6.6-stable review patch. If anyone has any objections, please let me know.
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From: Oliver Hartkopp socketcan@hartkopp.net
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 --- net/can/bcm.c | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-)
--- a/net/can/bcm.c +++ b/net/can/bcm.c @@ -207,7 +207,9 @@ static int bcm_proc_show(struct seq_file 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;
@@ -263,6 +265,9 @@ static int bcm_proc_show(struct seq_file seq_printf(m, "# sent %ld\n", op->frames_abs); } seq_putc(m, '\n'); + + rcu_read_unlock(); + return 0; } #endif /* CONFIG_PROC_FS */ @@ -816,7 +821,7 @@ static int bcm_delete_rx_op(struct list_ REGMASK(op->can_id), bcm_rx_handler, op);
- list_del(&op->list); + list_del_rcu(&op->list); bcm_remove_op(op); return 1; /* done */ } @@ -836,7 +841,7 @@ static int bcm_delete_tx_op(struct list_ 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 */ } @@ -1258,7 +1263,7 @@ static int bcm_rx_setup(struct bcm_msg_h 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; }