6.12-stable review patch. If anyone has any objections, please let me know.
------------------
From: Oliver Hartkopp socketcan@hartkopp.net
commit c2aba69d0c36a496ab4f2e81e9c2b271f2693fd7 upstream.
The CAN broadcast manager (CAN BCM) can send a sequence of CAN frames via hrtimer. The content and also the length of the sequence can be changed resp reduced at runtime where the 'currframe' counter is then set to zero.
Although this appeared to be a safe operation the updates of 'currframe' can be triggered from user space and hrtimer context in bcm_can_tx(). Anderson Nascimento created a proof of concept that triggered a KASAN slab-out-of-bounds read access which can be prevented with a spin_lock_bh.
At the rework of bcm_can_tx() the 'count' variable has been moved into the protected section as this variable can be modified from both contexts too.
Fixes: ffd980f976e7 ("[CAN]: Add broadcast manager (bcm) protocol") Reported-by: Anderson Nascimento anderson@allelesecurity.com Tested-by: Anderson Nascimento anderson@allelesecurity.com Reviewed-by: Marc Kleine-Budde mkl@pengutronix.de Signed-off-by: Oliver Hartkopp socketcan@hartkopp.net Link: https://patch.msgid.link/20250519125027.11900-1-socketcan@hartkopp.net Cc: stable@vger.kernel.org Signed-off-by: Marc Kleine-Budde mkl@pengutronix.de Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/can/bcm.c | 66 +++++++++++++++++++++++++++++++++++++++------------------- 1 file changed, 45 insertions(+), 21 deletions(-)
--- a/net/can/bcm.c +++ b/net/can/bcm.c @@ -58,6 +58,7 @@ #include <linux/can/skb.h> #include <linux/can/bcm.h> #include <linux/slab.h> +#include <linux/spinlock.h> #include <net/sock.h> #include <net/net_namespace.h>
@@ -122,6 +123,7 @@ struct bcm_op { struct canfd_frame last_sframe; struct sock *sk; struct net_device *rx_reg_dev; + spinlock_t bcm_tx_lock; /* protect currframe/count in runtime updates */ };
struct bcm_sock { @@ -285,13 +287,18 @@ static void bcm_can_tx(struct bcm_op *op { struct sk_buff *skb; struct net_device *dev; - struct canfd_frame *cf = op->frames + op->cfsiz * op->currframe; + struct canfd_frame *cf; int err;
/* no target device? => exit */ if (!op->ifindex) return;
+ /* read currframe under lock protection */ + spin_lock_bh(&op->bcm_tx_lock); + cf = op->frames + op->cfsiz * op->currframe; + spin_unlock_bh(&op->bcm_tx_lock); + dev = dev_get_by_index(sock_net(op->sk), op->ifindex); if (!dev) { /* RFC: should this bcm_op remove itself here? */ @@ -312,6 +319,10 @@ static void bcm_can_tx(struct bcm_op *op skb->dev = dev; can_skb_set_owner(skb, op->sk); err = can_send(skb, 1); + + /* update currframe and count under lock protection */ + spin_lock_bh(&op->bcm_tx_lock); + if (!err) op->frames_abs++;
@@ -320,6 +331,11 @@ static void bcm_can_tx(struct bcm_op *op /* reached last frame? */ if (op->currframe >= op->nframes) op->currframe = 0; + + if (op->count > 0) + op->count--; + + spin_unlock_bh(&op->bcm_tx_lock); out: dev_put(dev); } @@ -430,7 +446,7 @@ static enum hrtimer_restart bcm_tx_timeo struct bcm_msg_head msg_head;
if (op->kt_ival1 && (op->count > 0)) { - op->count--; + bcm_can_tx(op); if (!op->count && (op->flags & TX_COUNTEVT)) {
/* create notification to user */ @@ -445,7 +461,6 @@ static enum hrtimer_restart bcm_tx_timeo
bcm_send_to_user(op, &msg_head, NULL, 0); } - bcm_can_tx(op);
} else if (op->kt_ival2) { bcm_can_tx(op); @@ -956,6 +971,27 @@ static int bcm_tx_setup(struct bcm_msg_h } op->flags = msg_head->flags;
+ /* only lock for unlikely count/nframes/currframe changes */ + if (op->nframes != msg_head->nframes || + op->flags & TX_RESET_MULTI_IDX || + op->flags & SETTIMER) { + + spin_lock_bh(&op->bcm_tx_lock); + + if (op->nframes != msg_head->nframes || + op->flags & TX_RESET_MULTI_IDX) { + /* potentially update changed nframes */ + op->nframes = msg_head->nframes; + /* restart multiple frame transmission */ + op->currframe = 0; + } + + if (op->flags & SETTIMER) + op->count = msg_head->count; + + spin_unlock_bh(&op->bcm_tx_lock); + } + } else { /* insert new BCM operation for the given can_id */
@@ -963,9 +999,14 @@ static int bcm_tx_setup(struct bcm_msg_h if (!op) return -ENOMEM;
+ spin_lock_init(&op->bcm_tx_lock); op->can_id = msg_head->can_id; op->cfsiz = CFSIZ(msg_head->flags); op->flags = msg_head->flags; + op->nframes = msg_head->nframes; + + if (op->flags & SETTIMER) + op->count = msg_head->count;
/* create array for CAN frames and copy the data */ if (msg_head->nframes > 1) { @@ -1024,22 +1065,8 @@ static int bcm_tx_setup(struct bcm_msg_h
} /* if ((op = bcm_find_op(&bo->tx_ops, msg_head->can_id, ifindex))) */
- if (op->nframes != msg_head->nframes) { - op->nframes = msg_head->nframes; - /* start multiple frame transmission with index 0 */ - op->currframe = 0; - } - - /* check flags */ - - if (op->flags & TX_RESET_MULTI_IDX) { - /* start multiple frame transmission with index 0 */ - op->currframe = 0; - } - if (op->flags & SETTIMER) { /* set timer values */ - op->count = msg_head->count; op->ival1 = msg_head->ival1; op->ival2 = msg_head->ival2; op->kt_ival1 = bcm_timeval_to_ktime(msg_head->ival1); @@ -1056,11 +1083,8 @@ static int bcm_tx_setup(struct bcm_msg_h op->flags |= TX_ANNOUNCE; }
- if (op->flags & TX_ANNOUNCE) { + if (op->flags & TX_ANNOUNCE) bcm_can_tx(op); - if (op->count) - op->count--; - }
if (op->flags & STARTTIMER) bcm_tx_start_timer(op);