| Message ID | 20240217062545.1631668-1-keescook@chromium.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Adjust brk randomness | expand |
On Fri, 16 Feb 2024, Kees Cook wrote: > 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 > Closes: https://lore.kernel.org/linux-hardening/CA+2EKTVLvc8hDZc+2Yhwmus=dzOUG5E4gV7ayCbu0MPJTZzWkw@mail.gmail.com/ > Signed-off-by: Kees Cook <keescook@chromium.org> Wow, this is a pretty aged code indeed. Acked-by: Jiri Kosina <jkosina@suse.com> Thanks,
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); } /*
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 Closes: https://lore.kernel.org/linux-hardening/CA+2EKTVLvc8hDZc+2Yhwmus=dzOUG5E4gV7ayCbu0MPJTZzWkw@mail.gmail.com/ Signed-off-by: Kees Cook <keescook@chromium.org> --- Cc: Jiri Kosina <jikos@kernel.org> Cc: Geert Uytterhoeven <geert@linux-m68k.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Qi Zheng <zhengqi.arch@bytedance.com> Cc: Alexandre Ghiti <alexghiti@rivosinc.com> Cc: x86@kernel.org --- arch/x86/kernel/process.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)