linux-kernel - [RFC PATCH v1 25/37] KVM: selftests: guest_memfd: Test that truncation does not change shared/private status

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <00b93a008a75a345f71b61ac67a2ffa068bc67d7.1760731772.git.ackerleytng@google.com>
Date: Fri, 17 Oct 2025 13:12:06 -0700
From: Ackerley Tng <ackerleytng@...gle.com>
To: cgroups@...r.kernel.org, kvm@...r.kernel.org, linux-doc@...r.kernel.org, 
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-kselftest@...r.kernel.org, linux-mm@...ck.org, 
	linux-trace-kernel@...r.kernel.org, x86@...nel.org
Cc: ackerleytng@...gle.com, akpm@...ux-foundation.org, 
	binbin.wu@...ux.intel.com, bp@...en8.de, brauner@...nel.org, 
	chao.p.peng@...el.com, chenhuacai@...nel.org, corbet@....net, 
	dave.hansen@...el.com, dave.hansen@...ux.intel.com, david@...hat.com, 
	dmatlack@...gle.com, erdemaktas@...gle.com, fan.du@...el.com, fvdl@...gle.com, 
	haibo1.xu@...el.com, hannes@...xchg.org, hch@...radead.org, hpa@...or.com, 
	hughd@...gle.com, ira.weiny@...el.com, isaku.yamahata@...el.com, jack@...e.cz, 
	james.morse@....com, jarkko@...nel.org, jgg@...pe.ca, jgowans@...zon.com, 
	jhubbard@...dia.com, jroedel@...e.de, jthoughton@...gle.com, 
	jun.miao@...el.com, kai.huang@...el.com, keirf@...gle.com, 
	kent.overstreet@...ux.dev, liam.merwick@...cle.com, 
	maciej.wieczor-retman@...el.com, mail@...iej.szmigiero.name, 
	maobibo@...ngson.cn, mathieu.desnoyers@...icios.com, maz@...nel.org, 
	mhiramat@...nel.org, mhocko@...nel.org, mic@...ikod.net, michael.roth@....com, 
	mingo@...hat.com, mlevitsk@...hat.com, mpe@...erman.id.au, 
	muchun.song@...ux.dev, nikunj@....com, nsaenz@...zon.es, 
	oliver.upton@...ux.dev, palmer@...belt.com, pankaj.gupta@....com, 
	paul.walmsley@...ive.com, pbonzini@...hat.com, peterx@...hat.com, 
	pgonda@...gle.com, prsampat@....com, pvorel@...e.cz, qperret@...gle.com, 
	richard.weiyang@...il.com, rick.p.edgecombe@...el.com, rientjes@...gle.com, 
	rostedt@...dmis.org, roypat@...zon.co.uk, rppt@...nel.org, seanjc@...gle.com, 
	shakeel.butt@...ux.dev, shuah@...nel.org, steven.price@....com, 
	steven.sistare@...cle.com, suzuki.poulose@....com, tabba@...gle.com, 
	tglx@...utronix.de, thomas.lendacky@....com, vannapurve@...gle.com, 
	vbabka@...e.cz, viro@...iv.linux.org.uk, vkuznets@...hat.com, 
	wei.w.wang@...el.com, will@...nel.org, willy@...radead.org, wyihan@...gle.com, 
	xiaoyao.li@...el.com, yan.y.zhao@...el.com, yilun.xu@...el.com, 
	yuzenghui@...wei.com, zhiquan1.li@...el.com
Subject: [RFC PATCH v1 25/37] KVM: selftests: guest_memfd: Test that
 truncation does not change shared/private status

Add a test to verify that deallocating a page in a guest memfd region via
fallocate() with FALLOC_FL_PUNCH_HOLE does not alter the shared or private
status of the corresponding memory range.

When a page backing a guest memfd mapping is deallocated, e.g., by punching
a hole or truncating the file, and then subsequently faulted back in, the
new page must inherit the correct shared/private status tracked by
guest_memfd.

Signed-off-by: Ackerley Tng <ackerleytng@...gle.com>
Co-developed-by: Sean Christopherson <seanjc@...gle.com>
Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 .../selftests/kvm/guest_memfd_conversions_test.c   | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/tools/testing/selftests/kvm/guest_memfd_conversions_test.c b/tools/testing/selftests/kvm/guest_memfd_conversions_test.c
index 43efe4af1403c..907d415d72315 100644
--- a/tools/testing/selftests/kvm/guest_memfd_conversions_test.c
+++ b/tools/testing/selftests/kvm/guest_memfd_conversions_test.c
@@ -10,6 +10,7 @@
 #include <linux/sizes.h>
 
 #include "kvm_util.h"
+#include "kvm_syscalls.h"
 #include "kselftest_harness.h"
 #include "test_util.h"
 #include "ucall_common.h"
@@ -316,6 +317,19 @@ GMEM_CONVERSION_MULTIPAGE_TEST_INIT_SHARED(unallocated_folios, 8)
 		test_convert_to_shared(t, i, 'B', 'C', 'D');
 }
 
+/* Truncation should not affect shared/private status. */
+GMEM_CONVERSION_TEST_INIT_SHARED(truncate)
+{
+	host_do_rmw(t->mem, 0, 0, 'A');
+	kvm_fallocate(t->gmem_fd, FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE, 0, page_size);
+	host_do_rmw(t->mem, 0, 0, 'A');
+
+	test_convert_to_private(t, 0, 'A', 'B');
+
+	kvm_fallocate(t->gmem_fd, FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE, 0, page_size);
+	test_private(t, 0, 0, 'A');
+}
+
 int main(int argc, char *argv[])
 {
 	TEST_REQUIRE(kvm_check_cap(KVM_CAP_VM_TYPES) & BIT(KVM_X86_SW_PROTECTED_VM));
-- 
2.51.0.858.gf9c4a03a3a-goog