linux-kernel - [PATCH 17/41] copy_regset_to_user(): do all copyout at once.

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Message-Id: <20200629182628.529995-17-viro@ZenIV.linux.org.uk>
Date:   Mon, 29 Jun 2020 19:26:04 +0100
From:   Al Viro <viro@...IV.linux.org.uk>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org,
        David Miller <davem@...emloft.net>,
        Tony Luck <tony.luck@...el.com>, Will Deacon <will@...nel.org>
Subject: [PATCH 17/41] copy_regset_to_user(): do all copyout at once.

From: Al Viro <viro@...iv.linux.org.uk>

Turn copy_regset_to_user() into regset_get_alloc() + copy_to_user().
Now all ->get() calls have a kernel buffer as destination.

Note that we'd already eliminated the callers of copy_regset_to_user()
with non-zero offset; now that argument is simply unused.

Uninlined, while we are at it.

Signed-off-by: Al Viro <viro@...iv.linux.org.uk>
---
 include/linux/regset.h | 29 ++++-------------------------
 kernel/regset.c        | 26 ++++++++++++++++++++++++++
 2 files changed, 30 insertions(+), 25 deletions(-)

diff --git a/include/linux/regset.h b/include/linux/regset.h
index 968a032922d5..af57c1db1924 100644
--- a/include/linux/regset.h
+++ b/include/linux/regset.h
@@ -362,31 +362,10 @@ extern int regset_get_alloc(struct task_struct *target,
 			    unsigned int size,
 			    void **data);
 
-/**
- * copy_regset_to_user - fetch a thread's user_regset data into user memory
- * @target:	thread to be examined
- * @view:	&struct user_regset_view describing user thread machine state
- * @setno:	index in @view->regsets
- * @offset:	offset into the regset data, in bytes
- * @size:	amount of data to copy, in bytes
- * @data:	user-mode pointer to copy into
- */
-static inline int copy_regset_to_user(struct task_struct *target,
-				      const struct user_regset_view *view,
-				      unsigned int setno,
-				      unsigned int offset, unsigned int size,
-				      void __user *data)
-{
-	const struct user_regset *regset = &view->regsets[setno];
-
-	if (!regset->get)
-		return -EOPNOTSUPP;
-
-	if (!access_ok(data, size))
-		return -EFAULT;
-
-	return regset->get(target, regset, offset, size, NULL, data);
-}
+extern int copy_regset_to_user(struct task_struct *target,
+			       const struct user_regset_view *view,
+			       unsigned int setno, unsigned int offset,
+			       unsigned int size, void __user *data);
 
 /**
  * copy_regset_from_user - store into thread's user_regset data from user memory
diff --git a/kernel/regset.c b/kernel/regset.c
index 6b39fa0993ec..0a610983ce43 100644
--- a/kernel/regset.c
+++ b/kernel/regset.c
@@ -52,3 +52,29 @@ int regset_get_alloc(struct task_struct *target,
 	return __regset_get(target, regset, size, data);
 }
 EXPORT_SYMBOL(regset_get_alloc);
+
+/**
+ * copy_regset_to_user - fetch a thread's user_regset data into user memory
+ * @target:	thread to be examined
+ * @view:	&struct user_regset_view describing user thread machine state
+ * @setno:	index in @view->regsets
+ * @offset:	offset into the regset data, in bytes
+ * @size:	amount of data to copy, in bytes
+ * @data:	user-mode pointer to copy into
+ */
+int copy_regset_to_user(struct task_struct *target,
+			const struct user_regset_view *view,
+			unsigned int setno,
+			unsigned int offset, unsigned int size,
+			void __user *data)
+{
+	const struct user_regset *regset = &view->regsets[setno];
+	void *buf;
+	int ret;
+
+	ret = regset_get_alloc(target, regset, size, &buf);
+	if (ret > 0)
+		ret = copy_to_user(data, buf, ret) ? -EFAULT : 0;
+	kfree(buf);
+	return ret;
+}
-- 
2.11.0