From: Paolo Bonzini <pbonzini@redhat.com>
To: linux-kernel@vger.kernel.org, kvm@vger.kernel.org
Cc: vkuznets@redhat.com, Joerg Roedel <jroedel@suse.de>
Subject: [PATCH 22/24] uaccess: add memzero_user
Date: Wed, 20 May 2020 13:21:43 -0400 [thread overview]
Message-ID: <20200520172145.23284-23-pbonzini@redhat.com> (raw)
In-Reply-To: <20200520172145.23284-1-pbonzini@redhat.com>
This will be used from KVM. Add it to lib/ so that everyone can use it.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
include/linux/uaccess.h | 1 +
lib/usercopy.c | 63 +++++++++++++++++++++++++++++++++++++++++
2 files changed, 64 insertions(+)
diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h
index 67f016010aad..bd8c85b50e67 100644
--- a/include/linux/uaccess.h
+++ b/include/linux/uaccess.h
@@ -232,6 +232,7 @@ __copy_from_user_inatomic_nocache(void *to, const void __user *from,
#endif /* ARCH_HAS_NOCACHE_UACCESS */
extern __must_check int check_zeroed_user(const void __user *from, size_t size);
+extern __must_check int memzero_user(void __user *from, size_t size);
/**
* copy_struct_from_user: copy a struct from userspace
diff --git a/lib/usercopy.c b/lib/usercopy.c
index cbb4d9ec00f2..82997862bf02 100644
--- a/lib/usercopy.c
+++ b/lib/usercopy.c
@@ -33,6 +33,69 @@ unsigned long _copy_to_user(void __user *to, const void *from, unsigned long n)
EXPORT_SYMBOL(_copy_to_user);
#endif
+/**
+ * memzero_user: write zero bytes to a userspace buffer
+ * @from: Source address, in userspace.
+ * @size: Size of buffer.
+ *
+ * This is effectively shorthand for "memset(from, 0, size)" for
+ * userspace addresses.
+ *
+ * Returns:
+ * * 0: zeroes have been written to the buffer
+ * * -EFAULT: access to userspace failed.
+ */
+int memzero_user(void __user *from, size_t size)
+{
+ unsigned long val = 0;
+ unsigned long mask = 0;
+ uintptr_t align = (uintptr_t) from % sizeof(unsigned long);
+
+ if (unlikely(size == 0))
+ return 0;
+
+ from -= align;
+ size += align;
+
+ if (!user_access_begin(from, ALIGN_UP(size, sizeof(unsigned long))))
+ return -EFAULT;
+
+ if (align) {
+ unsafe_get_user(val, (unsigned long __user *) from, err_fault);
+ /* Prepare a mask to keep the first "align" bytes. */
+ mask = aligned_byte_mask(align);
+ }
+
+ if (size >= sizeof(unsigned long)) {
+ /* The mask only applies to the first full word. */
+ val &= mask;
+ mask = 0;
+ do {
+ unsafe_put_user(val, (unsigned long __user *) from, err_fault);
+ from += sizeof(unsigned long);
+ size -= sizeof(unsigned long);
+ val = 0;
+ } while (size >= sizeof(unsigned long));
+
+ if (!size)
+ goto done;
+ unsafe_get_user(val, (unsigned long __user *) from, err_fault);
+ }
+
+ /* Bytes after the first "size" have to be kept too. */
+ mask |= ~aligned_byte_mask(size);
+ val &= mask;
+ unsafe_put_user(val, (unsigned long __user *) from, err_fault);
+
+done:
+ user_access_end();
+ return 0;
+err_fault:
+ user_access_end();
+ return -EFAULT;
+}
+EXPORT_SYMBOL(memzero_user);
+
/**
* check_zeroed_user: check if a userspace buffer only contains zero bytes
* @from: Source address, in userspace.
