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[4.2.y-ckt,stable] Patch "direct-io: Fix negative return from dio read beyond eof" has been added to staging queue

Message ID 1452882592-16783-1-git-send-email-kamal@canonical.com
State New
Headers show

Commit Message

Kamal Mostafa Jan. 15, 2016, 6:29 p.m. UTC 
This is a note to let you know that I have just added a patch titled

    direct-io: Fix negative return from dio read beyond eof

to the linux-4.2.y-queue branch of the 4.2.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-4.2.y-queue

This patch is scheduled to be released in version 4.2.8-ckt2.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 4.2.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

---8<------------------------------------------------------------

From b0c8b60d785d1248a8b5fbb760bbe96afabd8b9b Mon Sep 17 00:00:00 2001
From: Jan Kara <jack@suse.cz>
Date: Mon, 30 Nov 2015 10:15:42 -0700
Subject: direct-io: Fix negative return from dio read beyond eof

commit 74cedf9b6c603f2278a05bc91b140b32b434d0b5 upstream.

Assume a filesystem with 4KB blocks. When a file has size 1000 bytes and
we issue direct IO read at offset 1024, blockdev_direct_IO() reads the
tail of the last block and the logic for handling short DIO reads in
dio_complete() results in a return value -24 (1000 - 1024) which
obviously confuses userspace.

Fix the problem by bailing out early once we sample i_size and can
reliably check that direct IO read starts beyond i_size.

Reported-by: Avi Kivity <avi@scylladb.com>
Fixes: 9fe55eea7e4b444bafc42fa0000cc2d1d2847275
CC: Steven Whitehouse <swhiteho@redhat.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Jens Axboe <axboe@fb.com>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
---
 fs/direct-io.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

--
1.9.1
diff mbox

Patch

diff --git a/fs/direct-io.c b/fs/direct-io.c
index 745d234..6bc4bac 100644
--- a/fs/direct-io.c
+++ b/fs/direct-io.c
@@ -1159,6 +1159,15 @@  do_blockdev_direct_IO(struct kiocb *iocb, struct inode *inode,
 		}
 	}

+	/* Once we sampled i_size check for reads beyond EOF */
+	dio->i_size = i_size_read(inode);
+	if (iov_iter_rw(iter) == READ && offset >= dio->i_size) {
+		if (dio->flags & DIO_LOCKING)
+			mutex_unlock(&inode->i_mutex);
+		kmem_cache_free(dio_cache, dio);
+		goto out;
+	}
+
 	/*
 	 * For file extending writes updating i_size before data writeouts
 	 * complete can expose uninitialized blocks in dumb filesystems.
@@ -1212,7 +1221,6 @@  do_blockdev_direct_IO(struct kiocb *iocb, struct inode *inode,
 	sdio.next_block_for_io = -1;

 	dio->iocb = iocb;
-	dio->i_size = i_size_read(inode);

 	spin_lock_init(&dio->bio_lock);
 	dio->refcount = 1;