edac_mce_amd.c

@@ -316,7 +316,12 @@ void amd_decode_nb_mce(int node_id, struct err_regs *regs, int handle_errors)
 		if (regs->nbsh & K8_NBSH_ERR_CPU_VAL)
 			pr_cont(", core: %u\n", (u8)(regs->nbsh & 0xf));
 	} else {
-		pr_cont(", core: %d\n", fls((regs->nbsh & 0xf) - 1));
+		u8 assoc_cpus = regs->nbsh & 0xf;
+
+		if (assoc_cpus > 0)
+			pr_cont(", core: %d", fls(assoc_cpus) - 1);
+
+		pr_cont("\n");
 	}
 
 	pr_emerg("%s.\n", EXT_ERR_MSG(xec));