diff --git a/arch/arm64/include/asm/ptrace.h b/arch/arm64/include/asm/ptrace.h index 88d6e2436808..300a382ed88f 100644 --- a/arch/arm64/include/asm/ptrace.h +++ b/arch/arm64/include/asm/ptrace.h @@ -58,6 +58,8 @@ #define COMPAT_PSR_Z_BIT 0x40000000 #define COMPAT_PSR_N_BIT 0x80000000 #define COMPAT_PSR_IT_MASK 0x0600fc00 /* If-Then execution state mask */ +#define COMPAT_PSR_GE_MASK 0x000f0000 + /* * These are 'magic' values for PTRACE_PEEKUSR that return info about where a * process is located in memory. @@ -144,35 +146,9 @@ static inline unsigned long regs_return_value(struct pt_regs *regs) return regs->regs[0]; } -/* - * Are the current registers suitable for user mode? (used to maintain - * security in signal handlers) - */ -static inline int valid_user_regs(struct user_pt_regs *regs) -{ - if (user_mode(regs) && (regs->pstate & PSR_I_BIT) == 0) { - regs->pstate &= ~(PSR_F_BIT | PSR_A_BIT); - - /* The T bit is reserved for AArch64 */ - if (!(regs->pstate & PSR_MODE32_BIT)) - regs->pstate &= ~COMPAT_PSR_T_BIT; - - return 1; - } - - /* - * Force PSR to something logical... - */ - regs->pstate &= PSR_f | PSR_s | (PSR_x & ~PSR_A_BIT) | \ - COMPAT_PSR_T_BIT | PSR_MODE32_BIT; - - if (!(regs->pstate & PSR_MODE32_BIT)) { - regs->pstate &= ~COMPAT_PSR_T_BIT; - regs->pstate |= PSR_MODE_EL0t; - } - - return 0; -} +/* We must avoid circular header include via sched.h */ +struct task_struct; +int valid_user_regs(struct user_pt_regs *regs, struct task_struct *task); #define instruction_pointer(regs) ((unsigned long)(regs)->pc) diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c index 3dc81f024c1b..53bdc598d1c1 100644 --- a/arch/arm64/kernel/ptrace.c +++ b/arch/arm64/kernel/ptrace.c @@ -45,6 +45,10 @@ #define CREATE_TRACE_POINTS #include +#ifndef DBG_SPSR_SS +#define DBG_SPSR_SS (1 << 21) +#endif + /* * TODO: does not yet catch signals sent when the child dies. * in exit.c or in signal.c. @@ -501,7 +505,7 @@ static int gpr_set(struct task_struct *target, const struct user_regset *regset, if (ret) return ret; - if (!valid_user_regs(&newregs)) + if (!valid_user_regs(&newregs, target)) return -EINVAL; task_pt_regs(target)->user_regs = newregs; @@ -733,7 +737,7 @@ static int compat_gpr_set(struct task_struct *target, } - if (valid_user_regs(&newregs.user_regs)) + if (valid_user_regs(&newregs.user_regs, target)) *task_pt_regs(target) = newregs; else ret = -EINVAL; @@ -1138,3 +1142,78 @@ asmlinkage void syscall_trace_exit(struct pt_regs *regs) if (test_thread_flag(TIF_SYSCALL_TRACE)) tracehook_report_syscall(regs, PTRACE_SYSCALL_EXIT); } + +/* + * Bits which are always architecturally RES0 per ARM DDI 0487A.h + * Userspace cannot use these until they have an architectural meaning. + * We also reserve IL for the kernel; SS is handled dynamically. + */ +#define SPSR_EL1_AARCH64_RES0_BITS \ + (GENMASK_ULL(63,32) | GENMASK_ULL(27, 22) | GENMASK_ULL(20, 10) | \ + GENMASK_ULL(5, 5)) +#define