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bus: mhi: ep: Update read pointer only after buffer is written

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commit 6f18d174b73d0ceeaa341f46c0986436b3aefc9a upstream.

Inside mhi_ep_ring_add_element, the read pointer (rd_offset) is updated
before the buffer is written, potentially causing race conditions where
the host sees an updated read pointer before the buffer is actually
written. Updating rd_offset prematurely can lead to the host accessing
an uninitialized or incomplete element, resulting in data corruption.

Invoke the buffer write before updating rd_offset to ensure the element
is fully written before signaling its availability.

Fixes: bbdcba57a1 ("bus: mhi: ep: Add support for ring management")
cc: stable@vger.kernel.org
Co-developed-by: Youssef Samir <quic_yabdulra@quicinc.com>
Signed-off-by: Youssef Samir <quic_yabdulra@quicinc.com>
Signed-off-by: Sumit Kumar <quic_sumk@quicinc.com>
Reviewed-by: Jeff Hugo <jeff.hugo@oss.qualcomm.com>
Reviewed-by: Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Link: https://patch.msgid.link/20250409-rp_fix-v1-1-8cf1fa22ed28@quicinc.com
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Sumit Kumar
2025-04-09 16:17:43 +05:30
committed by Greg Kroah-Hartman
parent 838d63de34
commit 44b9620e82
1 changed files with 10 additions and 6 deletions
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16
drivers/bus/mhi/ep/ring.c
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@@ -131,19 +131,23 @@ int mhi_ep_ring_add_element(struct mhi_ep_ring *ring, struct mhi_ring_element *e
}
old_offset = ring->rd_offset;
mhi_ep_ring_inc_index(ring);
dev_dbg(dev, "Adding an element to ring at offset (%zu)\n", ring->rd_offset);
buf_info.host_addr = ring->rbase + (old_offset * sizeof(*el));
buf_info.dev_addr = el;
buf_info.size = sizeof(*el);
ret = mhi_cntrl->write_sync(mhi_cntrl, &buf_info);
if (ret)
return ret;
mhi_ep_ring_inc_index(ring);
/* Update rp in ring context */
rp = cpu_to_le64(ring->rd_offset * sizeof(*el) + ring->rbase);
memcpy_toio((void __iomem *) &ring->ring_ctx->generic.rp, &rp, sizeof(u64));
buf_info.host_addr = ring->rbase + (old_offset * sizeof(*el));
buf_info.dev_addr = el;
buf_info.size = sizeof(*el);
return mhi_cntrl->write_sync(mhi_cntrl, &buf_info);
return ret;
}
void mhi_ep_ring_init(struct mhi_ep_ring *ring, enum mhi_ep_ring_type type, u32 id)