Messages in this thread | | | Date | Fri, 13 Jan 2023 14:40:04 +0100 | From | Robert Richter <> | Subject | Re: [PATCH v2] cxl/mbox: Fix Payload Length check for Get Log command |
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On 13.01.23 11:53:54, Jonathan Cameron wrote: > On Wed, 4 Jan 2023 21:29:54 +0100 > Robert Richter <rrichter@amd.com> wrote: > > > Commit 2aeaf663b85e introduced strict checking for variable length > > payload size validation. The payload length of received data must > > match the size of the requested data by the caller except for the case > > where the min_out value is set. > > > > The Get Log command does not have a header with a length field set. > > The Log size is determined by the Get Supported Logs command (CXL 3.0, > > 8.2.9.5.1). However, the actual size can be smaller and the number of > > valid bytes in the payload output must be determined reading the > > Payload Length field (CXL 3.0, Table 8-36, Note 2). > > > > Two issues arise: The command can successfully complete with a payload > > length of zero. And, the valid payload length must then also be > > consumed by the caller. > > > > Change cxl_xfer_log() to pass the number of payload bytes back to the > > caller to determine the number of log entries. Implement the payload > > handling as a special case where mbox_cmd->size_out is consulted when > > cxl_internal_send_cmd() returns -EIO. A WARN_ONCE() is added to check > > that -EIO is only returned in case of an unexpected output size. > > > > Logs can be bigger than the maximum payload length and multiple Get > > Log commands can be issued. If the received payload size is smaller > > than the maximum payload size we can assume all valid bytes have been > > fetched. Stop sending further Get Log commands then. > > > > On that occasion, change debug messages to also report the opcodes of > > supported commands. > > > > The variable payload commands GET_LSA and SET_LSA could be also > > affected by this strict check, but SET_LSA cannot be broken because > > SET_LSA does not return an output payload, and GET_LSA never expects > > short reads. > > > > Fixes: 2aeaf663b85e ("cxl/mbox: Add variable output size validation for internal commands") > > Signed-off-by: Robert Richter <rrichter@amd.com> > Hi Robert, a few comments inline.
Oh, just found your comments here after replying to the other mail thread.
> > Thanks, > > Jonathan > > > --- > > drivers/cxl/core/mbox.c | 28 ++++++++++++++++++++-------- > > 1 file changed, 20 insertions(+), 8 deletions(-) > > > > diff --git a/drivers/cxl/core/mbox.c b/drivers/cxl/core/mbox.c > > index b03fba212799..e93df0d39022 100644 > > --- a/drivers/cxl/core/mbox.c > > +++ b/drivers/cxl/core/mbox.c > > @@ -170,6 +170,8 @@ int cxl_internal_send_cmd(struct cxl_dev_state *cxlds, > > out_size = mbox_cmd->size_out; > > min_out = mbox_cmd->min_out; > > rc = cxlds->mbox_send(cxlds, mbox_cmd); > > + if (WARN_ONCE(rc == -EIO, "Bad return code: -EIO")) > > This is unusual. Why the WARN_ONCE? How can an error code > be bad? It may well panic. Fine to have a dev_err() or similar > but this seems excessive.
This function should only return -EIO if the size is unexpected. The mbox_send() function doesn't have a size information and should never return with -EIO. I think a comment is need here?
> > > > + return -ENXIO; > > if (rc) > > return rc; > > > > @@ -576,6 +578,17 @@ static int cxl_xfer_log(struct cxl_dev_state *cxlds, uuid_t *uuid, u32 size, u8 > > }; > > > > rc = cxl_internal_send_cmd(cxlds, &mbox_cmd); > > + > > + /* > > + * The output payload length that indicates the number > > + * of valid bytes can be smaller than the Log buffer > > + * size. > > + */ > > + if (rc == -EIO && mbox_cmd.size_out < xfer_size) { > > + offset += mbox_cmd.size_out; > > + break; > > + } > > + > > if (rc < 0) > > return rc; > > > > @@ -584,7 +597,7 @@ static int cxl_xfer_log(struct cxl_dev_state *cxlds, uuid_t *uuid, u32 size, u8 > > offset += xfer_size; > > } > > > > - return 0; > > + return offset; > > } > > > > /** > > @@ -608,13 +621,11 @@ static void cxl_walk_cel(struct cxl_dev_state *cxlds, size_t size, u8 *cel) > > u16 opcode = le16_to_cpu(cel_entry[i].opcode); > > struct cxl_mem_command *cmd = cxl_mem_find_command(opcode); > > > > - if (!cmd) { > > - dev_dbg(cxlds->dev, > > - "Opcode 0x%04x unsupported by driver", opcode); > > - continue; > > - } > > + if (cmd) > > + set_bit(cmd->info.id, cxlds->enabled_cmds); > > > > - set_bit(cmd->info.id, cxlds->enabled_cmds); > > + dev_dbg(cxlds->dev, "Opcode 0x%04x %ssupported by driver", > > + opcode, cmd ? "" : "un"); > > Unrelated change so doesn't belong in this patch. I'd also split the > dev_dbg into two paths both to reduce modification and because people > might grep for "unsupported by driver"
I will send a separate patch for this and also rework this section.
> > > > } > > } > > > > @@ -695,11 +706,12 @@ int cxl_enumerate_cmds(struct cxl_dev_state *cxlds) > > } > > > > rc = cxl_xfer_log(cxlds, &uuid, size, log); > > - if (rc) { > > + if (rc < 0) { > > Feels like passing in size as a pointer that is then updated might be cleaner.
I can do that.
Thanks,
-Robert
> > > kvfree(log); > > goto out; > > } > > > > + size = (u32)rc; > > cxl_walk_cel(cxlds, size, log); > > kvfree(log); > > >
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