From e2bda39d7f9f285ec803e200b5c1f17143d0b483 Mon Sep 17 00:00:00 2001 From: Maoyi Xie Date: Wed, 24 Jun 2026 13:04:33 +0800 Subject: [PATCH] i3c: master: svc: bound IBI payload to the requested max_payload_len svc_i3c_master_handle_ibi() reads the IBI payload from the RX FIFO into the IBI slot. The loop is bounded by the hardware FIFO size (SVC_I3C_FIFO_SIZE), not by the slot size. slot->data points into the IBI pool, which i3c_generic_ibi_alloc_pool() sizes at max_payload_len per slot. svc_i3c_master_request_ibi() only rejects a max_payload_len larger than SVC_I3C_FIFO_SIZE, so a driver can request a smaller one. mctp-i3c requests 1. Each readsb() then copies the controller RXCOUNT bytes (up to 31) with no check against the slot size. A device that sends more bytes than the slot holds writes past slot->data, an out-of-bounds write into the IBI pool. Bound the loop by dev->ibi->max_payload_len and clamp each read to the space left in the slot, the same way dw-i3c does. A device can still send more than the requested payload. Flush the leftover bytes from the RX FIFO so they do not leak into the next transfer. Fixes: dd3c52846d59 ("i3c: master: svc: Add Silvaco I3C master driver") Cc: stable@vger.kernel.org Co-developed-by: Kaixuan Li Signed-off-by: Kaixuan Li Signed-off-by: Maoyi Xie Reviewed-by: Frank Li Link: https://patch.msgid.link/178227747353.2931373.15868718612134648277@maoyixie.com Signed-off-by: Alexandre Belloni --- drivers/i3c/master/svc-i3c-master.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/drivers/i3c/master/svc-i3c-master.c b/drivers/i3c/master/svc-i3c-master.c index ae38ceee5abf..486c22840ea9 100644 --- a/drivers/i3c/master/svc-i3c-master.c +++ b/drivers/i3c/master/svc-i3c-master.c @@ -455,14 +455,22 @@ static int svc_i3c_master_handle_ibi(struct svc_i3c_master *master, buf = slot->data; while (SVC_I3C_MSTATUS_RXPEND(readl(master->regs + SVC_I3C_MSTATUS)) && - slot->len < SVC_I3C_FIFO_SIZE) { + slot->len < dev->ibi->max_payload_len) { mdatactrl = readl(master->regs + SVC_I3C_MDATACTRL); count = SVC_I3C_MDATACTRL_RXCOUNT(mdatactrl); + count = min(count, dev->ibi->max_payload_len - slot->len); readsb(master->regs + SVC_I3C_MRDATAB, buf, count); slot->len += count; buf += count; } + /* + * The device may have sent more than the requested payload. Drop the + * extra bytes so they do not leak into the next transfer. + */ + if (SVC_I3C_MSTATUS_RXPEND(readl(master->regs + SVC_I3C_MSTATUS))) + writel(SVC_I3C_MDATACTRL_FLUSHRB, master->regs + SVC_I3C_MDATACTRL); + master->ibi.tbq_slot = slot; return 0;