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[tip:,x86/build] x86/vmlinux: Use INT3 instead of NOP for linker fill bytes

Message ID 157294604562.29376.16128940015704175473.tip-bot2@tip-bot2 (mailing list archive)
State Not Applicable
Headers show
Series [tip:,x86/build] x86/vmlinux: Use INT3 instead of NOP for linker fill bytes | expand

Checks

Context Check Description
snowpatch_ozlabs/apply_patch warning Failed to apply on branch powerpc/merge (b9ba205b97bda75388e4014914ae0bdc0022464c)
snowpatch_ozlabs/apply_patch warning Failed to apply on branch powerpc/next (d78d5dace5398b542fd5a21b50db6e88ce7d392e)
snowpatch_ozlabs/apply_patch warning Failed to apply on branch linus/master (a99d8080aaf358d5d23581244e5da23b35e340b9)
snowpatch_ozlabs/apply_patch warning Failed to apply on branch powerpc/fixes (7d6475051fb3d9339c5c760ed9883bc0a9048b21)
snowpatch_ozlabs/apply_patch warning Failed to apply on branch linux-next (51309b9d73f5de2d8cba2c850df0c3b5d9125bee)
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Commit Message

tip-bot2 for Linus Walleij Nov. 5, 2019, 9:27 a.m. UTC 
The following commit has been merged into the x86/build branch of tip:

Commit-ID:     7705dc8557973d8ad8f10840f61d8ec805695e9e
Gitweb:        https://git.kernel.org/tip/7705dc8557973d8ad8f10840f61d8ec805695e9e
Author:        Kees Cook <keescook@chromium.org>
AuthorDate:    Tue, 29 Oct 2019 14:13:51 -07:00
Committer:     Borislav Petkov <bp@suse.de>
CommitterDate: Mon, 04 Nov 2019 19:10:08 +01:00

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 | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
diff mbox series

Patch

diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
index b06d6e1..3a1a819 100644
--- a/arch/x86/kernel/vmlinux.lds.S
+++ b/arch/x86/kernel/vmlinux.lds.S
@@ -144,7 +144,7 @@  SECTIONS
 		*(.text.__x86.indirect_thunk)
 		__indirect_thunk_end = .;
 #endif
-	} :text = 0x9090
+	} :text =0xcccc
 
 	/* End of text section, which should occupy whole number of pages */
 	_etext = .;