tree 743b949e550ec91fe2d7b366f5f4426f40a6d33e
parent ccd135cdd9c1839a42b3a07421023aade9dcce12
author Vlastimil Babka <vbabka@suse.cz> 1529681973 +0200
committer Greg Kroah-Hartman <gregkh@linuxfoundation.org> 1534347447 +0200

x86/speculation/l1tf: Protect PAE swap entries against L1TF

commit 0d0f6249058834ffe1ceaad0bb31464af66f6e7a upstream.

The PAE 3-level paging code currently doesn't mitigate L1TF by flipping the
offset bits, and uses the high PTE word, thus bits 32-36 for type, 37-63 for
offset. The lower word is zeroed, thus systems with less than 4GB memory are
safe. With 4GB to 128GB the swap type selects the memory locations vulnerable
to L1TF; with even more memory, also the swap offfset influences the address.
This might be a problem with 32bit PAE guests running on large 64bit hosts.

By continuing to keep the whole swap entry in either high or low 32bit word of
PTE we would limit the swap size too much. Thus this patch uses the whole PAE
PTE with the same layout as the 64bit version does. The macros just become a
bit tricky since they assume the arch-dependent swp_entry_t to be 32bit.

Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>