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[59.124.168.89]) by smtp.gmail.com with ESMTPSA id d9-20020a170902854900b0019f53e0f136sm12503965plo.232.2023.03.23.08.01.10 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 23 Mar 2023 08:01:13 -0700 (PDT) From: Andy Chiu To: linux-riscv@lists.infradead.org, palmer@dabbelt.com, anup@brainfault.org, atishp@atishpatra.org, kvm-riscv@lists.infradead.org, kvm@vger.kernel.org Cc: vineetg@rivosinc.com, greentime.hu@sifive.com, guoren@linux.alibaba.com, ShihPo Hung , Vincent Chen , Andy Chiu , Paul Walmsley , Albert Ou , Conor Dooley , Alexandre Ghiti , Masahiro Yamada , Guo Ren Subject: [PATCH -next v16 16/20] riscv: prevent stack corruption by reserving task_pt_regs(p) early Date: Thu, 23 Mar 2023 14:59:20 +0000 Message-Id: <20230323145924.4194-17-andy.chiu@sifive.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20230323145924.4194-1-andy.chiu@sifive.com> References: <20230323145924.4194-1-andy.chiu@sifive.com> Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org From: Greentime Hu Early function calls, such as setup_vm(), relocate_enable_mmu(), soc_early_init() etc, are free to operate on stack. However, PT_SIZE_ON_STACK bytes at the head of the kernel stack are purposedly reserved for the placement of per-task register context pointed by task_pt_regs(p). Those functions may corrupt task_pt_regs if we overlap the $sp with it. In fact, we had accidentally corrupted sstatus.VS in some tests, treating the kernel to save V context before V was actually allocated, resulting in a kernel panic. Thus, we should skip PT_SIZE_ON_STACK for $sp before making C function calls from the top-level assembly. Co-developed-by: ShihPo Hung Signed-off-by: ShihPo Hung Co-developed-by: Vincent Chen Signed-off-by: Vincent Chen Signed-off-by: Greentime Hu Signed-off-by: Andy Chiu Reviewed-by: Conor Dooley --- arch/riscv/kernel/head.S | 2 ++ 1 file changed, 2 insertions(+) diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S index e16bb2185d55..11c3b94c4534 100644 --- a/arch/riscv/kernel/head.S +++ b/arch/riscv/kernel/head.S @@ -301,6 +301,7 @@ clear_bss_done: la tp, init_task la sp, init_thread_union + THREAD_SIZE XIP_FIXUP_OFFSET sp + addi sp, sp, -PT_SIZE_ON_STACK #ifdef CONFIG_BUILTIN_DTB la a0, __dtb_start XIP_FIXUP_OFFSET a0 @@ -318,6 +319,7 @@ clear_bss_done: /* Restore C environment */ la tp, init_task la sp, init_thread_union + THREAD_SIZE + addi sp, sp, -PT_SIZE_ON_STACK #ifdef CONFIG_KASAN call kasan_early_init