diff options
Diffstat (limited to 'system/xen/xsa/xsa201-2.patch')
| -rw-r--r-- | system/xen/xsa/xsa201-2.patch | 199 |
1 files changed, 0 insertions, 199 deletions
diff --git a/system/xen/xsa/xsa201-2.patch b/system/xen/xsa/xsa201-2.patch deleted file mode 100644 index 9bd1f8f89d..0000000000 --- a/system/xen/xsa/xsa201-2.patch +++ /dev/null @@ -1,199 +0,0 @@ -From: Wei Chen <Wei.Chen@arm.com> -Subject: arm64: handle async aborts delivered while at EL2 - -If EL1 generates an asynchronous abort and then traps into EL2 -(by HVC or IRQ) before the abort has been delivered, the hypervisor -could not catch it, because the PSTATE.A bit is masked all the time -in hypervisor. So this asynchronous abort may be slipped to next -running guest with PSTATE.A bit unmasked. - -In order to avoid this, it is necessary to take the abort at EL2, by -clearing the PSTATE.A bit. In this patch, we unmask the PSTATE.A bit -to open a window to catch guest-generated asynchronous abort in all -EL1 -> EL2 swich paths. If we catched such asynchronous abort in -checking window, the hyp_error exception will be triggered and the -abort source guest will be crashed. - -This is CVE-2016-9816, part of XSA-201. - -Signed-off-by: Wei Chen <Wei.Chen@arm.com> -Reviewed-by: Julien Grall <julien.grall@arm.com> - ---- a/xen/arch/arm/arm64/entry.S -+++ b/xen/arch/arm/arm64/entry.S -@@ -173,6 +173,43 @@ hyp_error_invalid: - entry hyp=1 - invalid BAD_ERROR - -+hyp_error: -+ /* -+ * Only two possibilities: -+ * 1) Either we come from the exit path, having just unmasked -+ * PSTATE.A: change the return code to an EL2 fault, and -+ * carry on, as we're already in a sane state to handle it. -+ * 2) Or we come from anywhere else, and that's a bug: we panic. -+ */ -+ entry hyp=1 -+ msr daifclr, #2 -+ -+ /* -+ * The ELR_EL2 may be modified by an interrupt, so we have to use the -+ * saved value in cpu_user_regs to check whether we come from 1) or -+ * not. -+ */ -+ ldr x0, [sp, #UREGS_PC] -+ adr x1, abort_guest_exit_start -+ cmp x0, x1 -+ adr x1, abort_guest_exit_end -+ ccmp x0, x1, #4, ne -+ mov x0, sp -+ mov x1, #BAD_ERROR -+ -+ /* -+ * Not equal, the exception come from 2). It's a bug, we have to -+ * panic the hypervisor. -+ */ -+ b.ne do_bad_mode -+ -+ /* -+ * Otherwise, the exception come from 1). It happened because of -+ * the guest. Crash this guest. -+ */ -+ bl do_trap_guest_error -+ exit hyp=1 -+ - /* Traps taken in Current EL with SP_ELx */ - hyp_sync: - entry hyp=1 -@@ -189,15 +226,29 @@ hyp_irq: - - guest_sync: - entry hyp=0, compat=0 -+ bl check_pending_vserror -+ /* -+ * If x0 is Non-zero, a vSError took place, the initial exception -+ * doesn't have any significance to be handled. Exit ASAP -+ */ -+ cbnz x0, 1f - msr daifclr, #2 - mov x0, sp - bl do_trap_hypervisor -+1: - exit hyp=0, compat=0 - - guest_irq: - entry hyp=0, compat=0 -+ bl check_pending_vserror -+ /* -+ * If x0 is Non-zero, a vSError took place, the initial exception -+ * doesn't have any significance to be handled. Exit ASAP -+ */ -+ cbnz x0, 1f - mov x0, sp - bl do_trap_irq -+1: - exit hyp=0, compat=0 - - guest_fiq_invalid: -@@ -213,15 +264,29 @@ guest_error: - - guest_sync_compat: - entry hyp=0, compat=1 -+ bl check_pending_vserror -+ /* -+ * If x0 is Non-zero, a vSError took place, the initial exception -+ * doesn't have any significance to be handled. Exit ASAP -+ */ -+ cbnz x0, 1f - msr daifclr, #2 - mov x0, sp - bl do_trap_hypervisor -+1: - exit hyp=0, compat=1 - - guest_irq_compat: - entry hyp=0, compat=1 -+ bl check_pending_vserror -+ /* -+ * If x0 is Non-zero, a vSError took place, the initial exception -+ * doesn't have any significance to be handled. Exit ASAP -+ */ -+ cbnz x0, 1f - mov x0, sp - bl do_trap_irq -+1: - exit hyp=0, compat=1 - - guest_fiq_invalid_compat: -@@ -270,6 +335,62 @@ return_from_trap: - eret - - /* -+ * This function is used to check pending virtual SError in the gap of -+ * EL1 -> EL2 world switch. -+ * The x0 register will be used to indicate the results of detection. -+ * x0 -- Non-zero indicates a pending virtual SError took place. -+ * x0 -- Zero indicates no pending virtual SError took place. -+ */ -+check_pending_vserror: -+ /* -+ * Save elr_el2 to check whether the pending SError exception takes -+ * place while we are doing this sync exception. -+ */ -+ mrs x0, elr_el2 -+ -+ /* Synchronize against in-flight ld/st */ -+ dsb sy -+ -+ /* -+ * Unmask PSTATE asynchronous abort bit. If there is a pending -+ * SError, the EL2 error exception will happen after PSTATE.A -+ * is cleared. -+ */ -+ msr daifclr, #4 -+ -+ /* -+ * This is our single instruction exception window. A pending -+ * SError is guaranteed to occur at the earliest when we unmask -+ * it, and at the latest just after the ISB. -+ * -+ * If a pending SError occurs, the program will jump to EL2 error -+ * exception handler, and the elr_el2 will be set to -+ * abort_guest_exit_start or abort_guest_exit_end. -+ */ -+abort_guest_exit_start: -+ -+ isb -+ -+abort_guest_exit_end: -+ /* Mask PSTATE asynchronous abort bit, close the checking window. */ -+ msr daifset, #4 -+ -+ /* -+ * Compare elr_el2 and the saved value to check whether we are -+ * returning from a valid exception caused by pending SError. -+ */ -+ mrs x1, elr_el2 -+ cmp x0, x1 -+ -+ /* -+ * Not equal, the pending SError exception took place, set -+ * x0 to non-zero. -+ */ -+ cset x0, ne -+ -+ ret -+ -+/* - * Exception vectors. - */ - .macro ventry label -@@ -287,7 +408,7 @@ ENTRY(hyp_traps_vector) - ventry hyp_sync // Synchronous EL2h - ventry hyp_irq // IRQ EL2h - ventry hyp_fiq_invalid // FIQ EL2h -- ventry hyp_error_invalid // Error EL2h -+ ventry hyp_error // Error EL2h - - ventry guest_sync // Synchronous 64-bit EL0/EL1 - ventry guest_irq // IRQ 64-bit EL0/EL1 |