6.6-stable review patch. If anyone has any objections, please let me know.
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From: Jinhui Guo guojinhui.liam@bytedance.com
[ Upstream commit 936750fdba4c45e13bbd17f261bb140dd55f5e93 ]
The race window between __scan_channels() and deliver_response() causes the parameters of some channels to be set to 0.
1.[CPUA] __scan_channels() issues an IPMI request and waits with wait_event() until all channels have been scanned. wait_event() internally calls might_sleep(), which might yield the CPU. (Moreover, an interrupt can preempt wait_event() and force the task to yield the CPU.) 2.[CPUB] deliver_response() is invoked when the CPU receives the IPMI response. After processing a IPMI response, deliver_response() directly assigns intf->wchannels to intf->channel_list and sets intf->channels_ready to true. However, not all channels are actually ready for use. 3.[CPUA] Since intf->channels_ready is already true, wait_event() never enters __wait_event(). __scan_channels() immediately clears intf->null_user_handler and exits. 4.[CPUB] Once intf->null_user_handler is set to NULL, deliver_response() ignores further IPMI responses, leaving the remaining channels zero-initialized and unusable.
CPUA CPUB ------------------------------- ----------------------------- __scan_channels() intf->null_user_handler = channel_handler; send_channel_info_cmd(intf, 0); wait_event(intf->waitq, intf->channels_ready); do { might_sleep(); deliver_response() channel_handler() intf->channel_list = intf->wchannels + set; intf->channels_ready = true; send_channel_info_cmd(intf, intf->curr_channel); if (condition) break; __wait_event(wq_head, condition); } while(0) intf->null_user_handler = NULL; deliver_response() if (!msg->user) if (intf->null_user_handler) rv = -EINVAL; return rv; ------------------------------- -----------------------------
Fix the race between __scan_channels() and deliver_response() by deferring both the assignment intf->channel_list = intf->wchannels and the flag intf->channels_ready = true until all channels have been successfully scanned or until the IPMI request has failed.
Signed-off-by: Jinhui Guo guojinhui.liam@bytedance.com Message-ID: 20250930074239.2353-2-guojinhui.liam@bytedance.com Signed-off-by: Corey Minyard corey@minyard.net Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/char/ipmi/ipmi_msghandler.c | 2 -- 1 file changed, 2 deletions(-)
diff --git a/drivers/char/ipmi/ipmi_msghandler.c b/drivers/char/ipmi/ipmi_msghandler.c index b7d8bf202ed2..4619ee5c744c 100644 --- a/drivers/char/ipmi/ipmi_msghandler.c +++ b/drivers/char/ipmi/ipmi_msghandler.c @@ -3414,8 +3414,6 @@ channel_handler(struct ipmi_smi *intf, struct ipmi_recv_msg *msg) intf->channels_ready = true; wake_up(&intf->waitq); } else { - intf->channel_list = intf->wchannels + set; - intf->channels_ready = true; rv = send_channel_info_cmd(intf, intf->curr_channel); }