From: Jisheng Zhang <jszhang@kernel.org> To: Paul Walmsley <paul.walmsley@sifive.com>, Palmer Dabbelt <palmer@dabbelt.com>, Albert Ou <aou@eecs.berkeley.edu>, Guo Ren <guoren@kernel.org> Cc: linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org Subject: [PATCH v3] riscv: fix race when vmap stack overflow Date: Sun, 30 Oct 2022 20:45:17 +0800 [thread overview] Message-ID: <20221030124517.2370-1-jszhang@kernel.org> (raw) Currently, when detecting vmap stack overflow, riscv firstly switches to the so called shadow stack, then use this shadow stack to call the get_overflow_stack() to get the overflow stack. However, there's a race here if two or more harts use the same shadow stack at the same time. To solve this race, we introduce spin_shadow_stack atomic var, which will be swap between its own address and 0 in atomic way, when the var is set, it means the shadow_stack is being used; when the var is cleared, it means the shadow_stack isn't being used. Fixes: 31da94c25aea ("riscv: add VMAP_STACK overflow detection") Signed-off-by: Jisheng Zhang <jszhang@kernel.org> Suggested-by: Guo Ren <guoren@kernel.org> --- Since v2: - use REG_AMOSWAP - add comment to the purpose of smp_store_release() Since v1: - use smp_store_release directly - use unsigned int instead of atomic_t arch/riscv/include/asm/asm.h | 1 + arch/riscv/kernel/entry.S | 4 ++++ arch/riscv/kernel/traps.c | 9 +++++++++ 3 files changed, 14 insertions(+) diff --git a/arch/riscv/include/asm/asm.h b/arch/riscv/include/asm/asm.h index 1b471ff73178..acf563072b8b 100644 --- a/arch/riscv/include/asm/asm.h +++ b/arch/riscv/include/asm/asm.h @@ -23,6 +23,7 @@ #define REG_L __REG_SEL(ld, lw) #define REG_S __REG_SEL(sd, sw) #define REG_SC __REG_SEL(sc.d, sc.w) +#define REG_AMOSWAP __REG_SEL(amoswap.d, amoswap.w) #define REG_ASM __REG_SEL(.dword, .word) #define SZREG __REG_SEL(8, 4) #define LGREG __REG_SEL(3, 2) diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S index b9eda3fcbd6d..ea6b78dac739 100644 --- a/arch/riscv/kernel/entry.S +++ b/arch/riscv/kernel/entry.S @@ -404,6 +404,10 @@ handle_syscall_trace_exit: #ifdef CONFIG_VMAP_STACK handle_kernel_stack_overflow: +1: la sp, spin_shadow_stack + REG_AMOSWAP sp, sp, (sp) + bnez sp, 1b + la sp, shadow_stack addi sp, sp, SHADOW_OVERFLOW_STACK_SIZE diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c index f3e96d60a2ff..dea47f329708 100644 --- a/arch/riscv/kernel/traps.c +++ b/arch/riscv/kernel/traps.c @@ -221,11 +221,20 @@ asmlinkage unsigned long get_overflow_stack(void) OVERFLOW_STACK_SIZE; } +unsigned long spin_shadow_stack; + asmlinkage void handle_bad_stack(struct pt_regs *regs) { unsigned long tsk_stk = (unsigned long)current->stack; unsigned long ovf_stk = (unsigned long)this_cpu_ptr(overflow_stack); + /* + * to ensure spin flag is set after the sp is used in entry.S: + * //load per-cpu overflow stack. + * REG_L sp, -8(sp) + */ + smp_store_release(&spin_shadow_stack, 0); + console_verbose(); pr_emerg("Insufficient stack space to handle exception!\n"); -- 2.37.2
WARNING: multiple messages have this Message-ID (diff)
