[ 045/221] pstore/ram: Fix undefined usage of rounddown_pow_of_two(0)

[Greg Kroah-Hartman]

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

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

From: Maxime Bizon <mbizon@xxxxxxxxxx>

commit b042e47491ba5f487601b5141a3f1d8582304170 upstream.

record_size / console_size / ftrace_size can be 0 (this is how you disable
the feature), but rounddown_pow_of_two(0) is undefined. As suggested by
Kees Cook, use !is_power_of_2() as a condition to call
rounddown_pow_of_two and avoid its undefined behavior on the value 0. This
issue has been present since commit 1894a253 (ramoops: Move to
fs/pstore/ram.c).

Signed-off-by: Maxime Bizon <mbizon@xxxxxxxxxx>
Signed-off-by: Florian Fainelli <ffainelli@xxxxxxxxxx>
Acked-by: Kees Cook <keescook@xxxxxxxxxxxx>
Signed-off-by: Anton Vorontsov <anton.vorontsov@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 fs/pstore/ram.c |   12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

--- a/fs/pstore/ram.c
+++ b/fs/pstore/ram.c
@@ -374,10 +374,14 @@ static int __devinit ramoops_probe(struc
 		goto fail_out;
 	}
 
-	pdata->mem_size = rounddown_pow_of_two(pdata->mem_size);
-	pdata->record_size = rounddown_pow_of_two(pdata->record_size);
-	pdata->console_size = rounddown_pow_of_two(pdata->console_size);
-	pdata->ftrace_size = rounddown_pow_of_two(pdata->ftrace_size);
+	if (!is_power_of_2(pdata->mem_size))
+		pdata->mem_size = rounddown_pow_of_two(pdata->mem_size);
+	if (!is_power_of_2(pdata->record_size))
+		pdata->record_size = rounddown_pow_of_two(pdata->record_size);
+	if (!is_power_of_2(pdata->console_size))
+		pdata->console_size = rounddown_pow_of_two(pdata->console_size);
+	if (!is_power_of_2(pdata->ftrace_size))
+		pdata->ftrace_size = rounddown_pow_of_two(pdata->ftrace_size);
 
 	cxt->dump_read_cnt = 0;
 	cxt->size = pdata->mem_size;


--
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/