Patch "seq_file: fix incomplete reset on read from zero offset" has been added to the 4.15-stable tree

Patch "seq_file: fix incomplete reset on read from zero offset" has been added to the 4.15-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    seq_file: fix incomplete reset on read from zero offset

to the 4.15-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     seq_file-fix-incomplete-reset-on-read-from-zero-offset.patch
and it can be found in the queue-4.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From cf5eebae2cd28d37581507668605f4d23cd7218d Mon Sep 17 00:00:00 2001
From: Miklos Szeredi <mszeredi@redhat.com>
Date: Wed, 15 Nov 2017 11:34:58 +0100
Subject: seq_file: fix incomplete reset on read from zero offset

From: Miklos Szeredi <mszeredi@redhat.com>

commit cf5eebae2cd28d37581507668605f4d23cd7218d upstream.

When resetting iterator on a zero offset we need to discard any data
already in the buffer (count), and private state of the iterator (version).

For example this bug results in first line being repeated in /proc/mounts
if doing a zero size read before a non-zero size read.

Reported-by: Rich Felker <dalias@libc.org>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Fixes: e522751d605d ("seq_file: reset iterator to first record for zero offset")
Cc: <stable@vger.kernel.org> # v4.10
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/seq_file.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

--- a/fs/seq_file.c
+++ b/fs/seq_file.c
@@ -181,8 +181,11 @@ ssize_t seq_read(struct file *file, char
 	 * if request is to read from zero offset, reset iterator to first
 	 * record as it might have been already advanced by previous requests
 	 */
-	if (*ppos == 0)
+	if (*ppos == 0) {
 		m->index = 0;
+		m->version = 0;
+		m->count = 0;
+	}
 
 	/* Don't assume *ppos is where we left it */
 	if (unlikely(*ppos != m->read_pos)) {


Patches currently in stable-queue which might be from mszeredi@redhat.com are

queue-4.15/seq_file-fix-incomplete-reset-on-read-from-zero-offset.patch