5.4-stable review patch. If anyone has any objections, please let me know.
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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=dzOUG5E4gV7... 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 b8de27bb6e09c..c402b079b74e8 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -793,7 +793,10 @@ 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); }
/*