diff options
| author | Lee Jones <lee@kernel.org> | 2023-06-14 17:38:54 +0100 |
|---|---|---|
| committer | Dave Hansen <dave.hansen@linux.intel.com> | 2023-06-16 11:46:42 -0700 |
| commit | d082d48737c75d2b3cc1f972b8c8674c25131534 (patch) | |
| tree | 6eab63089abd0c8fb2a18710102d851ca099b60c /arch | |
| parent | a37f2699c36a7f6606ba3300f243227856c5ad6b (diff) | |
x86/mm: Avoid using set_pgd() outside of real PGD pages
KPTI keeps around two PGDs: one for userspace and another for the
kernel. Among other things, set_pgd() contains infrastructure to
ensure that updates to the kernel PGD are reflected in the user PGD
as well.
One side-effect of this is that set_pgd() expects to be passed whole
pages. Unfortunately, init_trampoline_kaslr() passes in a single entry:
'trampoline_pgd_entry'.
When KPTI is on, set_pgd() will update 'trampoline_pgd_entry' (an
8-Byte globally stored [.bss] variable) and will then proceed to
replicate that value into the non-existent neighboring user page
(located +4k away), leading to the corruption of other global [.bss]
stored variables.
Fix it by directly assigning 'trampoline_pgd_entry' and avoiding
set_pgd().
[ dhansen: tweak subject and changelog ]
Fixes: 0925dda5962e ("x86/mm/KASLR: Use only one PUD entry for real mode trampoline")
Suggested-by: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: Lee Jones <lee@kernel.org>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/all/20230614163859.924309-1-lee@kernel.org/g
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/x86/mm/kaslr.c | 8 |
1 files changed, 4 insertions, 4 deletions
diff --git a/arch/x86/mm/kaslr.c b/arch/x86/mm/kaslr.c index 557f0fe25dff..37db264866b6 100644 --- a/arch/x86/mm/kaslr.c +++ b/arch/x86/mm/kaslr.c @@ -172,10 +172,10 @@ void __meminit init_trampoline_kaslr(void) set_p4d(p4d_tramp, __p4d(_KERNPG_TABLE | __pa(pud_page_tramp))); - set_pgd(&trampoline_pgd_entry, - __pgd(_KERNPG_TABLE | __pa(p4d_page_tramp))); + trampoline_pgd_entry = + __pgd(_KERNPG_TABLE | __pa(p4d_page_tramp)); } else { - set_pgd(&trampoline_pgd_entry, - __pgd(_KERNPG_TABLE | __pa(pud_page_tramp))); + trampoline_pgd_entry = + __pgd(_KERNPG_TABLE | __pa(pud_page_tramp)); } } |