Merge: iov_iter: fix ubuf iter

MR: https://gitlab.com/redhat/centos-stream/src/kernel/centos-stream-9/-/merge_requests/6763

Hello

JIRA: https://issues.redhat.com/browse/RHEL-87739

So far, we just run one partial backport on the following upstream PR to rhel9, and cause bug in code which depends on ITER_UBUF.

https://lore.kernel.org/all/f16053ea-d3b8-a8a2-0178-3981fea5a656@kernel.dk/

This MR pulls the other 4 missed patches to rhel9.

Signed-off-by: Ming Lei <ming.lei@redhat.com>

Approved-by: Jeff Moyer <jmoyer@redhat.com>
Approved-by: Ewan D. Milne <emilne@redhat.com>
Approved-by: CKI KWF Bot <cki-ci-bot+kwf-gitlab-com@redhat.com>
Approved-by: Rafael Aquini <raquini@redhat.com>

Merged-by: Augusto Caringi <acaringi@redhat.com>

Author: caringi

include/linux/uio.h

@@ -396,7 +396,8 @@ static inline void iov_iter_ubuf(struct iov_iter *i, unsigned int direction,
 		.user_backed = true,
 		.data_source = direction,
 		.ubuf = buf,
-		.count = count
+		.count = count,
+		.nr_segs = 1
 	};
 }
 /* Flags for iov_iter_get/extract_pages*() */

lib/iov_iter.c

@@ -1747,7 +1747,7 @@ const void *dup_iter(struct iov_iter *new, struct iov_iter *old, gfp_t flags)
 }
 EXPORT_SYMBOL(dup_iter);
 
-static int copy_compat_iovec_from_user(struct iovec *iov,
+static __noclone int copy_compat_iovec_from_user(struct iovec *iov,
 		const struct iovec __user *uvec, unsigned long nr_segs)
 {
 	const struct compat_iovec __user *uiov =
@@ -1779,7 +1779,7 @@ static int copy_compat_iovec_from_user(struct iovec *iov,
 	return ret;
 }
 
-static int copy_iovec_from_user(struct iovec *iov,
+static __noclone int copy_iovec_from_user(struct iovec *iov,
 		const struct iovec __user *uvec, unsigned long nr_segs)
 {
 	unsigned long seg;
@@ -1829,6 +1829,31 @@ struct iovec *iovec_from_user(const struct iovec __user *uvec,
 	return iov;
 }
 
+/*
+ * Single segment iovec supplied by the user, import it as ITER_UBUF.
+ */
+static ssize_t __import_iovec_ubuf(int type, const struct iovec __user *uvec,
+				   struct iovec **iovp, struct iov_iter *i,
+				   bool compat)
+{
+	struct iovec *iov = *iovp;
+	ssize_t ret;
+
+	*iovp = NULL;
+
+	if (compat)
+		ret = copy_compat_iovec_from_user(iov, uvec, 1);
+	else
+		ret = copy_iovec_from_user(iov, uvec, 1);
+	if (unlikely(ret))
+		return ret;
+
+	ret = import_ubuf(type, iov->iov_base, iov->iov_len, i);
+	if (unlikely(ret))
+		return ret;
+	return i->count;
+}
+
 ssize_t __import_iovec(int type, const struct iovec __user *uvec,
 		 unsigned nr_segs, unsigned fast_segs, struct iovec **iovp,
 		 struct iov_iter *i, bool compat)
@@ -1837,6 +1862,9 @@ ssize_t __import_iovec(int type, const struct iovec __user *uvec,
 	unsigned long seg;
 	struct iovec *iov;
 
+	if (nr_segs == 1)
+		return __import_iovec_ubuf(type, uvec, iovp, i, compat);
+
 	iov = iovec_from_user(uvec, nr_segs, fast_segs, *iovp, compat);
 	if (IS_ERR(iov)) {
 		*iovp = NULL;
@@ -1915,9 +1943,7 @@ int import_single_range(int rw, void __user *buf, size_t len,
 	if (unlikely(!access_ok(buf, len)))
 		return -EFAULT;
 
-	iov->iov_base = buf;
-	iov->iov_len = len;
-	iov_iter_init(i, rw, iov, 1, len);
+	iov_iter_ubuf(i, rw, buf, len);
 	return 0;
 }
 EXPORT_SYMBOL(import_single_range);