SPSR_EL1_AARCH32_RES0_BITS \ + (GENMASK_ULL(63,32) | GENMASK_ULL(24, 22) | GENMASK_ULL(20,20)) + +static int valid_compat_regs(struct user_pt_regs *regs) +{ + regs->pstate &= ~SPSR_EL1_AARCH32_RES0_BITS; + + /* Force kernel endianness on user space */ + if (IS_ENABLED(CONFIG_CPU_BIG_ENDIAN)) + regs->pstate |= COMPAT_PSR_E_BIT; + else + regs->pstate &= ~COMPAT_PSR_E_BIT; + + if (user_mode(regs) && (regs->pstate & PSR_MODE32_BIT) && + (regs->pstate & COMPAT_PSR_A_BIT) == 0 && + (regs->pstate & COMPAT_PSR_I_BIT) == 0 && + (regs->pstate & COMPAT_PSR_F_BIT) == 0) { + return 1; + } + + /* + * Force PSR to a valid 32-bit EL0t, preserving the same bits as + * arch/arm. + */ + regs->pstate &= COMPAT_PSR_N_BIT | COMPAT_PSR_Z_BIT | + COMPAT_PSR_C_BIT | COMPAT_PSR_V_BIT | + COMPAT_PSR_Q_BIT | COMPAT_PSR_IT_MASK | + COMPAT_PSR_GE_MASK | COMPAT_PSR_E_BIT | + COMPAT_PSR_T_BIT; + regs->pstate |= PSR_MODE32_BIT; + + return 0; +} + +static int valid_native_regs(struct user_pt_regs *regs) +{ + regs->pstate &= ~SPSR_EL1_AARCH64_RES0_BITS; + + if (user_mode(regs) && !(regs->pstate & PSR_MODE32_BIT) && + (regs->pstate & PSR_D_BIT) == 0 && + (regs->pstate & PSR_A_BIT) == 0 && + (regs->pstate & PSR_I_BIT) == 0 && + (regs->pstate & PSR_F_BIT) == 0) { + return 1; + } + + /* Force PSR to a valid 64-bit EL0t */ + regs->pstate &= PSR_N_BIT | PSR_Z_BIT | PSR_C_BIT | PSR_V_BIT; + + return 0; +} + +/* + * Are the current registers suitable for user mode? (used to maintain + * security in signal handlers) + */ +int valid_user_regs(struct user_pt_regs *regs, struct task_struct *task) +{ + if (!test_tsk_thread_flag(task, TIF_SINGLESTEP)) + regs->pstate &= ~DBG_SPSR_SS; + + if (is_compat_thread(task_thread_info(task))) + return valid_compat_regs(regs); + else + return valid_native_regs(regs); +} diff --git a/arch/arm64/kernel/signal.c b/arch/arm64/kernel/signal.c index 6357b9c6c90e..d1ae7c217ba9 100644 --- a/arch/arm64/kernel/signal.c +++ b/arch/arm64/kernel/signal.c @@ -115,7 +115,7 @@ static int restore_sigframe(struct pt_regs *regs, */ regs->syscallno = ~0UL; - err |= !valid_user_regs(®s->user_regs); + err |= !valid_user_regs(®s->user_regs, current); if (err == 0) { struct fpsimd_context *fpsimd_ctx = @@ -322,7 +322,7 @@ static void handle_signal(unsigned long sig, struct k_sigaction *ka, /* * Check that the resulting registers are actually sane. */ - ret |= !valid_user_regs(®s->user_regs); + ret |= !valid_user_regs(®s->user_regs, current); if (ret != 0) { force_sigsegv(sig, tsk); diff --git a/arch/arm64/kernel/signal32.c b/arch/arm64/kernel/signal32.c index e3ac8f0c0fc7..03520c650701 100644 --- a/arch/arm64/kernel/signal32.c +++ b/arch/arm64/kernel/signal32.c @@ -350,7 +350,7 @@ static int compat_restore_sigframe(struct pt_regs *regs, */ regs->syscallno = ~0UL; - err |= !valid_user_regs(®s->user_regs); + err |= !valid_user_regs(®s->user_regs, current); aux = (struct compat_aux_sigframe __user *) sf->uc.uc_regspace; if (err == 0)