linux-kernel - [PATCH 3.12 072/142] MIPS: OCTEON: make get_system

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Message-Id: <1e1c3a21579aa9ea0429b69165caef77cca27f7e.1411724724.git.jslaby@suse.cz>
Date:	Fri, 26 Sep 2014 11:44:43 +0200
From:	Jiri Slaby <jslaby@...e.cz>
To:	stable@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org,
	Aaro Koskinen <aaro.koskinen@....com>,
	James Hogan <james.hogan@...tec.com>,
	Jiri Slaby <jslaby@...e.cz>
Subject: [PATCH 3.12 072/142] MIPS: OCTEON: make get_system_type() thread-safe

From: Aaro Koskinen <aaro.koskinen@....com>

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

===============

commit 608308682addfdc7b8e2aee88f0e028331d88e4d upstream.

get_system_type() is not thread-safe on OCTEON. It uses static data,
also more dangerous issue is that it's calling cvmx_fuse_read_byte()
every time without any synchronization. Currently it's possible to get
processes stuck looping forever in kernel simply by launching multiple
readers of /proc/cpuinfo:

	(while true; do cat /proc/cpuinfo > /dev/null; done) &
	(while true; do cat /proc/cpuinfo > /dev/null; done) &
	...

Fix by initializing the system type string only once during the early
boot.

Signed-off-by: Aaro Koskinen <aaro.koskinen@....com>
Reviewed-by: Markos Chandras <markos.chandras@...tec.com>
Patchwork: http://patchwork.linux-mips.org/patch/7437/
Signed-off-by: James Hogan <james.hogan@...tec.com>
Signed-off-by: Jiri Slaby <jslaby@...e.cz>
---
 arch/mips/cavium-octeon/setup.c | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/arch/mips/cavium-octeon/setup.c b/arch/mips/cavium-octeon/setup.c
index b212ae12e5ac..8a0079981cc8 100644
--- a/arch/mips/cavium-octeon/setup.c
+++ b/arch/mips/cavium-octeon/setup.c
@@ -458,6 +458,18 @@ static void octeon_halt(void)
 	octeon_kill_core(NULL);
 }
 
+static char __read_mostly octeon_system_type[80];
+
+static int __init init_octeon_system_type(void)
+{
+	snprintf(octeon_system_type, sizeof(octeon_system_type), "%s (%s)",
+		cvmx_board_type_to_string(octeon_bootinfo->board_type),
+		octeon_model_get_string(read_c0_prid()));
+
+	return 0;
+}
+early_initcall(init_octeon_system_type);
+
 /**
  * Return a string representing the system type
  *
@@ -465,11 +477,7 @@ static void octeon_halt(void)
  */
 const char *octeon_board_type_string(void)
 {
-	static char name[80];
-	sprintf(name, "%s (%s)",
-		cvmx_board_type_to_string(octeon_bootinfo->board_type),
-		octeon_model_get_string(read_c0_prid()));
-	return name;
+	return octeon_system_type;
 }
 
 const char *get_system_type(void)
-- 
2.1.0

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