--
2.18.2
next prev parent reply other threads:[~2020-05-20 17:22 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-20 17:21 [PATCH 00/24] KVM: nSVM: event fixes and migration support Paolo Bonzini
2020-05-20 17:21 ` [PATCH 01/24] KVM: nSVM: fix condition for filtering async PF Paolo Bonzini
2020-05-26 0:23 ` Sasha Levin
2020-05-20 17:21 ` [PATCH 02/24] KVM: nSVM: leave ASID aside in copy_vmcb_control_area Paolo Bonzini
2020-05-26 0:23 ` Sasha Levin
2020-05-20 17:21 ` [PATCH 03/24] KVM: nSVM: inject exceptions via svm_check_nested_events Paolo Bonzini
2020-05-20 17:21 ` [PATCH 04/24] KVM: nSVM: remove exit_required Paolo Bonzini
2020-05-20 17:21 ` [PATCH 05/24] KVM: nSVM: correctly inject INIT vmexits Paolo Bonzini
2020-05-20 17:21 ` [PATCH 06/24] KVM: nSVM: move map argument out of enter_svm_guest_mode Paolo Bonzini
2020-05-20 17:21 ` [PATCH 07/24] KVM: nSVM: extract load_nested_vmcb_control Paolo Bonzini
2020-05-20 17:21 ` [PATCH 08/24] KVM: nSVM: extract preparation of VMCB for nested run Paolo Bonzini
2020-05-20 17:21 ` [PATCH 09/24] KVM: nSVM: clean up tsc_offset update Paolo Bonzini
2020-05-20 17:21 ` [PATCH 10/24] KVM: nSVM: pass vmcb_control_area to copy_vmcb_control_area Paolo Bonzini
2020-05-20 17:21 ` [PATCH 11/24] KVM: nSVM: remove trailing padding for struct vmcb_control_area Paolo Bonzini
2020-05-20 17:21 ` [PATCH 12/24] KVM: nSVM: save all control fields in svm->nested Paolo Bonzini
2020-05-20 17:21 ` [PATCH 13/24] KVM: nSVM: do not reload pause filter fields from VMCB Paolo Bonzini
2020-05-20 17:21 ` [PATCH 14/24] KVM: nSVM: remove HF_VINTR_MASK Paolo Bonzini
2020-05-20 17:21 ` [PATCH 15/24] KVM: nSVM: remove HF_HIF_MASK Paolo Bonzini
2020-05-20 17:21 ` [PATCH 16/24] KVM: nSVM: split nested_vmcb_check_controls Paolo Bonzini
2020-05-20 17:21 ` [PATCH 17/24] KVM: nSVM: do all MMU switch work in init/uninit functions Paolo Bonzini
2020-05-20 17:21 ` [PATCH 18/24] KVM: nSVM: leave guest mode when clearing EFER.SVME Paolo Bonzini
2020-05-20 17:21 ` [PATCH 19/24] KVM: nSVM: extract svm_set_gif Paolo Bonzini
2020-05-20 17:21 ` [PATCH 20/24] KVM: MMU: pass arbitrary CR0/CR4/EFER to kvm_init_shadow_mmu Paolo Bonzini
2020-05-20 17:21 ` [PATCH 21/24] KVM: x86: always update CR3 in VMCB Paolo Bonzini
2020-05-20 18:22 ` Sean Christopherson
2020-05-20 20:14 ` Paolo Bonzini
2020-05-22 22:47 ` Sean Christopherson
2020-05-23 7:07 ` Paolo Bonzini
2020-05-20 18:24 ` Sean Christopherson
2020-05-20 17:21 ` Paolo Bonzini [this message]
2020-05-20 20:40 ` [PATCH 22/24] uaccess: add memzero_user Christoph Hellwig
2020-05-20 20:50 ` Al Viro
2020-05-20 21:13 ` Paolo Bonzini
2020-05-20 21:28 ` Al Viro
2020-05-20 21:33 ` Paolo Bonzini
2020-05-20 17:21 ` [PATCH 23/24] selftests: kvm: add a SVM version of state-test Paolo Bonzini
2020-05-20 17:21 ` [PATCH 24/24] KVM: nSVM: implement KVM_GET_NESTED_STATE and KVM_SET_NESTED_STATE Paolo Bonzini
2020-05-20 19:24 ` [PATCH 00/24] KVM: nSVM: event fixes and migration support Maxim Levitsky
2020-05-20 20:42 ` Paolo Bonzini
2020-05-20 21:08 ` Maxim Levitsky
2020-05-20 21:15 ` Paolo Bonzini
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