# Commit 29bcf64ce8bc0b1b7aacd00c8668f255c4f0686c # Date 2015-10-29 13:31:10 +0100 # Author Julien Grall # Committer Jan Beulich arm: Support hypercall_create_continuation for multicall Multicall for ARM has been supported since commit f0dbdc6 "xen: arm: fully implement multicall interface.". Although, if an hypercall in multicall requires preemption, it will crash the host: (XEN) Xen BUG at domain.c:347 (XEN) ----[ Xen-4.7-unstable arm64 debug=y Tainted: C ]---- [...] (XEN) Xen call trace: (XEN) [<00000000002420cc>] hypercall_create_continuation+0x64/0x380 (PC) (XEN) [<0000000000217274>] do_memory_op+0x1b00/0x2334 (LR) (XEN) [<0000000000250d2c>] do_multicall_call+0x114/0x124 (XEN) [<0000000000217ff0>] do_multicall+0x17c/0x23c (XEN) [<000000000024f97c>] do_trap_hypercall+0x90/0x12c (XEN) [<0000000000251ca8>] do_trap_hypervisor+0xd2c/0x1ba4 (XEN) [<00000000002582cc>] guest_sync+0x88/0xb8 (XEN) (XEN) (XEN) **************************************** (XEN) Panic on CPU 5: (XEN) Xen BUG at domain.c:347 (XEN) **************************************** (XEN) (XEN) Manual reset required ('noreboot' specified) Looking to the code, the support of multicall looks valid to me, as we only need to fill call.args[...]. So drop the BUG(); This is CVE-2015-7812 / XSA-145. Signed-off-by: Julien Grall Acked-by: Ian Campbell --- a/xen/arch/arm/domain.c +++ b/xen/arch/arm/domain.c @@ -344,8 +344,6 @@ unsigned long hypercall_create_continuat if ( test_bit(_MCSF_in_multicall, &mcs->flags) ) { - BUG(); /* XXX multicalls not implemented yet. */ - __set_bit(_MCSF_call_preempted, &mcs->flags); for ( i = 0; *p != '\0'; i++ )