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

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Message-ID: <tencent_7BA1330A9E431B2B4B071B6B2518BA37BB08@qq.com>
Date: Wed, 22 May 2024 19:30:37 +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..db66b8c5fe0d 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -751,21 +751,25 @@ 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) {
+		printk("ret: %ld, %s\n", ret, __func__);
+		while (ret > 0) {
 			struct pipe_buffer *buf = &pipe->bufs[tail & mask];
-			if (ret >= buf->len) {
-				ret -= buf->len;
-				buf->len = 0;
-				pipe_buf_release(pipe, buf);
-				tail++;
-				pipe->tail = tail;
-				if (pipe->files)
-					sd.need_wakeup = true;
-			} else {
-				buf->offset += ret;
-				buf->len -= ret;
+			if (buf->len > 0) {
+				if (ret >= (ssize_t)buf->len) {
+					ret -= buf->len;
+					buf->len = 0;
+					pipe_buf_release(pipe, buf);
+					tail++;
+					pipe->tail = tail;
+					if (pipe->files)
+						sd.need_wakeup = true;
+				} else {
+					buf->offset += ret;
+					buf->len -= ret;
+					ret = 0;
+				}
+			} else
 				ret = 0;
-			}
 		}
 	}
 done: