diff options
| author | Mark Rutland <mark.rutland@arm.com> | 2016-03-01 14:18:50 +0000 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2016-07-27 09:47:33 -0700 |
| commit | cff5b236fa152d98bd83d901a0870a585414d340 (patch) | |
| tree | 9affb37b2a534d93ac200beb7b737fed14a9568c /arch/arm64/include/asm | |
| parent | de0f9fa7a50dafdfbc8e0558a39c872772fad6bb (diff) | |
arm64: Rework valid_user_regs
commit dbd4d7ca563fd0a8949718d35ce197e5642d5d9d upstream.
We validate pstate using PSR_MODE32_BIT, which is part of the
user-provided pstate (and cannot be trusted). Also, we conflate
validation of AArch32 and AArch64 pstate values, making the code
difficult to reason about.
Instead, validate the pstate value based on the associated task. The
task may or may not be current (e.g. when using ptrace), so this must be
passed explicitly by callers. To avoid circular header dependencies via
sched.h, is_compat_task is pulled out of asm/ptrace.h.
To make the code possible to reason about, the AArch64 and AArch32
validation is split into separate functions. Software must respect the
RES0 policy for SPSR bits, and thus the kernel mirrors the hardware
policy (RAZ/WI) for bits as-yet unallocated. When these acquire an
architected meaning writes may be permitted (potentially with additional
validation).
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Cc: Dave Martin <dave.martin@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
[ rebased for v4.1+
This avoids a user-triggerable Oops() if a task is switched to a mode
not supported by the kernel (e.g. switching a 64-bit task to AArch32).
]
Signed-off-by: James Morse <james.morse@arm.com>
Reviewed-by: Mark Rutland <mark.rutland@arm.com> [backport]
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'arch/arm64/include/asm')
| -rw-r--r-- | arch/arm64/include/asm/ptrace.h | 33 |
1 files changed, 4 insertions, 29 deletions
diff --git a/arch/arm64/include/asm/ptrace.h b/arch/arm64/include/asm/ptrace.h index e9e5467e0bf4..a307eb6e7fa8 100644 --- a/arch/arm64/include/asm/ptrace.h +++ b/arch/arm64/include/asm/ptrace.h @@ -58,6 +58,7 @@ #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 #ifdef CONFIG_CPU_BIG_ENDIAN #define COMPAT_PSR_ENDSTATE COMPAT_PSR_E_BIT @@ -151,35 +152,9 @@ 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) |