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rds: Prevent kernel-infoleak in rds_notify_queue_get()

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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: f037590fff ("rds: fix a leak of kernel memory")
Fixes: bdbe6fbc6a ("RDS: recv.c")
Suggested-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Peilin Ye <yepeilin.cs@gmail.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Peilin Ye 2020-07-30 15:20:26 -04:00 committed by David S. Miller
parent dc096288d5
commit bbc8a99e95
1 changed files with 2 additions and 1 deletions
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3
net/rds/recv.c
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@ -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) int rds_notify_queue_get(struct rds_sock *rs, struct msghdr *msghdr)
{ {
struct rds_notifier *notifier; 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 int count = 0, max_messages = ~0U;
unsigned long flags; unsigned long flags;
LIST_HEAD(copy); LIST_HEAD(copy);
int err = 0; 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 /* 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 * with rs_lock held, so first grab as many notifications as we can stuff