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

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 <[email protected]> know about it.

From: Linus Torvalds <[email protected]>
Date: Wed, 14 Dec 2016 12:45:25 -0800
Subject: vfs,mm: fix return value of read() at s_maxbytes

From: Linus Torvalds <[email protected]>

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.

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

@@ -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 [email protected] 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