From 102a0743326a03cd1a1202ceda21e175b7d3575c Mon Sep 17 00:00:00 2001
From: hc <hc@nodka.com>
Date: Tue, 20 Feb 2024 01:20:52 +0000
Subject: [PATCH] add new system file
---
kernel/lib/usercopy.c | 74 +++++++++++++++++++++++++++++++++++--
1 files changed, 70 insertions(+), 4 deletions(-)
diff --git a/kernel/lib/usercopy.c b/kernel/lib/usercopy.c
index 3744b2a..7ee63df 100644
--- a/kernel/lib/usercopy.c
+++ b/kernel/lib/usercopy.c
@@ -1,5 +1,9 @@
// SPDX-License-Identifier: GPL-2.0
+#include <linux/bitops.h>
+#include <linux/fault-inject-usercopy.h>
+#include <linux/instrumented.h>
#include <linux/uaccess.h>
+#include <linux/nospec.h>
/* out-of-line parts */
@@ -8,8 +12,14 @@
{
unsigned long res = n;
might_fault();
- if (likely(access_ok(VERIFY_READ, from, n))) {
- kasan_check_write(to, n);
+ if (!should_fail_usercopy() && likely(access_ok(from, n))) {
+ /*
+ * Ensure that bad access_ok() speculation will not
+ * lead to nasty side effects *after* the copy is
+ * finished:
+ */
+ barrier_nospec();
+ instrument_copy_from_user(to, from, n);
res = raw_copy_from_user(to, from, n);
}
if (unlikely(res))
@@ -23,11 +33,67 @@
unsigned long _copy_to_user(void __user *to, const void *from, unsigned long n)
{
might_fault();
- if (likely(access_ok(VERIFY_WRITE, to, n))) {
- kasan_check_read(from, n);
+ if (should_fail_usercopy())
+ return n;
+ if (likely(access_ok(to, n))) {
+ instrument_copy_to_user(to, from, n);
n = raw_copy_to_user(to, from, n);
}
return n;
}
EXPORT_SYMBOL(_copy_to_user);
#endif
+
+/**
+ * check_zeroed_user: check if a userspace buffer only contains zero bytes
+ * @from: Source address, in userspace.
+ * @size: Size of buffer.
+ *
+ * This is effectively shorthand for "memchr_inv(from, 0, size) == NULL" for
+ * userspace addresses (and is more efficient because we don't care where the
+ * first non-zero byte is).
+ *
+ * Returns:
+ * * 0: There were non-zero bytes present in the buffer.
+ * * 1: The buffer was full of zero bytes.
+ * * -EFAULT: access to userspace failed.
+ */
+int check_zeroed_user(const void __user *from, size_t size)
+{
+ unsigned long val;
+ uintptr_t align = (uintptr_t) from % sizeof(unsigned long);
+
+ if (unlikely(size == 0))
+ return 1;
+
+ from -= align;
+ size += align;
+
+ if (!user_read_access_begin(from, size))
+ return -EFAULT;
+
+ unsafe_get_user(val, (unsigned long __user *) from, err_fault);
+ if (align)
+ val &= ~aligned_byte_mask(align);
+
+ while (size > sizeof(unsigned long)) {
+ if (unlikely(val))
+ goto done;
+
+ from += sizeof(unsigned long);
+ size -= sizeof(unsigned long);
+
+ unsafe_get_user(val, (unsigned long __user *) from, err_fault);
+ }
+
+ if (size < sizeof(unsigned long))
+ val &= aligned_byte_mask(size);
+
+done:
+ user_read_access_end();
+ return (val == 0);
+err_fault:
+ user_read_access_end();
+ return -EFAULT;
+}
+EXPORT_SYMBOL(check_zeroed_user);
--
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