From 49e9c99f47fc43abc9598f9fcf5ba3336d0c09a6 Mon Sep 17 00:00:00 2001 From: Ian Munsie Date: Wed, 29 Jun 2016 22:16:25 +1000 Subject: [PATCH] cxl: Fix allowing bogus AFU descriptors with 0 maximum processes If the AFU descriptor of an AFU directed AFU indicates that it supports 0 maximum processes, we will accept that value and attempt to use it. The SPA will still be allocated (with 2 pages due to another minor bug and room for 958 processes), and when a context is allocated we will pass the value of 0 to idr_alloc as the maximum. However, idr_alloc will treat that as meaning no maximum and will allocate a context number and we return a valid context. Conceivably, this could lead to a buffer overflow of the SPA if more than 958 contexts were allocated, however this is mitigated by the fact that there are no known AFUs in the wild with a bogus AFU descriptor like this, and that only the root user is allowed to flash an AFU image to a card. Add a check when validating the AFU descriptor to reject any with 0 maximum processes. We do still allow a dedicated process only AFU to indicate that it supports 0 contexts even though that is forbidden in the architecture, as in that case we ignore the value and use 1 instead. This is just on the off-chance that such a dedicated process AFU may exist (not that I am aware of any), since their developers are less likely to have cared about this value at all. Signed-off-by: Ian Munsie Reviewed-by: Frederic Barrat Reviewed-by: Andrew Donnellan Signed-off-by: Michael Ellerman --- drivers/misc/cxl/pci.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+) diff --git a/drivers/misc/cxl/pci.c b/drivers/misc/cxl/pci.c index 648817a2e219..58d7d8215964 100644 --- a/drivers/misc/cxl/pci.c +++ b/drivers/misc/cxl/pci.c @@ -775,6 +775,21 @@ static int cxl_afu_descriptor_looks_ok(struct cxl_afu *afu) } } + if ((afu->modes_supported & ~CXL_MODE_DEDICATED) && afu->max_procs_virtualised == 0) { + /* + * We could also check this for the dedicated process model + * since the architecture indicates it should be set to 1, but + * in that case we ignore the value and I'd rather not risk + * breaking any existing dedicated process AFUs that left it as + * 0 (not that I'm aware of any). It is clearly an error for an + * AFU directed AFU to set this to 0, and would have previously + * triggered a bug resulting in the maximum not being enforced + * at all since idr_alloc treats 0 as no maximum. + */ + dev_err(&afu->dev, "AFU does not support any processes\n"); + return -EINVAL; + } + return 0; } -- 2.20.1