linux-hardening - [PATCH 0/2] Adjust brk randomness

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Message-Id: <20240217062035.work.493-kees@kernel.org>
Date: Fri, 16 Feb 2024 22:25:42 -0800
From: Kees Cook <keescook@...omium.org>
To: Jiri Kosina <jikos@...nel.org>
Cc: Kees Cook <keescook@...omium.org>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Qi Zheng <zhengqi.arch@...edance.com>,
	Alexandre Ghiti <alexghiti@...osinc.com>,
	Al Viro <viro@...iv.linux.org.uk>,
	Christian Brauner <brauner@...nel.org>,
	Jan Kara <jack@...e.cz>,
	Eric Biederman <ebiederm@...ssion.com>,
	Christophe Leroy <christophe.leroy@...roup.eu>,
	Josh Poimboeuf <jpoimboe@...nel.org>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Rick Edgecombe <rick.p.edgecombe@...el.com>,
	Brian Gerst <brgerst@...il.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Tony Battersby <tonyb@...ernetics.com>,
	linux-kernel@...r.kernel.org,
	y0un9n132@...il.com,
	x86@...nel.org,
	linux-fsdevel@...r.kernel.org,
	linux-mm@...ck.org,
	linux-hardening@...r.kernel.org
Subject: [PATCH 0/2] Adjust brk randomness

Hi,

It was recently pointed out[1] that x86_64 brk entropy was not great,
and that on all architectures the brk can (when the random offset is 0)
be immediately adjacent to .bss, leaving no gap that could stop linear
overflows from the .bss. Address both issues.

-Kees

Link: https://lore.kernel.org/linux-hardening/CA+2EKTVLvc8hDZc+2Yhwmus=dzOUG5E4gV7ayCbu0MPJTZzWkw@mail.gmail.com [1]

Kees Cook (2):
  x86: Increase brk randomness entropy on x86_64
  binfmt_elf: Leave a gap between .bss and brk

 arch/x86/kernel/process.c | 5 ++++-
 fs/binfmt_elf.c           | 3 +++
 2 files changed, 7 insertions(+), 1 deletion(-)

-- 
2.34.1