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: [email protected] Closes: https://lore.kernel.org/linux-hardening/CA+2EKTVLvc8hDZc+2Yhwmus=dzoug5e4gv7aycbu0mpjtzz...@mail.gmail.com/ Signed-off-by: Kees Cook <[email protected]> --- Cc: Jiri Kosina <[email protected]> Cc: Geert Uytterhoeven <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: Ingo Molnar <[email protected]> Cc: Borislav Petkov <[email protected]> Cc: Dave Hansen <[email protected]> Cc: "H. Peter Anvin" <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Qi Zheng <[email protected]> Cc: Alexandre Ghiti <[email protected]> Cc: [email protected] --- 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 ab49ade31b0d..45a9d496fe2a 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); } /* -- 2.34.1
