[Mesa-dev] [Mesa-stable] [PATCH] st/clover: Don't segfault on clCreateBuffer with null context

[Aaron Watry]

I guess I misunderstood that obj() call (my IDE is misbehaving on the
machine I was doing that work on which limited my ability to easily
find function definitions outside of the current file).  C++ is pretty
unfamiliar to me and I guess that I figured that the obj() was some
alternative typecasting operation related to the typing for ctx not an
actual function call).  This'll teach me to stay away from C++ for a
while (again).

The segfault that I was actually encountering ended up being in
ocl-icd (version in the Ubuntu saucy repo).  When I built that project
straight from git, the segfault went away (there's been quite a few
null deref fixes in there since the version that Ubuntu 13.10
packages).  This was after I had already gone through the memory.cpp
code and broken my understanding of what it was doing.

FYI: I was attempting to run the create-buffer piglit CL API tests
(I'm working on a new extension of that for clCreateSubBuffer
testing).  It was disconcerting that the cl-api-create-buffer program
segfaulted reliably when encountering the test that attempts to
clCreateBuffer using a NULL context (line 264 in create-buffer.c).

Sorry for the noise.

--Aaron

On Thu, Apr 3, 2014 at 6:54 PM, Francisco Jerez <currojerez at riseup.net> wrote:
> Aaron Watry <awatry at gmail.com> writes:
>
>> This should fix a segfault in the case that you're not using ocl-icd.
>>
>> If you're using ocl-icd, make sure your version is new enough or you'll get
>> the segfault before you even get to clover.
>>
>> The null de-ref seems to have been introduced in 10.1, but earlier versions
>> have have also been affected in other ways.
>>
>
> NAK.  The obj() function already checks if the pointer is NULL.  Not
> sure how you're getting a segfault.
>
>> CC: "10.1" <mesa-stable at lists.freedesktop.org>
>>
>> Signed-off-by: Aaron Watry <awatry at gmail.com>
>> ---
>>  src/gallium/state_trackers/clover/api/memory.cpp | 3 +++
>>  1 file changed, 3 insertions(+)
>>
>> diff --git a/src/gallium/state_trackers/clover/api/memory.cpp b/src/gallium/state_trackers/clover/api/memory.cpp
>> index 7ed2191..dad5ad3 100644
>> --- a/src/gallium/state_trackers/clover/api/memory.cpp
>> +++ b/src/gallium/state_trackers/clover/api/memory.cpp
>> @@ -32,6 +32,9 @@ clCreateBuffer(cl_context d_ctx, cl_mem_flags flags, size_t size,
>>                 void *host_ptr, cl_int *r_errcode) try {
>>     auto &ctx = obj(d_ctx);
>>
>> +   if (d_ctx == NULL)
>> +        throw error(CL_INVALID_CONTEXT);
>> +
>>     if (bool(host_ptr) != bool(flags & (CL_MEM_USE_HOST_PTR |
>>                                         CL_MEM_COPY_HOST_PTR)))
>>        throw error(CL_INVALID_HOST_PTR);
>> --
>> 1.8.3.2
>>
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