From: Matthew Garrett Date: Fri, 9 Mar 2012 08:39:37 -0500 Subject: [06/18] acpi: Limit access to custom_method if securelevel is set Origin: https://github.com/mjg59/linux/commit/3cdc48db6b6d1b3cc1412d428389889f74cafe83 custom_method effectively allows arbitrary access to system memory, making it possible for an attacker to modify the kernel at runtime. Prevent this if securelevel has been set. Signed-off-by: Matthew Garrett --- drivers/acpi/custom_method.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/drivers/acpi/custom_method.c b/drivers/acpi/custom_method.c index c68e72414a67..359f45d54543 100644 --- a/drivers/acpi/custom_method.c +++ b/drivers/acpi/custom_method.c @@ -8,6 +8,7 @@ #include #include #include +#include #include "internal.h" @@ -29,6 +30,9 @@ static ssize_t cm_write(struct file *file, const char __user * user_buf, struct acpi_table_header table; acpi_status status; + if (get_securelevel() > 0) + return -EPERM; + if (!(*ppos)) { /* parse the table header to get the table length */ if (count <= sizeof(struct acpi_table_header))