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[128.210.106.74]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-3283d60bf36sm2764869eec.2.2026.08.25.16.46.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 25 Aug 2026 16:46:41 -0700 (PDT) From: Yifei Gao To: corey@minyard.net Cc: openipmi-developer@lists.sourceforge.net, linux-kernel@vger.kernel.org, stable@vger.kernel.org, Yifei Gao Subject: [PATCH] ipmi: Fix use-after-free of cmd_rcvr in _ipmi_destroy_user() Date: Tue, 25 Aug 2026 23:46:29 +0000 Message-ID: <20260825234630.1196170-1-gyf161023@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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 --- 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 ab4c85f3d6fe..3f4018194df8 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; -- 2.43.0