Patch "vfs,mm: fix return value of read() at s_maxbytes" has been added to the 4.9-stable tree

[<gregkh@linuxfoundation.org>]

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

    vfs,mm: fix return value of read() at s_maxbytes

to the 4.9-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:
     vfs-mm-fix-return-value-of-read-at-s_maxbytes.patch
and it can be found in the queue-4.9 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 d05c5f7ba164aed3db02fb188c26d0dd94f5455b Mon Sep 17 00:00:00 2001
From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Wed, 14 Dec 2016 12:45:25 -0800
Subject: vfs,mm: fix return value of read() at s_maxbytes

From: Linus Torvalds <torvalds@linux-foundation.org>

commit d05c5f7ba164aed3db02fb188c26d0dd94f5455b upstream.

We truncated the possible read iterator to s_maxbytes in commit
c2a9737f45e2 ("vfs,mm: fix a dead loop in truncate_inode_pages_range()"),
but our end condition handling was wrong: it's not an error to try to
read at the end of the file.

Reading past the end should return EOF (0), not EINVAL.

See for example

  https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1649342
  http://lists.gnu.org/archive/html/bug-coreutils/2016-12/msg00008.html

where a md5sum of a maximally sized file fails because the final read is
exactly at s_maxbytes.

Fixes: c2a9737f45e2 ("vfs,mm: fix a dead loop in truncate_inode_pages_range()")
Reported-by: Joseph Salisbury <joseph.salisbury@canonical.com>
Cc: Wei Fang <fangwei1@huawei.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 mm/filemap.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1686,7 +1686,7 @@ static ssize_t do_generic_file_read(stru
 	int error = 0;
 
 	if (unlikely(*ppos >= inode->i_sb->s_maxbytes))
-		return -EINVAL;
+		return 0;
 	iov_iter_truncate(iter, inode->i_sb->s_maxbytes);
 
 	index = *ppos >> PAGE_SHIFT;


Patches currently in stable-queue which might be from torvalds@linux-foundation.org are

queue-4.9/mm-page_alloc-keep-pcp-count-and-list-contents-in-sync-if-struct-page-is-corrupted.patch
queue-4.9/splice-reinstate-sigpipe-epipe-handling.patch
queue-4.9/mm-vmscan.c-set-correct-defer-count-for-shrinker.patch
queue-4.9/vfs-mm-fix-return-value-of-read-at-s_maxbytes.patch