]> git.baikalelectronics.ru Git - kernel.git/commit
x86/vmlinux: Use INT3 instead of NOP for linker fill bytes
authorKees Cook <keescook@chromium.org>
Tue, 29 Oct 2019 21:13:51 +0000 (14:13 -0700)
committerBorislav Petkov <bp@suse.de>
Mon, 4 Nov 2019 18:10:08 +0000 (19:10 +0100)
commit0c0f4d07e7b0a00f4fee4b9e4dc0098498c73fab
tree56e26e72fbf40763767e493f4bb429222ebd1250
parent45bead0e3449d6ca704bfdd901cf70f22a64277b
x86/vmlinux: Use INT3 instead of NOP for linker fill bytes

Instead of using 0x90 (NOP) to fill bytes between functions, which makes
it easier to sloppily target functions in function pointer overwrite
attacks, fill with 0xCC (INT3) to force a trap. Also drop the space
between "=" and the value to better match the binutils documentation

  https://sourceware.org/binutils/docs/ld/Output-Section-Fill.html#Output-Section-Fill

Example "objdump -d" before:

  ...
  ffffffff810001e0 <start_cpu0>:
  ffffffff810001e0:       48 8b 25 e1 b1 51 01    mov 0x151b1e1(%rip),%rsp        # ffffffff8251b3c8 <initial_stack>
  ffffffff810001e7:       e9 d5 fe ff ff          jmpq   ffffffff810000c1 <secondary_startup_64+0x91>
  ffffffff810001ec:       90                      nop
  ffffffff810001ed:       90                      nop
  ffffffff810001ee:       90                      nop
  ffffffff810001ef:       90                      nop

  ffffffff810001f0 <__startup_64>:
  ...

After:

  ...
  ffffffff810001e0 <start_cpu0>:
  ffffffff810001e0:       48 8b 25 41 79 53 01    mov 0x1537941(%rip),%rsp        # ffffffff82537b28 <initial_stack>
  ffffffff810001e7:       e9 d5 fe ff ff          jmpq   ffffffff810000c1 <secondary_startup_64+0x91>
  ffffffff810001ec:       cc                      int3
  ffffffff810001ed:       cc                      int3
  ffffffff810001ee:       cc                      int3
  ffffffff810001ef:       cc                      int3

  ffffffff810001f0 <__startup_64>:
  ...

Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: linux-alpha@vger.kernel.org
Cc: linux-arch@vger.kernel.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-c6x-dev@linux-c6x.org
Cc: linux-ia64@vger.kernel.org
Cc: linuxppc-dev@lists.ozlabs.org
Cc: linux-s390@vger.kernel.org
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Michal Simek <monstr@monstr.eu>
Cc: Rick Edgecombe <rick.p.edgecombe@intel.com>
Cc: Ross Zwisler <zwisler@chromium.org>
Cc: Segher Boessenkool <segher@kernel.crashing.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Thomas Lendacky <Thomas.Lendacky@amd.com>
Cc: Will Deacon <will@kernel.org>
Cc: x86-ml <x86@kernel.org>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Link: https://lkml.kernel.org/r/20191029211351.13243-30-keescook@chromium.org
arch/x86/kernel/vmlinux.lds.S