Re: [syzbot] [syzbot] [fs?] general protection fault in iter_file_splice_write

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Subject: [syzbot] [fs?] general protection fault in iter_file_splice_write
Author: lizhi.xu@xxxxxxxxxxxxx

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 33e02dc69afb

diff --git a/fs/splice.c b/fs/splice.c
index 60aed8de21f8..abf45d6184a5 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -745,14 +745,25 @@ iter_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
 		if (ret <= 0)
 			break;
 
+		printk("ret: %zd, total len: %zu, %s\n", ret, sd.total_len, __func__);
+		if (ret > sd.total_len) {
+			ret = -EINVAL;
+			goto done;
+		}
 		sd.num_spliced += ret;
 		sd.total_len -= ret;
 		*ppos = sd.pos;
 
 		/* dismiss the fully eaten buffers, adjust the partial one */
 		tail = pipe->tail;
-		while (ret) {
+		n = 0;
+		while (ret > 0 && n < nbufs) {
 			struct pipe_buffer *buf = &pipe->bufs[tail & mask];
+			n++;
+			if (!buf->len) {
+				tail++;
+				continue;
+			}
 			if (ret >= buf->len) {
 				ret -= buf->len;
 				buf->len = 0;
diff --git a/fs/netfs/buffered_write.c b/fs/netfs/buffered_write.c
index 1121601536d1..f7c32835b094 100644
--- a/fs/netfs/buffered_write.c
+++ b/fs/netfs/buffered_write.c
@@ -510,6 +510,7 @@ ssize_t netfs_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
 	netfs_end_io_write(inode);
 	if (ret > 0)
 		ret = generic_write_sync(iocb, ret);
+	printk("ret: %ld, %s\n", ret, __func__);
 	return ret;
 }
 EXPORT_SYMBOL(netfs_file_write_iter);
diff --git a/fs/netfs/direct_write.c b/fs/netfs/direct_write.c
index 608ba6416919..ecd57c4d0ecb 100644
--- a/fs/netfs/direct_write.c
+++ b/fs/netfs/direct_write.c
@@ -69,6 +69,7 @@ static ssize_t netfs_unbuffered_write_iter_locked(struct kiocb *iocb, struct iov
 		 */
 		if (async || user_backed_iter(iter)) {
 			n = netfs_extract_user_iter(iter, len, &wreq->iter, 0);
+			printk("ret: %zd, %s\n", n, __func__);
 			if (n < 0) {
 				ret = n;
 				goto out;
@@ -190,6 +191,7 @@ ssize_t netfs_unbuffered_write_iter(struct kiocb *iocb, struct iov_iter *from)
 			   FSCACHE_INVAL_DIO_WRITE);
 	ret = netfs_unbuffered_write_iter_locked(iocb, from, NULL);
 out:
+	printk("ret: %zd, %s\n", ret, __func__);
 	netfs_end_io_direct(inode);
 	return ret;
 }