| Message ID | 20250409-rp_fix-v1-1-8cf1fa22ed28@quicinc.com |
|---|---|
| State | New |
| Headers | show |
| Series | bus: mhi: ep: Update read pointer only after buffer is written | expand |
On Wed, Apr 09, 2025 at 04:17:43PM +0530, Sumit Kumar wrote: > 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. > Hmm. I was under assumption that the host wouldn't access the rd_offset before raising the interrupt. But anyway, the fix looks legitimate irrespective of that. > Fixes: bbdcba57a1a2 ("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: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org> - Mani > --- > --- > drivers/bus/mhi/ep/ring.c | 16 ++++++++++------ > 1 file changed, 10 insertions(+), 6 deletions(-) > > diff --git a/drivers/bus/mhi/ep/ring.c b/drivers/bus/mhi/ep/ring.c > index aeb53b2c34a8cd859393529d0c8860462bc687ed..26357ee68dee984d70ae5bf39f8f09f2cbcafe30 100644 > --- a/drivers/bus/mhi/ep/ring.c > +++ b/drivers/bus/mhi/ep/ring.c > @@ -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) > > --- > base-commit: 1e26c5e28ca5821a824e90dd359556f5e9e7b89f > change-id: 20250328-rp_fix-d7ebc18bc3be > > Best regards, > -- > Sumit Kumar <quic_sumk@quicinc.com> >
On Wed, Apr 09, 2025 at 04:17:43PM +0530, Sumit Kumar wrote: > 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: bbdcba57a1a2 ("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> Applied to mhi-fixes! - Mani > --- > --- > drivers/bus/mhi/ep/ring.c | 16 ++++++++++------ > 1 file changed, 10 insertions(+), 6 deletions(-) > > diff --git a/drivers/bus/mhi/ep/ring.c b/drivers/bus/mhi/ep/ring.c > index aeb53b2c34a8cd859393529d0c8860462bc687ed..26357ee68dee984d70ae5bf39f8f09f2cbcafe30 100644 > --- a/drivers/bus/mhi/ep/ring.c > +++ b/drivers/bus/mhi/ep/ring.c > @@ -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) > > --- > base-commit: 1e26c5e28ca5821a824e90dd359556f5e9e7b89f > change-id: 20250328-rp_fix-d7ebc18bc3be > > Best regards, > -- > Sumit Kumar <quic_sumk@quicinc.com> >
diff --git a/drivers/bus/mhi/ep/ring.c b/drivers/bus/mhi/ep/ring.c index aeb53b2c34a8cd859393529d0c8860462bc687ed..26357ee68dee984d70ae5bf39f8f09f2cbcafe30 100644 --- a/drivers/bus/mhi/ep/ring.c +++ b/drivers/bus/mhi/ep/ring.c @@ -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)
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: bbdcba57a1a2 ("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> --- --- drivers/bus/mhi/ep/ring.c | 16 ++++++++++------ 1 file changed, 10 insertions(+), 6 deletions(-) --- base-commit: 1e26c5e28ca5821a824e90dd359556f5e9e7b89f change-id: 20250328-rp_fix-d7ebc18bc3be Best regards,