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Commit7705dc8
x86/vmlinux: Use INT3 instead of NOP for linker fill bytes
Instead of using 0x90 (NOP) to fill bytes between functions, which makesit easier to sloppily target functions in function pointer overwriteattacks, fill with 0xCC (INT3) to force a trap. Also drop the spacebetween "=" and the value to better match the binutils documentationhttps://sourceware.org/binutils/docs/ld/Output-Section-Fill.html#Output-Section-FillExample "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.orgCc: linux-arch@vger.kernel.orgCc: linux-arm-kernel@lists.infradead.orgCc: linux-c6x-dev@linux-c6x.orgCc: linux-ia64@vger.kernel.orgCc: linuxppc-dev@lists.ozlabs.orgCc: linux-s390@vger.kernel.orgCc: 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.org1 parenta329975 commit7705dc8
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