[PATCH] riscv: hwprobe: Avoid uninitialized read in hwprobe_get_cpus()

From: Mark Harris <mark.hsj@gmail.com>
To: Paul Walmsley <paul.walmsley@sifive.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Albert Ou <aou@eecs.berkeley.edu>
Cc: Alexandre Ghiti <alex@ghiti.fr>, Mark Harris <mark.hsj@gmail.com>,
	linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: [PATCH] riscv: hwprobe: Avoid uninitialized read in hwprobe_get_cpus()
Date: Thu, 11 Jun 2026 21:55:02 -0700	[thread overview]
Message-ID: <20260612045502.70850-1-mark.hsj@gmail.com> (raw)

When cpusetsize < cpumask_size(), hwprobe_get_cpus() did not fully
initialize its copy of the cpu mask, which could cause non-deterministic
results from the riscv_hwprobe syscall on a system with more than 8 CPUs
when the supplied cpu mask is empty.  Address this by fully initializing
the cpu mask.

Signed-off-by: Mark Harris <mark.hsj@gmail.com>
---
 arch/riscv/kernel/sys_hwprobe.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/riscv/kernel/sys_hwprobe.c b/arch/riscv/kernel/sys_hwprobe.c
index 1659d31fd288..caf6762427c8 100644
--- a/arch/riscv/kernel/sys_hwprobe.c
+++ b/arch/riscv/kernel/sys_hwprobe.c
@@ -450,6 +450,7 @@ static int hwprobe_get_cpus(struct riscv_hwprobe __user *pairs,
 	if (cpusetsize > cpumask_size())
 		cpusetsize = cpumask_size();
 
+	cpumask_clear(&cpus);
 	ret = copy_from_user(&cpus, cpus_user, cpusetsize);
 	if (ret)
 		return -EFAULT;
-- 
2.54.0


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