diff options
Diffstat (limited to 'emulators')
| -rw-r--r-- | emulators/xen-kernel/Makefile | 5 | ||||
| -rw-r--r-- | emulators/xen-kernel/files/xsa204-4.7.patch | 69 |
2 files changed, 72 insertions, 2 deletions
diff --git a/emulators/xen-kernel/Makefile b/emulators/xen-kernel/Makefile index 196b66bf224a..68b92ac07625 100644 --- a/emulators/xen-kernel/Makefile +++ b/emulators/xen-kernel/Makefile @@ -3,7 +3,7 @@ PORTNAME= xen PKGNAMESUFFIX= -kernel PORTVERSION= 4.7.1 -PORTREVISION= 1 +PORTREVISION= 2 CATEGORIES= emulators MASTER_SITES= http://downloads.xenproject.org/release/xen/${PORTVERSION}/ @@ -45,7 +45,8 @@ EXTRA_PATCHES= ${FILESDIR}/0001-xen-logdirty-prevent-preemption-if-finished.patc ${FILESDIR}/xsa193-4.7.patch \ ${FILESDIR}/xsa194.patch \ ${FILESDIR}/xsa195.patch \ - ${FILESDIR}/xsa200-4.7.patch + ${FILESDIR}/xsa200-4.7.patch \ + ${FILESDIR}/xsa204-4.7.patch .include <bsd.port.options.mk> diff --git a/emulators/xen-kernel/files/xsa204-4.7.patch b/emulators/xen-kernel/files/xsa204-4.7.patch new file mode 100644 index 000000000000..ea41789a4b88 --- /dev/null +++ b/emulators/xen-kernel/files/xsa204-4.7.patch @@ -0,0 +1,69 @@ +From: Andrew Cooper <andrew.cooper3@citrix.com> +Date: Sun, 18 Dec 2016 15:42:59 +0000 +Subject: [PATCH] x86/emul: Correct the handling of eflags with SYSCALL + +A singlestep #DB is determined by the resulting eflags value from the +execution of SYSCALL, not the original eflags value. + +By using the original eflags value, we negate the guest kernels attempt to +protect itself from a privilege escalation by masking TF. + +Introduce a tf boolean and have the SYSCALL emulation recalculate it +after the instruction is complete. + +This is XSA-204 + +Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com> +Reviewed-by: Jan Beulich <jbeulich@suse.com> +--- + xen/arch/x86/x86_emulate/x86_emulate.c | 23 ++++++++++++++++++++--- + 1 file changed, 20 insertions(+), 3 deletions(-) + +diff --git a/xen/arch/x86/x86_emulate/x86_emulate.c b/xen/arch/x86/x86_emulate/x86_emulate.c +index bca7045..abe442e 100644 +--- a/xen/arch/x86/x86_emulate/x86_emulate.c ++++ b/xen/arch/x86/x86_emulate/x86_emulate.c +@@ -1582,6 +1582,7 @@ x86_emulate( + union vex vex = {}; + unsigned int op_bytes, def_op_bytes, ad_bytes, def_ad_bytes; + bool_t lock_prefix = 0; ++ bool_t tf = !!(ctxt->regs->eflags & EFLG_TF); + int override_seg = -1, rc = X86EMUL_OKAY; + struct operand src = { .reg = REG_POISON }; + struct operand dst = { .reg = REG_POISON }; +@@ -3910,9 +3911,8 @@ x86_emulate( + } + + no_writeback: +- /* Inject #DB if single-step tracing was enabled at instruction start. */ +- if ( (ctxt->regs->eflags & EFLG_TF) && (rc == X86EMUL_OKAY) && +- (ops->inject_hw_exception != NULL) ) ++ /* Should a singlestep #DB be raised? */ ++ if ( tf && (rc == X86EMUL_OKAY) && (ops->inject_hw_exception != NULL) ) + rc = ops->inject_hw_exception(EXC_DB, -1, ctxt) ? : X86EMUL_EXCEPTION; + + /* Commit shadow register state. */ +@@ -4143,6 +4143,23 @@ x86_emulate( + (rc = ops->write_segment(x86_seg_ss, &ss, ctxt)) ) + goto done; + ++ /* ++ * SYSCALL (unlike most instructions) evaluates its singlestep action ++ * based on the resulting EFLG_TF, not the starting EFLG_TF. ++ * ++ * As the #DB is raised after the CPL change and before the OS can ++ * switch stack, it is a large risk for privilege escalation. ++ * ++ * 64bit kernels should mask EFLG_TF in MSR_FMASK to avoid any ++ * vulnerability. Running the #DB handler on an IST stack is also a ++ * mitigation. ++ * ++ * 32bit kernels have no ability to mask EFLG_TF at all. Their only ++ * mitigation is to use a task gate for handling #DB (or to not use ++ * enable EFER.SCE to start with). ++ */ ++ tf = !!(_regs.eflags & EFLG_TF); ++ + break; + } + |