From: Jisheng Zhang <jszhang@kernel.org> To: Paul Walmsley <paul.walmsley@sifive.com>, Palmer Dabbelt <palmer@dabbelt.com>, Albert Ou <aou@eecs.berkeley.edu>, Guo Ren <guoren@kernel.org> Cc: linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org Subject: [PATCH v3] riscv: fix race when vmap stack overflow Date: Sun, 30 Oct 2022 20:45:17 +0800 [thread overview] Message-ID: <20221030124517.2370-1-jszhang@kernel.org> (raw) Currently, when detecting vmap stack overflow, riscv firstly switches to the so called shadow stack, then use this shadow stack to call the get_overflow_stack() to get the overflow stack. However, there's a race here if two or more harts use the same shadow stack at the same time. To solve this race, we introduce spin_shadow_stack atomic var, which will be swap between its own address and 0 in atomic way, when the var is set, it means the shadow_stack is being used; when the var is cleared, it means the shadow_stack isn't being used. Fixes: 31da94c25aea ("riscv: add VMAP_STACK overflow detection") Signed-off-by: Jisheng Zhang <jszhang@kernel.org> Suggested-by: Guo Ren <guoren@kernel.org> --- Since v2: - use REG_AMOSWAP - add comment to the purpose of smp_store_release() Since v1: - use smp_store_release directly - use unsigned int instead of atomic_t arch/riscv/include/asm/asm.h | 1 + arch/riscv/kernel/entry.S | 4 ++++ arch/riscv/kernel/traps.c | 9 +++++++++ 3 files changed, 14 insertions(+) diff --git a/arch/riscv/include/asm/asm.h b/arch/riscv/include/asm/asm.h index 1b471ff73178..acf563072b8b 100644 --- a/arch/riscv/include/asm/asm.h +++ b/arch/riscv/include/asm/asm.h @@ -23,6 +23,7 @@ #define REG_L __REG_SEL(ld, lw) #define REG_S __REG_SEL(sd, sw) #define REG_SC __REG_SEL(sc.d, sc.w) +#define REG_AMOSWAP __REG_SEL(amoswap.d, amoswap.w) #define REG_ASM __REG_SEL(.dword, .word) #define SZREG __REG_SEL(8, 4) #define LGREG __REG_SEL(3, 2) diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S index b9eda3fcbd6d..ea6b78dac739 100644 --- a/arch/riscv/kernel/entry.S +++ b/arch/riscv/kernel/entry.S @@ -404,6 +404,10 @@ handle_syscall_trace_exit: #ifdef CONFIG_VMAP_STACK handle_kernel_stack_overflow: +1: la sp, spin_shadow_stack + REG_AMOSWAP sp, sp, (sp) + bnez sp, 1b + la sp, shadow_stack addi sp, sp, SHADOW_OVERFLOW_STACK_SIZE diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c index f3e96d60a2ff..dea47f329708 100644 --- a/arch/riscv/kernel/traps.c +++ b/arch/riscv/kernel/traps.c @@ -221,11 +221,20 @@ asmlinkage unsigned long get_overflow_stack(void) OVERFLOW_STACK_SIZE; } +unsigned long spin_shadow_stack; + asmlinkage void handle_bad_stack(struct pt_regs *regs) { unsigned long tsk_stk = (unsigned long)current->stack; unsigned long ovf_stk = (unsigned long)this_cpu_ptr(overflow_stack); + /* + * to ensure spin flag is set after the sp is used in entry.S: + * //load per-cpu overflow stack. + * REG_L sp, -8(sp) + */ + smp_store_release(&spin_shadow_stack, 0); + console_verbose(); pr_emerg("Insufficient stack space to handle exception!\n"); -- 2.37.2 _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv
next reply other threads:[~2022-10-30 12:55 UTC|newest] Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-10-30 12:45 Jisheng Zhang [this message] 2022-10-30 12:45 ` [PATCH v3] riscv: fix race when vmap stack overflow Jisheng Zhang 2022-10-30 13:23 ` Guo Ren 2022-10-30 13:23 ` Guo Ren 2022-11-23 15:23 ` Jisheng Zhang 2022-11-23 15:23 ` Jisheng Zhang 2022-11-30 2:29 ` Palmer Dabbelt 2022-11-30 2:29 ` Palmer Dabbelt
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