From 71a5849aedaa9ea028fc51ee74576cad61954743 Mon Sep 17 00:00:00 2001 From: Sami Tolvanen Date: Fri, 29 Sep 2023 21:11:57 +0000 Subject: [PATCH 1/2] mm: Change mmap_rnd_bits_max to __ro_after_init Allow mmap_rnd_bits_max to be updated on architectures that determine virtual address space size at runtime instead of relying on Kconfig options by changing it from const to __ro_after_init. Signed-off-by: Sami Tolvanen Reviewed-by: Kees Cook Reviewed-by: Palmer Dabbelt Acked-by: Palmer Dabbelt Link: https://lore.kernel.org/r/20230929211155.3910949-5-samitolvanen@google.com Signed-off-by: Palmer Dabbelt --- include/linux/mm.h | 2 +- mm/mmap.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index f5a97dec5169..2488c0c5a288 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -86,7 +86,7 @@ extern int sysctl_legacy_va_layout; #ifdef CONFIG_HAVE_ARCH_MMAP_RND_BITS extern const int mmap_rnd_bits_min; -extern const int mmap_rnd_bits_max; +extern int mmap_rnd_bits_max __ro_after_init; extern int mmap_rnd_bits __read_mostly; #endif #ifdef CONFIG_HAVE_ARCH_MMAP_RND_COMPAT_BITS diff --git a/mm/mmap.c b/mm/mmap.c index b78e83d351d2..8f47011de22e 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -64,7 +64,7 @@ #ifdef CONFIG_HAVE_ARCH_MMAP_RND_BITS const int mmap_rnd_bits_min = CONFIG_ARCH_MMAP_RND_BITS_MIN; -const int mmap_rnd_bits_max = CONFIG_ARCH_MMAP_RND_BITS_MAX; +int mmap_rnd_bits_max __ro_after_init = CONFIG_ARCH_MMAP_RND_BITS_MAX; int mmap_rnd_bits __read_mostly = CONFIG_ARCH_MMAP_RND_BITS; #endif #ifdef CONFIG_HAVE_ARCH_MMAP_RND_COMPAT_BITS From 7df1ff5a5cd615815bc6fb4a3a981e9746935e59 Mon Sep 17 00:00:00 2001 From: Sami Tolvanen Date: Fri, 29 Sep 2023 21:11:58 +0000 Subject: [PATCH 2/2] riscv: mm: Update mmap_rnd_bits_max ARCH_MMAP_RND_BITS_MAX is based on Sv39, which leaves a few potential bits of mmap randomness on the table if we end up enabling 4/5-level paging. Update mmap_rnd_bits_max to take the final address space size into account. This increases mmap_rnd_bits_max from 24 to 33 with Sv48/57. Signed-off-by: Sami Tolvanen Reviewed-by: Kees Cook Reviewed-by: Palmer Dabbelt Acked-by: Palmer Dabbelt Link: https://lore.kernel.org/r/20230929211155.3910949-6-samitolvanen@google.com Signed-off-by: Palmer Dabbelt --- arch/riscv/mm/init.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c index 32cad6a65ccd..c55915554836 100644 --- a/arch/riscv/mm/init.c +++ b/arch/riscv/mm/init.c @@ -767,6 +767,11 @@ static int __init print_no5lvl(char *p) } early_param("no5lvl", print_no5lvl); +static void __init set_mmap_rnd_bits_max(void) +{ + mmap_rnd_bits_max = MMAP_VA_BITS - PAGE_SHIFT - 3; +} + /* * There is a simple way to determine if 4-level is supported by the * underlying hardware: establish 1:1 mapping in 4-level page table mode @@ -1081,6 +1086,7 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa) #if defined(CONFIG_64BIT) && !defined(CONFIG_XIP_KERNEL) set_satp_mode(dtb_pa); + set_mmap_rnd_bits_max(); #endif /*