| From 14d3625c3effc0070c7f802c15da622eac9fd169 Mon Sep 17 00:00:00 2001 |
| From: Sasha Levin <sashal@kernel.org> |
| Date: Fri, 16 Feb 2024 22:25:43 -0800 |
| Subject: x86: Increase brk randomness entropy for 64-bit systems |
| |
| From: Kees Cook <keescook@chromium.org> |
| |
| [ Upstream commit 44c76825d6eefee9eb7ce06c38e1a6632ac7eb7d ] |
| |
| In commit c1d171a00294 ("x86: randomize brk"), arch_randomize_brk() was |
| defined to use a 32MB range (13 bits of entropy), but was never increased |
| when moving to 64-bit. The default arch_randomize_brk() uses 32MB for |
| 32-bit tasks, and 1GB (18 bits of entropy) for 64-bit tasks. |
| |
| Update x86_64 to match the entropy used by arm64 and other 64-bit |
| architectures. |
| |
| Reported-by: y0un9n132@gmail.com |
| Signed-off-by: Kees Cook <keescook@chromium.org> |
| Signed-off-by: Thomas Gleixner <tglx@linutronix.de> |
| Acked-by: Jiri Kosina <jkosina@suse.com> |
| Closes: https://lore.kernel.org/linux-hardening/CA+2EKTVLvc8hDZc+2Yhwmus=dzOUG5E4gV7ayCbu0MPJTZzWkw@mail.gmail.com/ |
| Link: https://lore.kernel.org/r/20240217062545.1631668-1-keescook@chromium.org |
| Signed-off-by: Sasha Levin <sashal@kernel.org> |
| --- |
| arch/x86/kernel/process.c | 5 ++++- |
| 1 file changed, 4 insertions(+), 1 deletion(-) |
| |
| diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c |
| index b6f4e8399fca2..5351f293f770b 100644 |
| --- a/arch/x86/kernel/process.c |
| +++ b/arch/x86/kernel/process.c |
| @@ -1030,7 +1030,10 @@ unsigned long arch_align_stack(unsigned long sp) |
| |
| unsigned long arch_randomize_brk(struct mm_struct *mm) |
| { |
| - return randomize_page(mm->brk, 0x02000000); |
| + if (mmap_is_ia32()) |
| + return randomize_page(mm->brk, SZ_32M); |
| + |
| + return randomize_page(mm->brk, SZ_1G); |
| } |
| |
| /* |
| -- |
| 2.43.0 |
| |
