From 05ec76cfbce653e07cec19b9b8b20e33449d5d87 Mon Sep 17 00:00:00 2001 From: Yifei Gao Date: Tue, 25 Aug 2026 23:46:29 +0000 Subject: ipmi: Fix use-after-free of cmd_rcvr in _ipmi_destroy_user() Commit 9e91f8a6c868 ("ipmi:msghandler: Remove srcu for the ipmi_interfaces list") dropped the synchronize_rcu() between unlinking the command receivers from intf->cmd_rcvrs and freeing them, updating only the comment that explains why the barrier is needed. The cmd_rcvrs list is still traversed under plain RCU: find_cmd_rcvr() walks it inside rcu_read_lock(), and handle_ipmb_get_msg_cmd() borrows rcvr->user from that lookup within the same read-side section. Without the grace period, _ipmi_destroy_user() can kfree() a cmd_rcvr while a reader still holds a pointer to it, causing a use-after-free. The rework only made srcu unnecessary for the interfaces list; the cmd_rcvrs list still relies on plain RCU. Restore the synchronize_rcu() before freeing the receivers. Fixes: 9e91f8a6c868 ("ipmi:msghandler: Remove srcu for the ipmi_interfaces list") Cc: stable@vger.kernel.org Assisted-by: Claude:claude-opus-4-8 Signed-off-by: Yifei Gao Message-ID: <20260825234630.1196170-1-gyf161023@gmail.com> Signed-off-by: Corey Minyard --- drivers/char/ipmi/ipmi_msghandler.c | 1 + 1 file changed, 1 insertion(+) diff --git a/drivers/char/ipmi/ipmi_msghandler.c b/drivers/char/ipmi/ipmi_msghandler.c index c73e9def59a6..152dd6b5bb27 100644 --- a/drivers/char/ipmi/ipmi_msghandler.c +++ b/drivers/char/ipmi/ipmi_msghandler.c @@ -1391,6 +1391,7 @@ static void _ipmi_destroy_user(struct ipmi_user *user) } } mutex_unlock(&intf->cmd_rcvrs_mutex); + synchronize_rcu(); while (rcvrs) { rcvr = rcvrs; rcvrs = rcvr->next; -- cgit v1.2.3