linux-kernel - [PATCH V4] rxe: Fix a sleep-in-atomic bug in post_one

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Date:   Mon,  5 Jun 2017 17:39:48 +0800
From:   Jia-Ju Bai <baijiaju1990@....com>
To:     monis@...lanox.com, sean.hefty@...el.com, dledford@...hat.com,
        hal.rosenstock@...il.com, yuval.shaia@...cle.com
Cc:     linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jia-Ju Bai <baijiaju1990@....com>
Subject: [PATCH V4] rxe: Fix a sleep-in-atomic bug in post_one_send

The driver may sleep under a spin lock, and the function call path is:
post_one_send (acquire the lock by spin_lock_irqsave)
  init_send_wqe
    copy_from_user --> may sleep

There is no flow that makes "qp->is_user" true, and copy_from_user may 
cause bug when a non-user pointer is used. So, the line of copy_from_user
is removed.

Signed-off-by: Jia-Ju Bai <baijiaju1990@....com>
---
V4:
* Remove the line of copy_from_user.

V3:
* It corrects the mistakes of remaining legacy code in V2.
  (Thank Ram for pointing it out)

V2:
* The parameter "flags" is added to restore and save the irq status.
  Thank Leon for good advice.
---
 drivers/infiniband/sw/rxe/rxe_verbs.c |    6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/drivers/infiniband/sw/rxe/rxe_verbs.c b/drivers/infiniband/sw/rxe/rxe_verbs.c
index 83d709e..7c52c7c 100644
--- a/drivers/infiniband/sw/rxe/rxe_verbs.c
+++ b/drivers/infiniband/sw/rxe/rxe_verbs.c
@@ -740,11 +740,7 @@ static int init_send_wqe(struct rxe_qp *qp, struct ib_send_wr *ibwr,
 
 		sge = ibwr->sg_list;
 		for (i = 0; i < num_sge; i++, sge++) {
-			if (qp->is_user && copy_from_user(p, (__user void *)
-					    (uintptr_t)sge->addr, sge->length))
-				return -EFAULT;
-
-			else if (!qp->is_user)
+			if (!qp->is_user)
 				memcpy(p, (void *)(uintptr_t)sge->addr,
 				       sge->length);
 
-- 
1.7.9.5