linux-kernel - [PATCH 4.19 239/243] iomap: Fix pipe page leakage during splicing

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20191211150355.471454825@linuxfoundation.org>
Date:   Wed, 11 Dec 2019 16:06:41 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        syzbot+991400e8eba7e00a26e1@...kaller.appspotmail.com,
        Jan Kara <jack@...e.cz>,
        "Darrick J. Wong" <darrick.wong@...cle.com>,
        Christoph Hellwig <hch@....de>
Subject: [PATCH 4.19 239/243] iomap: Fix pipe page leakage during splicing

From: Jan Kara <jack@...e.cz>

commit 419e9c38aa075ed0cd3c13d47e15954b686bcdb6 upstream.

When splicing using iomap_dio_rw() to a pipe, we may leak pipe pages
because bio_iov_iter_get_pages() records that the pipe will have full
extent worth of data however if file size is not block size aligned
iomap_dio_rw() returns less than what bio_iov_iter_get_pages() set up
and splice code gets confused leaking a pipe page with the file tail.

Handle the situation similarly to the old direct IO implementation and
revert iter to actually returned read amount which makes iter consistent
with value returned from iomap_dio_rw() and thus the splice code is
happy.

Fixes: ff6a9292e6f6 ("iomap: implement direct I/O")
CC: stable@...r.kernel.org
Reported-by: syzbot+991400e8eba7e00a26e1@...kaller.appspotmail.com
Signed-off-by: Jan Kara <jack@...e.cz>
Reviewed-by: Darrick J. Wong <darrick.wong@...cle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@...cle.com>
Reviewed-by: Christoph Hellwig <hch@....de>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/iomap.c |    9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

--- a/fs/iomap.c
+++ b/fs/iomap.c
@@ -1913,8 +1913,15 @@ iomap_dio_rw(struct kiocb *iocb, struct
 		}
 		pos += ret;

-		if (iov_iter_rw(iter) == READ && pos >= dio->i_size)
+		if (iov_iter_rw(iter) == READ && pos >= dio->i_size) {
+			/*
+			 * We only report that we've read data up to i_size.
+			 * Revert iter to a state corresponding to that as
+			 * some callers (such as splice code) rely on it.
+			 */
+			iov_iter_revert(iter, pos - dio->i_size);
 			break;
+		}
 	} while ((count = iov_iter_count(iter)) > 0);
 	blk_finish_plug(&plug);