linux-kernel - Re: [syzbot] [fs?] general protection fault in iter_file_splice

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Date: Thu, 23 May 2024 22:13:00 +0800
From: Edward Adam Davis <eadavis@...com>
To: syzbot+d2125fcb6aa8c4276fd2@...kaller.appspotmail.com
Cc: linux-kernel@...r.kernel.org,
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [fs?] general protection fault in iter_file_splice_write

please test null ptr in iter_file_splice_write

#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..2881e9a7e491 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -751,10 +751,19 @@ iter_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
 
 		/* 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) {
+				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__);
 				ret -= buf->len;
+				printk("ret: %ld, %s\n", ret, __func__);
 				buf->len = 0;
 				pipe_buf_release(pipe, buf);
 				tail++;