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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id p17sm5917461pfn.62.2021.03.09.13.43.10 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 09 Mar 2021 13:43:11 -0800 (PST) From: Kees Cook To: Thomas Gleixner Cc: Kees Cook , Elena Reshetova , x86@kernel.org, Andy Lutomirski , Peter Zijlstra , Catalin Marinas , Will Deacon , Mark Rutland , Alexander Potapenko , Alexander Popov , Ard Biesheuvel , Jann Horn , kernel-hardening@lists.openwall.com, linux-hardening@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Vlastimil Babka , David Hildenbrand , Mike Rapoport , Andrew Morton , Jonathan Corbet , Randy Dunlap Subject: [PATCH v5 5/7] x86/entry: Enable random_kstack_offset support Date: Tue, 9 Mar 2021 13:42:59 -0800 Message-Id: <20210309214301.678739-6-keescook@chromium.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210309214301.678739-1-keescook@chromium.org> References: <20210309214301.678739-1-keescook@chromium.org> MIME-Version: 1.0 X-Patch-Hashes: v=1; h=sha256; g=1a3993b6371bcc7c9fa1576e563a724a70c25875; i=np7yed3mY+gWIWkexmB7CyDLgwsIh0xV2RGaksJc7tI=; m=cc9SLz8pm+mdXOKZLHtRjH7FITDzwHCOKmwFrX1p7io=; p=UyRR1nzRrbUXeUU5ICay1xt2wYZVgu7b/Eh0FjkN2Hc= X-Patch-Sig: m=pgp; i=keescook@chromium.org; s=0x0x8972F4DFDC6DC026; b=iQIzBAABCgAdFiEEpcP2jyKd1g9yPm4TiXL039xtwCYFAmBH6+QACgkQiXL039xtwCYLvQ//ZVV jKPhAQU2IVFJZBsGYqSYa3g8Q8uXNjqNouwYZkGdZqCp2yYRsOzmXFeH0qyZJScVL7wk5Ocm/QTFW OZermriCXaGfjKrBkgIjBKWkpovFITXMioqiiczOh7oKZdo8pNVZ1ORyZoNOeQS3VBXKjN+07PE3h dMMzX56qSTd9WKxNPLKAo2kcBNV1vyrAW8pz2WcZvQEqImlpKpR4XxS7IYdK3YivXvt98Ny1/RRJS RfubXI54V4KwvZGGc13jwp1UsZfgnRAcxEHTSz+jlpK5CyZkfqgBNOQBIJd/bmUi8iMIPRB1fkHMY vTp2Nn3+PBSlIpGQiDyMoHW03a92fqONW5g98Ci048GC5vwFsjQbWB66SuAg/sf5qWZRmLYhxaHqR 8l56FZXXqzdjtLYuQvLxARNqgiYjjON93W1qxsHO1MoNsGbTGYOwvdHF+/70kZjRRS+4a4z21qQcL Rxvaadi1lQYfNlwgu0D7FoJcOxT12AJ8O7U1wLiIWroeJVxpYfq3sdQ5UT7Bgw/+Myc/ElGZhVK7m L0S/dtlbsTNa2yVUxTFGp4+UXIaH3CYIsAlrK63FimB7nbe4+a0mzl5DhJ+6+Of1ZGbvMlJnGyFsL 3EmbxC4ZdezBe/5xGxUELY+eR9ndl+C3u2gZzoCCKkJL+vEtcYX35II8VFuA2ab4= Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Allow for a randomized stack offset on a per-syscall basis, with roughly 5-6 bits of entropy, depending on compiler and word size. Since the method of offsetting uses macros, this cannot live in the common entry code (the stack offset needs to be retained for the life of the syscall, which means it needs to happen at the actual entry point). Signed-off-by: Kees Cook --- arch/x86/Kconfig | 1 + arch/x86/entry/common.c | 3 +++ arch/x86/include/asm/entry-common.h | 8 ++++++++ 3 files changed, 12 insertions(+) diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 2792879d398e..4b4ad8ec10d2 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -165,6 +165,7 @@ config X86 select HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD if X86_64 select HAVE_ARCH_USERFAULTFD_WP if X86_64 && USERFAULTFD select HAVE_ARCH_VMAP_STACK if X86_64 + select HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET select HAVE_ARCH_WITHIN_STACK_FRAMES select HAVE_ASM_MODVERSIONS select HAVE_CMPXCHG_DOUBLE diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c index a2433ae8a65e..810983d7c26f 100644 --- a/arch/x86/entry/common.c +++ b/arch/x86/entry/common.c @@ -38,6 +38,7 @@ #ifdef CONFIG_X86_64 __visible noinstr void do_syscall_64(unsigned long nr, struct pt_regs *regs) { + add_random_kstack_offset(); nr = syscall_enter_from_user_mode(regs, nr); instrumentation_begin(); @@ -83,6 +84,7 @@ __visible noinstr void do_int80_syscall_32(struct pt_regs *regs) { unsigned int nr = syscall_32_enter(regs); + add_random_kstack_offset(); /* * Subtlety here: if ptrace pokes something larger than 2^32-1 into * orig_ax, the unsigned int return value truncates it. This may @@ -102,6 +104,7 @@ static noinstr bool __do_fast_syscall_32(struct pt_regs *regs) unsigned int nr = syscall_32_enter(regs); int res; + add_random_kstack_offset(); /* * This cannot use syscall_enter_from_user_mode() as it has to * fetch EBP before invoking any of the syscall entry work diff --git a/arch/x86/include/asm/entry-common.h b/arch/x86/include/asm/entry-common.h index 2b87b191b3b8..8e41566e154a 100644 --- a/arch/x86/include/asm/entry-common.h +++ b/arch/x86/include/asm/entry-common.h @@ -2,6 +2,7 @@ #ifndef _ASM_X86_ENTRY_COMMON_H #define _ASM_X86_ENTRY_COMMON_H +#include #include #include @@ -70,6 +71,13 @@ static inline void arch_exit_to_user_mode_prepare(struct pt_regs *regs, */ current_thread_info()->status &= ~(TS_COMPAT | TS_I386_REGS_POKED); #endif + + /* + * x86_64 stack alignment means 3 bits are ignored, so keep + * the top 5 bits. x86_32 needs only 2 bits of alignment, so + * the top 6 bits will be used. + */ + choose_random_kstack_offset(rdtsc() & 0xFF); } #define arch_exit_to_user_mode_prepare arch_exit_to_user_mode_prepare -- 2.25.1