Commit-ID: 6dc936f175cc6d12a8eb14d29b87e9238e460383 Gitweb: https://git.kernel.org/tip/6dc936f175cc6d12a8eb14d29b87e9238e460383 Author: Dominik Brodowski <li...@dominikbrodowski.net> AuthorDate: Thu, 5 Apr 2018 11:53:06 +0200 Committer: Ingo Molnar <mi...@kernel.org> CommitDate: Thu, 5 Apr 2018 16:59:39 +0200
syscalls/x86: Extend register clearing on syscall entry to lower registers To reduce the chance that random user space content leaks down the call chain in registers, also clear lower registers on syscall entry: For 64-bit syscalls, extend the register clearing in PUSH_AND_CLEAR_REGS to %dx and %cx. This should not hurt at all, also on the other callers of that macro. We do not need to clear %rdi and %rsi for syscall entry, as those registers are used to pass the parameters to do_syscall_64(). For the 32-bit compat syscalls, do_int80_syscall_32() and do_fast_syscall_32() each only take one parameter. Therefore, extend the register clearing to %dx, %cx, and %si in entry_SYSCALL_compat and entry_INT80_compat. Signed-off-by: Dominik Brodowski <li...@dominikbrodowski.net> Acked-by: Linus Torvalds <torva...@linux-foundation.org> Cc: Al Viro <v...@zeniv.linux.org.uk> Cc: Andrew Morton <a...@linux-foundation.org> Cc: Andy Lutomirski <l...@kernel.org> Cc: Borislav Petkov <b...@alien8.de> Cc: Brian Gerst <brge...@gmail.com> Cc: Denys Vlasenko <dvlas...@redhat.com> Cc: H. Peter Anvin <h...@zytor.com> Cc: Josh Poimboeuf <jpoim...@redhat.com> Cc: Peter Zijlstra <pet...@infradead.org> Cc: Thomas Gleixner <t...@linutronix.de> Link: http://lkml.kernel.org/r/20180405095307.3730-8-li...@dominikbrodowski.net Signed-off-by: Ingo Molnar <mi...@kernel.org> --- arch/x86/entry/calling.h | 2 ++ arch/x86/entry/entry_64_compat.S | 6 ++++++ 2 files changed, 8 insertions(+) diff --git a/arch/x86/entry/calling.h b/arch/x86/entry/calling.h index be63330c5511..352e70cd33e8 100644 --- a/arch/x86/entry/calling.h +++ b/arch/x86/entry/calling.h @@ -114,7 +114,9 @@ For 32-bit we have the following conventions - kernel is built with pushq %rsi /* pt_regs->si */ .endif pushq \rdx /* pt_regs->dx */ + xorl %edx, %edx /* nospec dx */ pushq %rcx /* pt_regs->cx */ + xorl %ecx, %ecx /* nospec cx */ pushq \rax /* pt_regs->ax */ pushq %r8 /* pt_regs->r8 */ xorl %r8d, %r8d /* nospec r8 */ diff --git a/arch/x86/entry/entry_64_compat.S b/arch/x86/entry/entry_64_compat.S index 08425c42f8b7..9af927e59d49 100644 --- a/arch/x86/entry/entry_64_compat.S +++ b/arch/x86/entry/entry_64_compat.S @@ -220,8 +220,11 @@ GLOBAL(entry_SYSCALL_compat_after_hwframe) pushq %rax /* pt_regs->orig_ax */ pushq %rdi /* pt_regs->di */ pushq %rsi /* pt_regs->si */ + xorl %esi, %esi /* nospec si */ pushq %rdx /* pt_regs->dx */ + xorl %edx, %edx /* nospec dx */ pushq %rbp /* pt_regs->cx (stashed in bp) */ + xorl %ecx, %ecx /* nospec cx */ pushq $-ENOSYS /* pt_regs->ax */ pushq $0 /* pt_regs->r8 = 0 */ xorl %r8d, %r8d /* nospec r8 */ @@ -365,8 +368,11 @@ ENTRY(entry_INT80_compat) pushq (%rdi) /* pt_regs->di */ pushq %rsi /* pt_regs->si */ + xorl %esi, %esi /* nospec si */ pushq %rdx /* pt_regs->dx */ + xorl %edx, %edx /* nospec dx */ pushq %rcx /* pt_regs->cx */ + xorl %ecx, %ecx /* nospec cx */ pushq $-ENOSYS /* pt_regs->ax */ pushq $0 /* pt_regs->r8 = 0 */ xorl %r8d, %r8d /* nospec r8 */
