kernel: Activate CONFIG_SLAB_FREELIST_RANDOM

This activates CONFIG_SLAB_FREELIST_RANDOM.
This option make the free list less predictable. This makes it harder to
exploit heap based security vulnerabilities.

This adds a little bit more code to the kernel and a small additional
compute overhead.

This option is activated in Debian by default.

Signed-off-by: Hauke Mehrtens <[email protected]>

target/linux/generic/config-5.10

@@ -5464,7 +5464,7 @@ CONFIG_SIGNALFD=y
 # CONFIG_SLAB is not set
 CONFIG_SLABINFO=y
 CONFIG_SLAB_FREELIST_HARDENED=y
-# CONFIG_SLAB_FREELIST_RANDOM is not set
+CONFIG_SLAB_FREELIST_RANDOM=y
 CONFIG_SLAB_MERGE_DEFAULT=y
 # CONFIG_SLHC is not set
 # CONFIG_SLICOSS is not set

target/linux/generic/config-5.15

@@ -5754,7 +5754,7 @@ CONFIG_SIGNALFD=y
 # CONFIG_SLAB is not set
 CONFIG_SLABINFO=y
 CONFIG_SLAB_FREELIST_HARDENED=y
-# CONFIG_SLAB_FREELIST_RANDOM is not set
+CONFIG_SLAB_FREELIST_RANDOM=y
 CONFIG_SLAB_MERGE_DEFAULT=y
 # CONFIG_SLHC is not set
 # CONFIG_SLICOSS is not set