Commit-ID: 2fbd7af5af8665d18bcefae3e9700be07e22b681 Gitweb: https://git.kernel.org/tip/2fbd7af5af8665d18bcefae3e9700be07e22b681 Author: Dan Williams <dan.j.willi...@intel.com> AuthorDate: Mon, 29 Jan 2018 17:02:59 -0800 Committer: Thomas Gleixner <t...@linutronix.de> CommitDate: Tue, 30 Jan 2018 21:54:31 +0100
x86/syscall: Sanitize syscall table de-references under speculation The syscall table base is a user controlled function pointer in kernel space. Use array_index_nospec() to prevent any out of bounds speculation. While retpoline prevents speculating into a userspace directed target it does not stop the pointer de-reference, the concern is leaking memory relative to the syscall table base, by observing instruction cache behavior. Reported-by: Linus Torvalds <torva...@linux-foundation.org> Signed-off-by: Dan Williams <dan.j.willi...@intel.com> Signed-off-by: Thomas Gleixner <t...@linutronix.de> Cc: linux-a...@vger.kernel.org Cc: kernel-harden...@lists.openwall.com Cc: gre...@linuxfoundation.org Cc: Andy Lutomirski <l...@kernel.org> Cc: a...@linux.intel.com Link: https://lkml.kernel.org/r/151727417984.33451.1216731042505722161.st...@dwillia2-desk3.amr.corp.intel.com --- arch/x86/entry/common.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c index 9908134..21dbdf0 100644 --- a/arch/x86/entry/common.c +++ b/arch/x86/entry/common.c @@ -21,6 +21,7 @@ #include <linux/export.h> #include <linux/context_tracking.h> #include <linux/user-return-notifier.h> +#include <linux/nospec.h> #include <linux/uprobes.h> #include <linux/livepatch.h> #include <linux/syscalls.h> @@ -282,7 +283,8 @@ __visible void do_syscall_64(struct pt_regs *regs) * regs->orig_ax, which changes the behavior of some syscalls. */ if (likely((nr & __SYSCALL_MASK) < NR_syscalls)) { - regs->ax = sys_call_table[nr & __SYSCALL_MASK]( + nr = array_index_nospec(nr & __SYSCALL_MASK, NR_syscalls); + regs->ax = sys_call_table[nr]( regs->di, regs->si, regs->dx, regs->r10, regs->r8, regs->r9); } @@ -318,6 +320,7 @@ static __always_inline void do_syscall_32_irqs_on(struct pt_regs *regs) } if (likely(nr < IA32_NR_syscalls)) { + nr = array_index_nospec(nr, IA32_NR_syscalls); /* * It's possible that a 32-bit syscall implementation * takes a 64-bit parameter but nonetheless assumes that
