Merge branch 'for-davem' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

include/linux/uio.h

@@ -39,7 +39,10 @@ struct iov_iter {
 	};
 	union {
 		unsigned long nr_segs;
-		int idx;
+		struct {
+			int idx;
+			int start_idx;
+		};
 	};
 };
 
@@ -81,6 +84,7 @@ unsigned long iov_shorten(struct iovec *iov, unsigned long nr_segs, size_t to);
 size_t iov_iter_copy_from_user_atomic(struct page *page,
 		struct iov_iter *i, unsigned long offset, size_t bytes);
 void iov_iter_advance(struct iov_iter *i, size_t bytes);
+void iov_iter_revert(struct iov_iter *i, size_t bytes);
 int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes);
 size_t iov_iter_single_seg_count(const struct iov_iter *i);
 size_t copy_page_to_iter(struct page *page, size_t offset, size_t bytes,

lib/iov_iter.c

@@ -786,6 +786,68 @@ void iov_iter_advance(struct iov_iter *i, size_t size)
 }
 EXPORT_SYMBOL(iov_iter_advance);
 
+void iov_iter_revert(struct iov_iter *i, size_t unroll)
+{
+	if (!unroll)
+		return;
+	i->count += unroll;
+	if (unlikely(i->type & ITER_PIPE)) {
+		struct pipe_inode_info *pipe = i->pipe;
+		int idx = i->idx;
+		size_t off = i->iov_offset;
+		while (1) {
+			size_t n = off - pipe->bufs[idx].offset;
+			if (unroll < n) {
+				off -= (n - unroll);
+				break;
+			}
+			unroll -= n;
+			if (!unroll && idx == i->start_idx) {
+				off = 0;
+				break;
+			}
+			if (!idx--)
+				idx = pipe->buffers - 1;
+			off = pipe->bufs[idx].offset + pipe->bufs[idx].len;
+		}
+		i->iov_offset = off;
+		i->idx = idx;
+		pipe_truncate(i);
+		return;
+	}
+	if (unroll <= i->iov_offset) {
+		i->iov_offset -= unroll;
+		return;
+	}
+	unroll -= i->iov_offset;
+	if (i->type & ITER_BVEC) {
+		const struct bio_vec *bvec = i->bvec;
+		while (1) {
+			size_t n = (--bvec)->bv_len;
+			i->nr_segs++;
+			if (unroll <= n) {
+				i->bvec = bvec;
+				i->iov_offset = n - unroll;
+				return;
+			}
+			unroll -= n;
+		}
+	} else { /* same logics for iovec and kvec */
+		const struct iovec *iov = i->iov;
+		while (1) {
+			size_t n = (--iov)->iov_len;
+			i->nr_segs++;
+			if (unroll <= n) {
+				i->iov = iov;
+				i->iov_offset = n - unroll;
+				return;
+			}
+			unroll -= n;
+		}
+	}
+}
+EXPORT_SYMBOL(iov_iter_revert);
+
 /*
  * Return the count of just the current iov_iter segment.
  */
@@ -839,6 +901,7 @@ void iov_iter_pipe(struct iov_iter *i, int direction,
 	i->idx = (pipe->curbuf + pipe->nrbufs) & (pipe->buffers - 1);
 	i->iov_offset = 0;
 	i->count = count;
+	i->start_idx = i->idx;
 }
 EXPORT_SYMBOL(iov_iter_pipe);
 

net/core/datagram.c

@@ -398,7 +398,7 @@ int skb_copy_datagram_iter(const struct sk_buff *skb, int offset,
 			   struct iov_iter *to, int len)
 {
 	int start = skb_headlen(skb);
-	int i, copy = start - offset;
+	int i, copy = start - offset, start_off = offset, n;
 	struct sk_buff *frag_iter;
 
 	trace_skb_copy_datagram_iovec(skb, len);
@@ -407,11 +407,12 @@ int skb_copy_datagram_iter(const struct sk_buff *skb, int offset,
 	if (copy > 0) {
 		if (copy > len)
 			copy = len;
-		if (copy_to_iter(skb->data + offset, copy, to) != copy)
+		n = copy_to_iter(skb->data + offset, copy, to);
+		offset += n;
+		if (n != copy)
 			goto short_copy;
 		if ((len -= copy) == 0)
 			return 0;
-		offset += copy;
 	}
 
 	/* Copy paged appendix. Hmm... why does this look so complicated? */
@@ -425,13 +426,14 @@ int skb_copy_datagram_iter(const struct sk_buff *skb, int offset,
 		if ((copy = end - offset) > 0) {
 			if (copy > len)
 				copy = len;
-			if (copy_page_to_iter(skb_frag_page(frag),
+			n = copy_page_to_iter(skb_frag_page(frag),
 					      frag->page_offset + offset -
-					      start, copy, to) != copy)
+					      start, copy, to);
+			offset += n;
+			if (n != copy)
 				goto short_copy;
 			if (!(len -= copy))
 				return 0;
-			offset += copy;
 		}
 		start = end;
 	}
@@ -463,6 +465,7 @@ int skb_copy_datagram_iter(const struct sk_buff *skb, int offset,
 	 */
 
 fault:
+	iov_iter_revert(to, offset - start_off);
 	return -EFAULT;
 
 short_copy:
@@ -613,7 +616,7 @@ static int skb_copy_and_csum_datagram(const struct sk_buff *skb, int offset,
 				      __wsum *csump)
 {
 	int start = skb_headlen(skb);
-	int i, copy = start - offset;
+	int i, copy = start - offset, start_off = offset;
 	struct sk_buff *frag_iter;
 	int pos = 0;
 	int n;
@@ -623,11 +626,11 @@ static int skb_copy_and_csum_datagram(const struct sk_buff *skb, int offset,
 		if (copy > len)
 			copy = len;
 		n = csum_and_copy_to_iter(skb->data + offset, copy, csump, to);
+		offset += n;
 		if (n != copy)
 			goto fault;
 		if ((len -= copy) == 0)
 			return 0;
-		offset += copy;
 		pos = copy;
 	}
 
@@ -649,12 +652,12 @@ static int skb_copy_and_csum_datagram(const struct sk_buff *skb, int offset,
 						  offset - start, copy,
 						  &csum2, to);
 			kunmap(page);
+			offset += n;
 			if (n != copy)
 				goto fault;
 			*csump = csum_block_add(*csump, csum2, pos);
 			if (!(len -= copy))
 				return 0;
-			offset += copy;
 			pos += copy;
 		}
 		start = end;
@@ -687,6 +690,7 @@ static int skb_copy_and_csum_datagram(const struct sk_buff *skb, int offset,
 		return 0;
 
 fault:
+	iov_iter_revert(to, offset - start_off);
 	return -EFAULT;
 }
 
@@ -771,6 +775,7 @@ int skb_copy_and_csum_datagram_msg(struct sk_buff *skb,
 	}
 	return 0;
 csum_error:
+	iov_iter_revert(&msg->msg_iter, chunk);
 	return -EINVAL;
 fault:
 	return -EFAULT;