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[PATCH V2] rxe: Fix a sleep-in-atomic bug in post_one_send

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  [PATCH V2] rxe: Fix a sleep-in-atomic bug in post_one_send Jia-Ju Bai <baijiaju1990@163.com> - 2017-06-01 09:50 +0200
    RE: [PATCH V2] rxe: Fix a sleep-in-atomic bug in post_one_send "Amrani, Ram" <Ram.Amrani@cavium.com> - 2017-06-01 10:20 +0200

#1654893 — [PATCH V2] 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

To fix it, the lock is released before copy_from_user, and the lock is
acquired again after this function. The parameter "flags" is used to
restore and save the irq status.
Thank Leon for good advice.

Signed-off-by: Jia-Ju Bai <baijiaju1990@163.com>
---
 drivers/infiniband/sw/rxe/rxe_verbs.c |   13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/drivers/infiniband/sw/rxe/rxe_verbs.c b/drivers/infiniband/sw/rxe/rxe_verbs.c
index 83d709e..7dcdf67 100644
--- a/drivers/infiniband/sw/rxe/rxe_verbs.c
+++ b/drivers/infiniband/sw/rxe/rxe_verbs.c
@@ -721,11 +721,11 @@ static void init_send_wr(struct rxe_qp *qp, struct rxe_send_wr *wr,
 
 static int init_send_wqe(struct rxe_qp *qp, struct ib_send_wr *ibwr,
 			 unsigned int mask, unsigned int length,
-			 struct rxe_send_wqe *wqe)
+			 struct rxe_send_wqe *wqe, unsigned long *flags)
 {
 	int num_sge = ibwr->num_sge;
 	struct ib_sge *sge;
-	int i;
+	int i, err;
 	u8 *p;
 
 	init_send_wr(qp, &wqe->wr, ibwr);
@@ -742,7 +742,12 @@ static int init_send_wqe(struct rxe_qp *qp, struct ib_send_wr *ibwr,
 		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;
+				spin_unlock_irqrestore(&qp->sq.sq_lock, *flags);
+				err = copy_from_user(p, (__user void *)
+					    (uintptr_t)sge->addr, sge->length);
+				spin_lock_irqsave(&qp->sq.sq_lock, *flags);
+				if (qp->is_user && err)
+					return -EFAULT;
 
 			else if (!qp->is_user)
 				memcpy(p, (void *)(uintptr_t)sge->addr,
@@ -794,7 +799,7 @@ static int post_one_send(struct rxe_qp *qp, struct ib_send_wr *ibwr,
 
 	send_wqe = producer_addr(sq->queue);
 
-	err = init_send_wqe(qp, ibwr, mask, length, send_wqe);
+	err = init_send_wqe(qp, ibwr, mask, length, send_wqe, &flags);
 	if (unlikely(err))
 		goto err1;
 
-- 
1.7.9.5

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#1654908

> 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
> 
> To fix it, the lock is released before copy_from_user, and the lock is
> acquired again after this function. The parameter "flags" is used to
> restore and save the irq status.
> Thank Leon for good advice.
> 

...

>  	init_send_wr(qp, &wqe->wr, ibwr);
> @@ -742,7 +742,12 @@ static int init_send_wqe(struct rxe_qp *qp, struct ib_send_wr *ibwr,
>  		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;
> +				spin_unlock_irqrestore(&qp->sq.sq_lock, *flags);
> +				err = copy_from_user(p, (__user void *)
> +					    (uintptr_t)sge->addr, sge->length);
> +				spin_lock_irqsave(&qp->sq.sq_lock, *flags);
> +				if (qp->is_user && err)
> +					return -EFAULT;
> 
>  			else if (!qp->is_user)
>  				memcpy(p, (void *)(uintptr_t)sge->addr,

This isn't my area of expertise. Still something seems weird.
You are still calling 'copy_from_user' unprotected in the 'if'.
Also, did you mean to use curly brackets on the indented part after the first if?!

Ram

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