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Date: Thu, 23 May 2024 18:30:00 -0700
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Subject: Re: [syzbot] [syzbot] [fs?] general protection fault in iter_file_splice_write
From: syzbot <syzbot+d2125fcb6aa8c4276fd2@syzkaller.appspotmail.com>
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Subject: [syzbot] [fs?] general protection fault in iter_file_splice_write
Author: lizhi.xu@windriver.com

#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..c6d812684d4e 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -745,16 +745,30 @@ iter_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
 		if (ret <= 0)
 			break;
 
+		printk("ret: %ld, total len: %lu, %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];
+			printk("ret: %ld, nbufs: %d, buf:%p, buf len: %u, m: %u, t: %u,ring size: %u, t&m: %u, n:%d, %s\n", 
+					ret, nbufs, buf, buf->len, mask, tail, pipe->ring_size, tail & mask, n, __func__);
+			n++;
+			if (!buf->len) {
+				tail++;
+				continue;
+			}
 			if (ret >= buf->len) {
 				ret -= buf->len;
+				printk("ret: %ld, %s\n", ret, __func__);
 				buf->len = 0;
 				pipe_buf_release(pipe, buf);
 				tail++;
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..8157b4e6d7b3 100644
--- a/fs/netfs/direct_write.c
+++ b/fs/netfs/direct_write.c
@@ -190,6 +190,7 @@ 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: %ld, %s\n", ret, __func__);
 	netfs_end_io_direct(inode);
 	return ret;
 }