[PATCH V9 04/33] iov_iter: add __iovec_copy_to_user()

[Dave Kleikamp]

This patch adds __iovec_copy_to_user() which doesn't verify write access
to the user memory to be called from code where that verification has
already been done.

Signed-off-by: Dave Kleikamp <dave.kleik...@oracle.com>
Tested-by: Sedat Dilek <sedat.di...@gmail.com>
---
 fs/iov-iter.c      | 14 ++++++++++++--
 include/linux/fs.h |  4 +++-
 2 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/fs/iov-iter.c b/fs/iov-iter.c
index 0b2407e..6cecab4 100644
--- a/fs/iov-iter.c
+++ b/fs/iov-iter.c
@@ -19,7 +19,7 @@ static size_t __iovec_copy_to_user(char *vaddr, const struct 
iovec *iov,
                if (atomic)
                        left = __copy_to_user_inatomic(buf, vaddr, copy);
                else
-                       left = copy_to_user(buf, vaddr, copy);
+                       left = __copy_to_user(buf, vaddr, copy);
                copied += copy;
                bytes -= copy;
                vaddr += copy;
@@ -65,7 +65,7 @@ EXPORT_SYMBOL(iov_iter_copy_to_user_atomic);
  * The difference is that it attempts to resolve faults.
  * Page must not be locked.
  */
-size_t iov_iter_copy_to_user(struct page *page,
+size_t __iov_iter_copy_to_user(struct page *page,
                struct iov_iter *i, unsigned long offset, size_t bytes)
 {
        char *kaddr;
@@ -84,6 +84,16 @@ size_t iov_iter_copy_to_user(struct page *page,
        kunmap(page);
        return copied;
 }
+EXPORT_SYMBOL(__iov_iter_copy_to_user);
+
+size_t iov_iter_copy_to_user(struct page *page,
+               struct iov_iter *i, unsigned long offset, size_t bytes)
+{
+       might_sleep();
+       if (generic_segment_checks(i->iov, &i->nr_segs, &bytes, VERIFY_WRITE))
+               return 0;
+       return __iov_iter_copy_to_user(page, i, offset, bytes);
+}
 EXPORT_SYMBOL(iov_iter_copy_to_user);
 
 static size_t __iovec_copy_from_user(char *vaddr, const struct iovec *iov,
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 11647fe..b7a0ff8 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -297,7 +297,9 @@ struct iov_iter {
        size_t count;
 };
 
-size_t iov_iter_copy_to_user_atomic(struct page *page,
+size_t __iov_iter_copy_to_user_atomic(struct page *page,
+               struct iov_iter *i, unsigned long offset, size_t bytes);
+size_t __iov_iter_copy_to_user(struct page *page,
                struct iov_iter *i, unsigned long offset, size_t bytes);
 size_t iov_iter_copy_to_user(struct page *page,
                struct iov_iter *i, unsigned long offset, size_t bytes);
-- 
1.8.4

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