linux-kernel - [PATCH 4.4 19/26] of: Add check to of_scan_flat_dt() before accessing initial_boot

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Message-Id: <20170627124531.558809383@linuxfoundation.org>
Date:   Tue, 27 Jun 2017 14:49:56 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Tobias Wolf <dev-NTEO@...ace.de>,
        Sergei Shtylyov <sergei.shtylyov@...entembedded.com>,
        linux-mips@...ux-mips.org, Ralf Baechle <ralf@...ux-mips.org>,
        Amit Pundir <amit.pundir@...aro.org>
Subject: [PATCH 4.4 19/26] of: Add check to of_scan_flat_dt() before accessing initial_boot_params

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Tobias Wolf <dev-NTEO@...ace.de>

commit 3ec754410cb3e931a6c4920b1a150f21a94a2bf4 upstream.

An empty __dtb_start to __dtb_end section might result in
initial_boot_params being null for arch/mips/ralink. This showed that the
boot process hangs indefinitely in of_scan_flat_dt().

Signed-off-by: Tobias Wolf <dev-NTEO@...ace.de>
Cc: Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
Cc: linux-mips@...ux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/14605/
Signed-off-by: Ralf Baechle <ralf@...ux-mips.org>
Signed-off-by: Amit Pundir <amit.pundir@...aro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/of/fdt.c |    9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

--- a/drivers/of/fdt.c
+++ b/drivers/of/fdt.c
@@ -632,9 +632,12 @@ int __init of_scan_flat_dt(int (*it)(uns
 	const char *pathp;
 	int offset, rc = 0, depth = -1;
 
-        for (offset = fdt_next_node(blob, -1, &depth);
-             offset >= 0 && depth >= 0 && !rc;
-             offset = fdt_next_node(blob, offset, &depth)) {
+	if (!blob)
+		return 0;
+
+	for (offset = fdt_next_node(blob, -1, &depth);
+	     offset >= 0 && depth >= 0 && !rc;
+	     offset = fdt_next_node(blob, offset, &depth)) {
 
 		pathp = fdt_get_name(blob, offset, NULL);
 		if (*pathp == '/')