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RDMA/core: Validate cpu_id against nr_cpu_ids in DMAH alloc

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The cpu_id attribute supplied by user space through
UVERBS_ATTR_ALLOC_DMAH_CPU_ID is passed directly to cpumask_test_cpu()
without first verifying that the value is within the valid CPU range.

Passing such untrusted data to cpumask_test_cpu() may lead to an
out-of-bounds read of the underlying cpumask bitmap: the helper expands
to a test_bit() that indexes the bitmap by cpu_id / BITS_PER_LONG with
no bound check.

In addition, on kernels built with CONFIG_DEBUG_PER_CPU_MAPS it trips
the WARN_ON_ONCE() in cpumask_check(); combined with panic_on_warn this
turns a bad user input into a machine reboot.

Reject any cpu_id that is not smaller than nr_cpu_ids with -EINVAL
before it is used.

Reported by Smatch.

Fixes: d83edab562 ("RDMA/core: Introduce a DMAH object and its alloc/free APIs")
Link: https://patch.msgid.link/r/20260525142136.28165-1-yishaih@nvidia.com
Cc: stable@vger.kernel.org
Reported-by: Dan Carpenter <error27@gmail.com>
Closes: https://lore.kernel.org/r/ag68qoAW3P04J7pT@stanley.mountain/
Signed-off-by: Yishai Hadas <yishaih@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
This commit is contained in:
Yishai Hadas 2026-05-25 17:21:36 +03:00 • committed by Jason Gunthorpe
commit 323c98a4ff
1 changed files with 5 additions and 0 deletions
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5
drivers/infiniband/core/uverbs_std_types_dmah.c
View file

@ -47,6 +47,11 @@ static int UVERBS_HANDLER(UVERBS_METHOD_DMAH_ALLOC)(
if (ret)
goto err;
if (dmah->cpu_id >= nr_cpu_ids) {
ret = -EINVAL;
goto err;
}
if (!cpumask_test_cpu(dmah->cpu_id, current->cpus_ptr)) {
ret = -EPERM;
goto err;