s390/kexec: fix return code handling

kexec_file_add_ipl_report ignores that ipl_report_finish may fail and
can return an error pointer instead of a valid pointer.
Fix this and simplify by returning NULL in case of an error and let
the only caller handle this case.

Fixes: 99feaa71 ("s390/kexec_file: Create ipl report and pass to next kernel")
Signed-off-by: NHeiko Carstens <hca@linux.ibm.com>

arch/s390/kernel/ipl.c

@@ -2156,7 +2156,7 @@ void *ipl_report_finish(struct ipl_report *report)
 
 	buf = vzalloc(report->size);
 	if (!buf)
-		return ERR_PTR(-ENOMEM);
+		goto out;
 	ptr = buf;
 
 	memcpy(ptr, report->ipib, report->ipib->hdr.len);
@@ -2195,6 +2195,7 @@ void *ipl_report_finish(struct ipl_report *report)
 	}
 
 	BUG_ON(ptr > buf + report->size);
+out:
 	return buf;
 }
 

arch/s390/kernel/machine_kexec_file.c

@@ -170,6 +170,7 @@ static int kexec_file_add_ipl_report(struct kimage *image,
 	struct kexec_buf buf;
 	unsigned long addr;
 	void *ptr, *end;
+	int ret;
 
 	buf.image = image;
 
@@ -199,7 +200,10 @@ static int kexec_file_add_ipl_report(struct kimage *image,
 		ptr += len;
 	}
 
+	ret = -ENOMEM;
 	buf.buffer = ipl_report_finish(data->report);
+	if (!buf.buffer)
+		goto out;
 	buf.bufsz = data->report->size;
 	buf.memsz = buf.bufsz;
 
@@ -209,7 +213,9 @@ static int kexec_file_add_ipl_report(struct kimage *image,
 		data->kernel_buf + offsetof(struct lowcore, ipl_parmblock_ptr);
 	*lc_ipl_parmblock_ptr = (__u32)buf.mem;
 
-	return kexec_add_buffer(&buf);
+	ret = kexec_add_buffer(&buf);
+out:
+	return ret;
 }
 
 void *kexec_file_add_components(struct kimage *image,