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can: bcm: add missing rcu read protection for procfs content

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commit dac5e6249159ac255dad9781793dbe5908ac9ddb upstream.

When the procfs content is generated for a bcm_op which is in the process
to be removed the procfs output might show unreliable data (UAF).

As the removal of bcm_op's is already implemented with rcu handling this
patch adds the missing rcu_read_lock() and makes sure the list entries
are properly removed under rcu protection.

Fixes: f1b4e32aca08 ("can: bcm: use call_rcu() instead of costly synchronize_rcu()")
Reported-by: Anderson Nascimento <anderson@allelesecurity.com>
Suggested-by: Anderson Nascimento <anderson@allelesecurity.com>
Tested-by: Anderson Nascimento <anderson@allelesecurity.com>
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
Link: https://patch.msgid.link/20250519125027.11900-2-socketcan@hartkopp.net
Cc: stable@vger.kernel.org # >= 5.4
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Oliver Hartkopp 2025-05-19 14:50:27 +02:00 • committed by Greg Kroah-Hartman
commit 19f553a1dd
1 changed files with 9 additions and 4 deletions
Download patch file Download diff file Expand all files Collapse all files

13
net/can/bcm.c
View file

@ -209,7 +209,9 @@ static int bcm_proc_show(struct seq_file *m, void *v)
seq_printf(m, " / bound %s", bcm_proc_getifname(net, ifname, bo->ifindex));
seq_printf(m, " <<<\n");
list_for_each_entry(op, &bo->rx_ops, list) {
rcu_read_lock();
list_for_each_entry_rcu(op, &bo->rx_ops, list) {
unsigned long reduction;
@ -265,6 +267,9 @@ static int bcm_proc_show(struct seq_file *m, void *v)
seq_printf(m, "# sent %ld\n", op->frames_abs);
}
seq_putc(m, '\n');
rcu_read_unlock();
return 0;
}
#endif /* CONFIG_PROC_FS */
@ -813,7 +818,7 @@ static int bcm_delete_rx_op(struct list_head *ops, struct bcm_msg_head *mh,
REGMASK(op->can_id),
bcm_rx_handler, op);
list_del(&op->list);
list_del_rcu(&op->list);
bcm_remove_op(op);
return 1; /* done */
}
@ -833,7 +838,7 @@ static int bcm_delete_tx_op(struct list_head *ops, struct bcm_msg_head *mh,
list_for_each_entry_safe(op, n, ops, list) {
if ((op->can_id == mh->can_id) && (op->ifindex == ifindex) &&
(op->flags & CAN_FD_FRAME) == (mh->flags & CAN_FD_FRAME)) {
list_del(&op->list);
list_del_rcu(&op->list);
bcm_remove_op(op);
return 1; /* done */
}
@ -1255,7 +1260,7 @@ static int bcm_rx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
bcm_rx_handler, op, "bcm", sk);
if (err) {
/* this bcm rx op is broken -> remove it */
list_del(&op->list);
list_del_rcu(&op->list);
bcm_remove_op(op);
return err;
}