linux-kernel - [PATCH] x86/hyper-v: fix hypercalls with extended CPU ranges for TLB flushing

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Date:   Thu,  5 Oct 2017 10:34:29 -0300
From:   Marcelo Henrique Cerri <marcelo.cerri@...onical.com>
To:     "K. Y. Srinivasan" <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        devel@...uxdriverproject.org, linux-kernel@...r.kernel.org
Cc:     Josh Poulson <jopoulso@...rosoft.com>,
        Jork Loeser <Jork.Loeser@...rosoft.com>,
        Simon Xiao <sixiao@...rosoft.com>,
        Dexuan Cui <decui@...rosoft.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Marcelo Henrique Cerri <marcelo.cerri@...onical.com>
Subject: [PATCH] x86/hyper-v: fix hypercalls with extended CPU ranges for TLB flushing

Do not consider the fixed size of hv_vp_set when passing the variable
header size to hv_do_rep_hypercall().

The Hyper-V hypervisor specification states that for a hypercall with a
variable header only the size of the variable portion should be supplied
via the input control.

For HVCALL_FLUSH_VIRTUAL_ADDRESS_SPACE_EX/LIST_EX calls that means the
fixed portion of hv_vp_set should not be considered.

That fixes random failures of some applications that are unexpectedly
killed with SIGBUS or SIGSEGV.

Fixes: 628f54cc6451 ("x86/hyper-v: Support extended CPU ranges for TLB flush hypercalls")
Signed-off-by: Marcelo Henrique Cerri <marcelo.cerri@...onical.com>
---
 arch/x86/hyperv/mmu.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/x86/hyperv/mmu.c b/arch/x86/hyperv/mmu.c
index 39e7f6e50919..123d9b501108 100644
--- a/arch/x86/hyperv/mmu.c
+++ b/arch/x86/hyperv/mmu.c
@@ -222,18 +222,18 @@ static void hyperv_flush_tlb_others_ex(const struct cpumask *cpus,
 		flush->flags |= HV_FLUSH_NON_GLOBAL_MAPPINGS_ONLY;
 		status = hv_do_rep_hypercall(
 			HVCALL_FLUSH_VIRTUAL_ADDRESS_SPACE_EX,
-			0, nr_bank + 2, flush, NULL);
+			0, nr_bank, flush, NULL);
 	} else if (info->end &&
 		   ((info->end - info->start)/HV_TLB_FLUSH_UNIT) > max_gvas) {
 		status = hv_do_rep_hypercall(
 			HVCALL_FLUSH_VIRTUAL_ADDRESS_SPACE_EX,
-			0, nr_bank + 2, flush, NULL);
+			0, nr_bank, flush, NULL);
 	} else {
 		gva_n = fill_gva_list(flush->gva_list, nr_bank,
 				      info->start, info->end);
 		status = hv_do_rep_hypercall(
 			HVCALL_FLUSH_VIRTUAL_ADDRESS_LIST_EX,
-			gva_n, nr_bank + 2, flush, NULL);
+			gva_n, nr_bank, flush, NULL);
 	}
 
 	local_irq_restore(flags);
-- 
2.7.4