[RFC PATCH v2 2/7] lib/cpio: Improve error handling

[Jonathan McDowell <noodles@fb.com>]

As preparation for making the cpio parsing routines more generally
available improve the error handling such that we pass back a suitable
errno rather than a string message, and correctly exit execution when
such an error is raised.

Signed-off-by: Jonathan McDowell <noodles@fb.com>
---
 include/linux/cpio.h |  1 -
 init/initramfs.c     | 10 ++++++--
 lib/cpio.c           | 56 +++++++++++++++++++++++++++-----------------
 3 files changed, 43 insertions(+), 24 deletions(-)

diff --git a/include/linux/cpio.h b/include/linux/cpio.h
index 2f9fd735331e..69a15fffa5c6 100644
--- a/include/linux/cpio.h
+++ b/include/linux/cpio.h
@@ -44,7 +44,6 @@ struct cpio_context {
 	unsigned long byte_count;
 	bool csum_present;
 	u32 io_csum;
-	char *errmsg;
 
 	char *collected;
 	long remains;
diff --git a/init/initramfs.c b/init/initramfs.c
index 00c101d04f4b..79c3a3f42cdb 100644
--- a/init/initramfs.c
+++ b/init/initramfs.c
@@ -62,10 +62,16 @@ static char * __init unpack_to_rootfs(char *buf, unsigned long len)
 		if (*buf == '0' && !(ctx.this_header & 3)) {
 			ctx.state = CPIO_START;
 			written = cpio_write_buffer(&ctx, buf, len);
+
+			if (written < 0) {
+				pr_err("Failed to process archive: %ld\n",
+				       written);
+				error("failed to process archive");
+				break;
+			}
+
 			buf += written;
 			len -= written;
-			if (ctx.errmsg)
-				message = ctx.errmsg;
 			continue;
 		}
 		if (!*buf) {
diff --git a/lib/cpio.c b/lib/cpio.c
index c71bebd4cc98..5d150939704f 100644
--- a/lib/cpio.c
+++ b/lib/cpio.c
@@ -221,12 +221,10 @@ static int __init do_header(struct cpio_context *ctx)
 		ctx->csum_present = false;
 	} else if (!memcmp(ctx->collected, "070702", 6)) {
 		ctx->csum_present = true;
+	} else if (memcmp(ctx->collected, "070707", 6) == 0) {
+		return -EPROTONOSUPPORT;
 	} else {
-		if (memcmp(ctx->collected, "070707", 6) == 0)
-			ctx->errmsg = "incorrect cpio method used: use -H newc option";
-		else
-			ctx->errmsg = "no cpio magic";
-		return 1;
+		return -EINVAL;
 	}
 	parse_header(ctx, ctx->collected);
 	ctx->next_header = ctx->this_header + N_ALIGN(ctx->name_len) + ctx->body_len;
@@ -266,7 +264,8 @@ static int __init do_reset(struct cpio_context *ctx)
 	while (ctx->byte_count && *ctx->victim == '\0')
 		eat(ctx, 1);
 	if (ctx->byte_count && (ctx->this_header & 3))
-		ctx->errmsg = "broken padding";
+		return -EFAULT;
+
 	return 1;
 }
 
@@ -344,23 +343,29 @@ static int __init do_name(struct cpio_context *ctx)
 
 static int __init do_copy(struct cpio_context *ctx)
 {
+	int ret;
+
 	if (ctx->byte_count >= ctx->body_len) {
-		if (xwrite(ctx, ctx->wfile, ctx->victim, ctx->body_len,
-			   &ctx->wfile_pos) != ctx->body_len)
-			ctx->errmsg = "write error";
+		ret = xwrite(ctx, ctx->wfile, ctx->victim, ctx->body_len,
+			     &ctx->wfile_pos);
+		if (ret != ctx->body_len)
+			return (ret < 0) ? ret : -EIO;
 
 		do_utime_path(&ctx->wfile->f_path, ctx->mtime);
 		fput(ctx->wfile);
 		if (ctx->csum_present && ctx->io_csum != ctx->hdr_csum)
-			ctx->errmsg = "bad data checksum";
+			return -EBADMSG;
+
 		eat(ctx, ctx->body_len);
 		ctx->state = CPIO_SKIPIT;
 		return 0;
 	}
 
-	if (xwrite(ctx, ctx->wfile, ctx->victim, ctx->byte_count,
-		   &ctx->wfile_pos) != ctx->byte_count)
-		ctx->errmsg = "write error";
+	ret = xwrite(ctx, ctx->wfile, ctx->victim, ctx->byte_count,
+		     &ctx->wfile_pos);
+	if (ret != ctx->byte_count)
+		return (ret < 0) ? ret : -EIO;
+
 	ctx->body_len -= ctx->byte_count;
 	eat(ctx, ctx->byte_count);
 	return 1;
@@ -392,12 +397,19 @@ static __initdata int (*actions[])(struct cpio_context *) = {
 long __init cpio_write_buffer(struct cpio_context *ctx, char *buf,
 			      unsigned long len)
 {
+	int ret;
+
 	ctx->byte_count = len;
 	ctx->victim = buf;
 
-	while (!actions[ctx->state](ctx))
-		;
-	return len - ctx->byte_count;
+	ret = 0;
+	while (ret == 0)
+		ret = actions[ctx->state](ctx);
+
+	if (ret < 0)
+		return ret;
+	else
+		return len - ctx->byte_count;
 }
 
 long __init cpio_process_buffer(struct cpio_context *ctx, void *bufv,
@@ -407,11 +419,13 @@ long __init cpio_process_buffer(struct cpio_context *ctx, void *bufv,
 	long written;
 	long left = len;
 
-	if (ctx->errmsg)
-		return -1;
+	while ((written = cpio_write_buffer(ctx, buf, left)) < left) {
+		char c;
+
+		if (written < 0)
+			return written;
 
-	while ((written = cpio_write_buffer(ctx, buf, left)) < left && !ctx->errmsg) {
-		char c = buf[written];
+		c = buf[written];
 
 		if (c == '0') {
 			buf += written;
@@ -422,7 +436,7 @@ long __init cpio_process_buffer(struct cpio_context *ctx, void *bufv,
 			left -= written;
 			ctx->state = CPIO_RESET;
 		} else {
-			ctx->errmsg = "junk within compressed archive";
+			return -EINVAL;
 		}
 	}
 
-- 
2.30.2