From 030300ebbb86c40c12db038714479d746167c767 Mon Sep 17 00:00:00 2001 From: Julien Grall Date: Tue, 26 May 2020 18:31:33 +0100 Subject: [PATCH] xen: Check the alignment of the offset pased via VCPUOP_register_vcpu_info Currently a guest is able to register any guest physical address to use for the vcpu_info structure as long as the structure can fits in the rest of the frame. This means a guest can provide an address that is not aligned to the natural alignment of the structure. On Arm 32-bit, unaligned access are completely forbidden by the hypervisor. This will result to a data abort which is fatal. On Arm 64-bit, unaligned access are only forbidden when used for atomic access. As the structure contains fields (such as evtchn_pending_self) that are updated using atomic operations, any unaligned access will be fatal as well. While the misalignment is only fatal on Arm, a generic check is added as an x86 guest shouldn't sensibly pass an unaligned address (this would result to a split lock). This is XSA-327. Reported-by: Julien Grall Signed-off-by: Julien Grall Reviewed-by: Andrew Cooper Reviewed-by: Stefano Stabellini --- xen/common/domain.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/xen/common/domain.c b/xen/common/domain.c index 7cc9526139a6..e9be05f1d05f 100644 --- a/xen/common/domain.c +++ b/xen/common/domain.c @@ -1227,10 +1227,20 @@ int map_vcpu_info(struct vcpu *v, unsigned long gfn, unsigned offset) void *mapping; vcpu_info_t *new_info; struct page_info *page; + unsigned int align; if ( offset > (PAGE_SIZE - sizeof(vcpu_info_t)) ) return -EINVAL; +#ifdef CONFIG_COMPAT + if ( has_32bit_shinfo(d) ) + align = alignof(new_info->compat); + else +#endif + align = alignof(*new_info); + if ( offset & (align - 1) ) + return -EINVAL; + if ( !mfn_eq(v->vcpu_info_mfn, INVALID_MFN) ) return -EINVAL; -- 2.17.1