kernel: Restrict dmesg output to root.

In typical OpenWrt setups, there are no other users that have a shell spawned for them by default.

This can be overriden by the kernel.dmesg_output syssctl.

Signed-off-by: Rosen Penev <rosenp@gmail.com>

target/linux/generic/config-3.18

@@ -3284,7 +3284,7 @@ CONFIG_SCSI_PROC_FS=y
 # CONFIG_SECCOMP is not set
 # CONFIG_SECURITY is not set
 # CONFIG_SECURITYFS is not set
-# CONFIG_SECURITY_DMESG_RESTRICT is not set
+CONFIG_SECURITY_DMESG_RESTRICT=y
 # CONFIG_SEEQ8005 is not set
 CONFIG_SELECT_MEMORY_MODEL=y
 # CONFIG_SENSORS_ABITUGURU is not set

target/linux/generic/config-4.14

@@ -3998,7 +3998,7 @@ CONFIG_SCSI_PROC_FS=y
 CONFIG_SECTION_MISMATCH_WARN_ONLY=y
 # CONFIG_SECURITY is not set
 # CONFIG_SECURITYFS is not set
-# CONFIG_SECURITY_DMESG_RESTRICT is not set
+CONFIG_SECURITY_DMESG_RESTRICT=y
 CONFIG_SELECT_MEMORY_MODEL=y
 # CONFIG_SENSORS_ABITUGURU is not set
 # CONFIG_SENSORS_ABITUGURU3 is not set

target/linux/generic/config-4.4

@@ -3423,7 +3423,7 @@ CONFIG_SCSI_PROC_FS=y
 CONFIG_SECTION_MISMATCH_WARN_ONLY=y
 # CONFIG_SECURITY is not set
 # CONFIG_SECURITYFS is not set
-# CONFIG_SECURITY_DMESG_RESTRICT is not set
+CONFIG_SECURITY_DMESG_RESTRICT=y
 CONFIG_SELECT_MEMORY_MODEL=y
 # CONFIG_SENSORS_ABITUGURU is not set
 # CONFIG_SENSORS_ABITUGURU3 is not set

target/linux/generic/config-4.9

@@ -3766,7 +3766,7 @@ CONFIG_SCSI_PROC_FS=y
 CONFIG_SECTION_MISMATCH_WARN_ONLY=y
 # CONFIG_SECURITY is not set
 # CONFIG_SECURITYFS is not set
-# CONFIG_SECURITY_DMESG_RESTRICT is not set
+CONFIG_SECURITY_DMESG_RESTRICT=y
 CONFIG_SELECT_MEMORY_MODEL=y
 # CONFIG_SENSORS_ABITUGURU is not set
 # CONFIG_SENSORS_ABITUGURU3 is not set