linux-kernel - [PATCH AUTOSEL 5.7 57/61] ceph: do not access the kiocb after aio requests

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Date:   Fri, 21 Aug 2020 12:15:41 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Xiubo Li <xiubli@...hat.com>, Jeff Layton <jlayton@...nel.org>,
        Ilya Dryomov <idryomov@...il.com>,
        Sasha Levin <sashal@...nel.org>, ceph-devel@...r.kernel.org
Subject: [PATCH AUTOSEL 5.7 57/61] ceph: do not access the kiocb after aio requests

From: Xiubo Li <xiubli@...hat.com>

[ Upstream commit d1d9655052606fd9078e896668ec90191372d513 ]

In aio case, if the completion comes very fast just before the
ceph_read_iter() returns to fs/aio.c, the kiocb will be freed in
the completion callback, then if ceph_read_iter() access again
we will potentially hit the use-after-free bug.

[ jlayton: initialize direct_lock early, and use it everywhere ]

URL: https://tracker.ceph.com/issues/45649
Signed-off-by: Xiubo Li <xiubli@...hat.com>
Signed-off-by: Jeff Layton <jlayton@...nel.org>
Signed-off-by: Ilya Dryomov <idryomov@...il.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 fs/ceph/file.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/fs/ceph/file.c b/fs/ceph/file.c
index afdfca965a7fc..599eca249973d 100644
--- a/fs/ceph/file.c
+++ b/fs/ceph/file.c
@@ -1508,6 +1508,7 @@ static ssize_t ceph_read_iter(struct kiocb *iocb, struct iov_iter *to)
 	struct inode *inode = file_inode(filp);
 	struct ceph_inode_info *ci = ceph_inode(inode);
 	struct page *pinned_page = NULL;
+	bool direct_lock = iocb->ki_flags & IOCB_DIRECT;
 	ssize_t ret;
 	int want, got = 0;
 	int retry_op = 0, read = 0;
@@ -1516,7 +1517,7 @@ static ssize_t ceph_read_iter(struct kiocb *iocb, struct iov_iter *to)
 	dout("aio_read %p %llx.%llx %llu~%u trying to get caps on %p\n",
 	     inode, ceph_vinop(inode), iocb->ki_pos, (unsigned)len, inode);
 
-	if (iocb->ki_flags & IOCB_DIRECT)
+	if (direct_lock)
 		ceph_start_io_direct(inode);
 	else
 		ceph_start_io_read(inode);
@@ -1573,7 +1574,7 @@ static ssize_t ceph_read_iter(struct kiocb *iocb, struct iov_iter *to)
 	}
 	ceph_put_cap_refs(ci, got);
 
-	if (iocb->ki_flags & IOCB_DIRECT)
+	if (direct_lock)
 		ceph_end_io_direct(inode);
 	else
 		ceph_end_io_read(inode);
-- 
2.25.1