[PATCH 3.12 072/142] MIPS: OCTEON: make get_system_type() thread-safe

From: Jiri Slaby
Date: Fri Sep 26 2014 - 06:14:38 EST


From: Aaro Koskinen <aaro.koskinen@xxxxxxx>

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@xxxxxxx>
Reviewed-by: Markos Chandras <markos.chandras@xxxxxxxxxx>
Patchwork: http://patchwork.linux-mips.org/patch/7437/
Signed-off-by: James Hogan <james.hogan@xxxxxxxxxx>
Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
---
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

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/