linux-kernel - [PATCH] riscv: process: fix kernel info leakage

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Date:   Sat, 29 Oct 2022 19:34:50 +0800
From:   Jisheng Zhang <jszhang@...nel.org>
To:     Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>, Guo Ren <guoren@...nel.org>
Cc:     linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH] riscv: process: fix kernel info leakage

thread_struct's s[12] may contain random kernel memory content, which
may be finally leaked to userspace. This is a security hole. Fix it
by clearing the s[12] array in thread_struct when fork.

As for kthread case, it's better to clear the s[12] array as well.

Fixes: 7db91e57a0ac ("RISC-V: Task implementation")
Signed-off-by: Jisheng Zhang <jszhang@...nel.org>
---

Previously, it's one of the series of "riscv: entry: further clean up
and VMAP_STACK fix". This is a fix, so I move it out of the series and
send it separately

 arch/riscv/kernel/process.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/riscv/kernel/process.c b/arch/riscv/kernel/process.c
index ceb9ebab6558..52002d54b163 100644
--- a/arch/riscv/kernel/process.c
+++ b/arch/riscv/kernel/process.c
@@ -164,6 +164,8 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
 	unsigned long tls = args->tls;
 	struct pt_regs *childregs = task_pt_regs(p);
 
+	memset(&p->thread.s, 0, sizeof(p->thread.s));
+
 	/* p->thread holds context to be restored by __switch_to() */
 	if (unlikely(args->fn)) {
 		/* Kernel thread */
-- 
2.37.2