Date: Tue, 5 Feb 2019 17:49:27 +0000 (UTC) From: Konstantin Belousov <kib@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r343780 - head/sys/amd64/amd64 Message-ID: <201902051749.x15HnRqr035442@repo.freebsd.org>
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Author: kib Date: Tue Feb 5 17:49:27 2019 New Revision: 343780 URL: https://svnweb.freebsd.org/changeset/base/343780 Log: amd64: clear callee-preserved registers on syscall exit. %r8, %r10, and on non-KPTI configuration %r9 were not restored on fast return from a syscall. Reviewed by: markj Approved by: so Security: CVE-2019-5595 Sponsored by: The FreeBSD Foundation MFC after: 0 minutes Modified: head/sys/amd64/amd64/exception.S Modified: head/sys/amd64/amd64/exception.S ============================================================================== --- head/sys/amd64/amd64/exception.S Tue Feb 5 17:17:12 2019 (r343779) +++ head/sys/amd64/amd64/exception.S Tue Feb 5 17:49:27 2019 (r343780) @@ -521,12 +521,14 @@ fast_syscall_common: movq TF_RFLAGS(%rsp),%r11 /* original %rflags */ movq TF_RIP(%rsp),%rcx /* original %rip */ movq TF_RSP(%rsp),%rsp /* user stack pointer */ + xorl %r8d,%r8d /* zero the rest of GPRs */ + xorl %r10d,%r10d cmpq $~0,PCPU(UCR3) je 2f movq PCPU(UCR3),%r9 movq %r9,%cr3 - xorl %r9d,%r9d -2: swapgs +2: xorl %r9d,%r9d + swapgs sysretq 3: /* AST scheduled. */
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