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* [Linux-kernel-mentees] [PATCH net] rds: Prevent kernel-infoleak in rds_notify_queue_get()
@ 2020-07-30 19:20 Peilin Ye
  2020-07-30 19:29 ` santosh.shilimkar
                   ` (2 more replies)
  0 siblings, 3 replies; 30+ messages in thread
From: Peilin Ye @ 2020-07-30 19:20 UTC (permalink / raw)
  To: Santosh Shilimkar
  Cc: Peilin Ye, David S. Miller, Jakub Kicinski, Dan Carpenter,
	Arnd Bergmann, Greg Kroah-Hartman, linux-kernel-mentees, netdev,
	linux-rdma, rds-devel, linux-kernel

rds_notify_queue_get() is potentially copying uninitialized kernel stack
memory to userspace since the compiler may leave a 4-byte hole at the end
of `cmsg`.

In 2016 we tried to fix this issue by doing `= { 0 };` on `cmsg`, which
unfortunately does not always initialize that 4-byte hole. Fix it by using
memset() instead.

Cc: stable@vger.kernel.org
Fixes: f037590fff30 ("rds: fix a leak of kernel memory")
Fixes: bdbe6fbc6a2f ("RDS: recv.c")
Suggested-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Peilin Ye <yepeilin.cs@gmail.com>
---
Note: the "real" copy_to_user() happens in put_cmsg(), where
`cmlen - sizeof(*cm)` equals to `sizeof(cmsg)`.

Reference: https://lwn.net/Articles/417989/

$ pahole -C "rds_rdma_notify" net/rds/recv.o
struct rds_rdma_notify {
	__u64                      user_token;           /*     0     8 */
	__s32                      status;               /*     8     4 */

	/* size: 16, cachelines: 1, members: 2 */
	/* padding: 4 */
	/* last cacheline: 16 bytes */
};

 net/rds/recv.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/rds/recv.c b/net/rds/recv.c
index c8404971d5ab..aba4afe4dfed 100644
--- a/net/rds/recv.c
+++ b/net/rds/recv.c
@@ -450,12 +450,13 @@ static int rds_still_queued(struct rds_sock *rs, struct rds_incoming *inc,
 int rds_notify_queue_get(struct rds_sock *rs, struct msghdr *msghdr)
 {
 	struct rds_notifier *notifier;
-	struct rds_rdma_notify cmsg = { 0 }; /* fill holes with zero */
+	struct rds_rdma_notify cmsg;
 	unsigned int count = 0, max_messages = ~0U;
 	unsigned long flags;
 	LIST_HEAD(copy);
 	int err = 0;
 
+	memset(&cmsg, 0, sizeof(cmsg));	/* fill holes with zero */
 
 	/* put_cmsg copies to user space and thus may sleep. We can't do this
 	 * with rs_lock held, so first grab as many notifications as we can stuff
-- 
2.25.1


^ permalink raw reply	[flat|nested] 30+ messages in thread

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Thread overview: 30+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-07-30 19:20 [Linux-kernel-mentees] [PATCH net] rds: Prevent kernel-infoleak in rds_notify_queue_get() Peilin Ye
2020-07-30 19:29 ` santosh.shilimkar
2020-07-31  4:53 ` Leon Romanovsky
2020-07-31  5:33   ` Greg Kroah-Hartman
2020-07-31  5:33     ` Greg Kroah-Hartman
     [not found]       ` <CAHp75Vdr2HC_ogNhBCxxGut9=Z6pQMFiA0w-268OQv+5unYOTg@mail.gmail.com>
2020-07-31  7:00         ` Leon Romanovsky
2020-07-31  7:05           ` Andy Shevchenko
2020-07-31 14:04       ` Jason Gunthorpe
2020-07-31 14:21         ` Greg Kroah-Hartman
2020-07-31 14:36           ` Jason Gunthorpe
2020-07-31 17:19             ` Greg Kroah-Hartman
2020-07-31 18:27               ` Jason Gunthorpe
2020-08-01  8:00                 ` Dan Carpenter
2020-08-01 14:40                   ` Jason Gunthorpe
2020-08-03  9:34                     ` Dan Carpenter
2020-08-01  5:38               ` Leon Romanovsky
2020-08-02 22:10                 ` Jason Gunthorpe
2020-08-02 22:23                   ` Joe Perches
2020-08-02 22:28                     ` Jason Gunthorpe
2020-08-02 22:45                       ` Joe Perches
2020-08-03  4:58                         ` Leon Romanovsky
2020-08-03 23:06                         ` Jason Gunthorpe
2020-08-08 22:57                           ` Jack Leadford
2020-08-09  7:04                             ` Leon Romanovsky
2020-08-14 17:07                             ` Jason Gunthorpe
2020-07-31  9:59   ` Dan Carpenter
2020-07-31 11:14     ` Håkon Bugge
2020-07-31 11:59       ` Greg Kroah-Hartman
2020-07-31 12:03         ` Håkon Bugge
2020-07-31 23:54 ` David Miller

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