From 5bcab6a8a1d0855d44edf1590a6139e1f078e517 Mon Sep 17 00:00:00 2001 From: Jan Beulich Date: Tue, 16 Mar 2021 20:56:13 +0800 Subject: [PATCH] Xen/gnttab: handle p2m update errors on a per-slot basis stable inclusion from linux-4.19.179 commit 1a999d25ef536a14f6a7c25778836857adfba3f8 CVE: CVE-2021-28038 -------------------------------- commit 8310b77b48c5558c140e7a57a702e7819e62f04e upstream. Bailing immediately from set_foreign_p2m_mapping() upon a p2m updating error leaves the full batch in an ambiguous state as far as the caller is concerned. Instead flags respective slots as bad, unmapping what was mapped there right away. HYPERVISOR_grant_table_op()'s return value and the individual unmap slots' status fields get used only for a one-time - there's not much we can do in case of a failure. Note that there's no GNTST_enomem or alike, so GNTST_general_error gets used. The map ops' handle fields get overwritten just to be on the safe side. This is part of XSA-367. Cc: Signed-off-by: Jan Beulich Reviewed-by: Juergen Gross Link: https://lore.kernel.org/r/96cccf5d-e756-5f53-b91a-ea269bfb9be0@suse.com Signed-off-by: Juergen Gross Signed-off-by: Greg Kroah-Hartman Signed-off-by: Yang Yingliang Reviewed-by: Xiu Jianfeng Signed-off-by: Yang Yingliang Acked-by: Xie XiuQi Signed-off-by: Cheng Jian --- arch/arm/xen/p2m.c | 35 +++++++++++++++++++++++++++++++---- arch/x86/xen/p2m.c | 44 +++++++++++++++++++++++++++++++++++++++++--- 2 files changed, 72 insertions(+), 7 deletions(-) diff --git a/arch/arm/xen/p2m.c b/arch/arm/xen/p2m.c index ce538c51fa3f..8a8a388549e7 100644 --- a/arch/arm/xen/p2m.c +++ b/arch/arm/xen/p2m.c @@ -91,12 +91,39 @@ int set_foreign_p2m_mapping(struct gnttab_map_grant_ref *map_ops, int i; for (i = 0; i < count; i++) { + struct gnttab_unmap_grant_ref unmap; + int rc; + if (map_ops[i].status) continue; - if (unlikely(!set_phys_to_machine(map_ops[i].host_addr >> XEN_PAGE_SHIFT, - map_ops[i].dev_bus_addr >> XEN_PAGE_SHIFT))) { - return -ENOMEM; - } + if (likely(set_phys_to_machine(map_ops[i].host_addr >> XEN_PAGE_SHIFT, + map_ops[i].dev_bus_addr >> XEN_PAGE_SHIFT))) + continue; + + /* + * Signal an error for this slot. This in turn requires + * immediate unmapping. + */ + map_ops[i].status = GNTST_general_error; + unmap.host_addr = map_ops[i].host_addr, + unmap.handle = map_ops[i].handle; + map_ops[i].handle = ~0; + if (map_ops[i].flags & GNTMAP_device_map) + unmap.dev_bus_addr = map_ops[i].dev_bus_addr; + else + unmap.dev_bus_addr = 0; + + /* + * Pre-populate the status field, to be recognizable in + * the log message below. + */ + unmap.status = 1; + + rc = HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, + &unmap, 1); + if (rc || unmap.status != GNTST_okay) + pr_err_once("gnttab unmap failed: rc=%d st=%d\n", + rc, unmap.status); } return 0; diff --git a/arch/x86/xen/p2m.c b/arch/x86/xen/p2m.c index e8ef994c7243..82577eec6d0a 100644 --- a/arch/x86/xen/p2m.c +++ b/arch/x86/xen/p2m.c @@ -706,6 +706,8 @@ int set_foreign_p2m_mapping(struct gnttab_map_grant_ref *map_ops, for (i = 0; i < count; i++) { unsigned long mfn, pfn; + struct gnttab_unmap_grant_ref unmap[2]; + int rc; /* Do not add to override if the map failed. */ if (map_ops[i].status != GNTST_okay || @@ -723,10 +725,46 @@ int set_foreign_p2m_mapping(struct gnttab_map_grant_ref *map_ops, WARN(pfn_to_mfn(pfn) != INVALID_P2M_ENTRY, "page must be ballooned"); - if (unlikely(!set_phys_to_machine(pfn, FOREIGN_FRAME(mfn)))) { - ret = -ENOMEM; - goto out; + if (likely(set_phys_to_machine(pfn, FOREIGN_FRAME(mfn)))) + continue; + + /* + * Signal an error for this slot. This in turn requires + * immediate unmapping. + */ + map_ops[i].status = GNTST_general_error; + unmap[0].host_addr = map_ops[i].host_addr, + unmap[0].handle = map_ops[i].handle; + map_ops[i].handle = ~0; + if (map_ops[i].flags & GNTMAP_device_map) + unmap[0].dev_bus_addr = map_ops[i].dev_bus_addr; + else + unmap[0].dev_bus_addr = 0; + + if (kmap_ops) { + kmap_ops[i].status = GNTST_general_error; + unmap[1].host_addr = kmap_ops[i].host_addr, + unmap[1].handle = kmap_ops[i].handle; + kmap_ops[i].handle = ~0; + if (kmap_ops[i].flags & GNTMAP_device_map) + unmap[1].dev_bus_addr = kmap_ops[i].dev_bus_addr; + else + unmap[1].dev_bus_addr = 0; } + + /* + * Pre-populate both status fields, to be recognizable in + * the log message below. + */ + unmap[0].status = 1; + unmap[1].status = 1; + + rc = HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, + unmap, 1 + !!kmap_ops); + if (rc || unmap[0].status != GNTST_okay || + unmap[1].status != GNTST_okay) + pr_err_once("gnttab unmap failed: rc=%d st0=%d st1=%d\n", + rc, unmap[0].status, unmap[1].status); } out: -- GitLab