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@xxxxxxxxxxxx> AuthorDate: Tue, 29 Oct 2019 14:13:51 -07:00 Committer: Borislav Petkov <bp@xxxxxxx> 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@xxxxxxxxxxxx> Signed-off-by: Borislav Petkov <bp@xxxxxxx> Cc: Andy Lutomirski <luto@xxxxxxxxxx> Cc: Arnd Bergmann <arnd@xxxxxxxx> Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> Cc: Heiko Carstens <heiko.carstens@xxxxxxxxxx> Cc: "H. Peter Anvin" <hpa@xxxxxxxxx> Cc: Ingo Molnar <mingo@xxxxxxxxxx> Cc: linux-alpha@xxxxxxxxxxxxxxx Cc: linux-arch@xxxxxxxxxxxxxxx Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx Cc: linux-c6x-dev@xxxxxxxxxxxxx Cc: linux-ia64@xxxxxxxxxxxxxxx Cc: linuxppc-dev@xxxxxxxxxxxxxxxx Cc: linux-s390@xxxxxxxxxxxxxxx Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx> Cc: Michal Simek <monstr@xxxxxxxxx> Cc: Rick Edgecombe <rick.p.edgecombe@xxxxxxxxx> Cc: Ross Zwisler <zwisler@xxxxxxxxxxxx> Cc: Segher Boessenkool <segher@xxxxxxxxxxxxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: Thomas Lendacky <Thomas.Lendacky@xxxxxxx> Cc: Will Deacon <will@xxxxxxxxxx> Cc: x86-ml <x86@xxxxxxxxxx> Cc: Yoshinori Sato <ysato@xxxxxxxxxxxxxxxxxxxx> Link: https://lkml.kernel.org/r/20191029211351.13243-30-keescook@xxxxxxxxxxxx --- arch/x86/kernel/vmlinux.lds.S | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) 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 = .;
