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riscv: Implement syscall wrappers 

Commit f0bddf5058 ("riscv: entry: Convert to generic entry") moved
syscall handling to C code, which exposed function pointer type
mismatches that trip fine-grained forward-edge Control-Flow Integrity
(CFI) checks as syscall handlers are all called through the same
syscall_t pointer type. To fix the type mismatches, implement pt_regs
based syscall wrappers similarly to x86 and arm64.

This patch is based on arm64 syscall wrappers added in commit
4378a7d4be ("arm64: implement syscall wrappers"), where the main goal
was to minimize the risk of userspace-controlled values being used
under speculation. This may be a concern for riscv in future as well.

Following other architectures, the syscall wrappers generate three
functions for each syscall; __riscv_<compat_>sys_<name> takes a pt_regs
pointer and extracts arguments from registers, __se_<compat_>sys_<name>
is a sign-extension wrapper that casts the long arguments to the
correct types for the real syscall implementation, which is named
__do_<compat_>sys_<name>.

Reviewed-by: Kees Cook <keescook@chromium.org>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Link: https://lore.kernel.org/r/20230710183544.999540-9-samitolvanen@google.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
This commit is contained in:
Sami Tolvanen 2023-07-10 18:35:46 +00:00 committed by Palmer Dabbelt
parent 06c2afb862
commit 08d0ce30e0
No known key found for this signature in database
GPG Key ID: 2E1319F35FBB1889
6 changed files with 108 additions and 7 deletions
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1
arch/riscv/Kconfig
View File

@ -35,6 +35,7 @@ config RISCV
select ARCH_HAS_SET_MEMORY if MMU
select ARCH_HAS_STRICT_KERNEL_RWX if MMU && !XIP_KERNEL
select ARCH_HAS_STRICT_MODULE_RWX if MMU && !XIP_KERNEL
select ARCH_HAS_SYSCALL_WRAPPER
select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
select ARCH_HAS_UBSAN_SANITIZE_ALL
select ARCH_HAS_VDSO_DATA

5
arch/riscv/include/asm/syscall.h
View File

@ -75,7 +75,7 @@ static inline int syscall_get_arch(struct task_struct *task)
#endif
}
typedef long (*syscall_t)(ulong, ulong, ulong, ulong, ulong, ulong, ulong);
typedef long (*syscall_t)(const struct pt_regs *);
static inline void syscall_handler(struct pt_regs *regs, ulong syscall)
{
syscall_t fn;
@ -87,8 +87,7 @@ static inline void syscall_handler(struct pt_regs *regs, ulong syscall)
#endif
fn = sys_call_table[syscall];
regs->a0 = fn(regs->orig_a0, regs->a1, regs->a2,
regs->a3, regs->a4, regs->a5, regs->a6);
regs->a0 = fn(regs);
}
static inline bool arch_syscall_is_vdso_sigreturn(struct pt_regs *regs)

87
arch/riscv/include/asm/syscall_wrapper.h Normal file
View File

@ -0,0 +1,87 @@
/* SPDX-License-Identifier: GPL-2.0 */
/*
* syscall_wrapper.h - riscv specific wrappers to syscall definitions
*
* Based on arch/arm64/include/syscall_wrapper.h
*/
#ifndef __ASM_SYSCALL_WRAPPER_H
#define __ASM_SYSCALL_WRAPPER_H
#include <asm/ptrace.h>
asmlinkage long __riscv_sys_ni_syscall(const struct pt_regs *);
#define SC_RISCV_REGS_TO_ARGS(x, ...) \
__MAP(x,__SC_ARGS \
,,regs->orig_a0,,regs->a1,,regs->a2 \
,,regs->a3,,regs->a4,,regs->a5,,regs->a6)
#ifdef CONFIG_COMPAT
#define COMPAT_SYSCALL_DEFINEx(x, name, ...) \
asmlinkage long __riscv_compat_sys##name(const struct pt_regs *regs); \
ALLOW_ERROR_INJECTION(__riscv_compat_sys##name, ERRNO); \
static long __se_compat_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__)); \
static inline long __do_compat_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__)); \
asmlinkage long __riscv_compat_sys##name(const struct pt_regs *regs) \
{ \
return __se_compat_sys##name(SC_RISCV_REGS_TO_ARGS(x,__VA_ARGS__)); \
} \
static long __se_compat_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__)) \
{ \
return __do_compat_sys##name(__MAP(x,__SC_DELOUSE,__VA_ARGS__)); \
} \
static inline long __do_compat_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__))
#define COMPAT_SYSCALL_DEFINE0(sname) \
asmlinkage long __riscv_compat_sys_##sname(const struct pt_regs *__unused); \
ALLOW_ERROR_INJECTION(__riscv_compat_sys_##sname, ERRNO); \
asmlinkage long __riscv_compat_sys_##sname(const struct pt_regs *__unused)
#define COND_SYSCALL_COMPAT(name) \
asmlinkage long __weak __riscv_compat_sys_##name(const struct pt_regs *regs); \
asmlinkage long __weak __riscv_compat_sys_##name(const struct pt_regs *regs) \
{ \
return sys_ni_syscall(); \
}
#define COMPAT_SYS_NI(name) \
SYSCALL_ALIAS(__riscv_compat_sys_##name, sys_ni_posix_timers);
#endif /* CONFIG_COMPAT */
#define __SYSCALL_DEFINEx(x, name, ...) \
asmlinkage long __riscv_sys##name(const struct pt_regs *regs); \
ALLOW_ERROR_INJECTION(__riscv_sys##name, ERRNO); \
static long __se_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__)); \
static inline long __do_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__)); \
asmlinkage long __riscv_sys##name(const struct pt_regs *regs) \
{ \
return __se_sys##name(SC_RISCV_REGS_TO_ARGS(x,__VA_ARGS__)); \
} \
static long __se_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__)) \
{ \
long ret = __do_sys##name(__MAP(x,__SC_CAST,__VA_ARGS__)); \
__MAP(x,__SC_TEST,__VA_ARGS__); \
__PROTECT(x, ret,__MAP(x,__SC_ARGS,__VA_ARGS__)); \
return ret; \
} \
static inline long __do_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__))
#define SYSCALL_DEFINE0(sname) \
SYSCALL_METADATA(_##sname, 0); \
asmlinkage long __riscv_sys_##sname(const struct pt_regs *__unused); \
ALLOW_ERROR_INJECTION(__riscv_sys_##sname, ERRNO); \
asmlinkage long __riscv_sys_##sname(const struct pt_regs *__unused)
#define COND_SYSCALL(name) \
asmlinkage long __weak __riscv_sys_##name(const struct pt_regs *regs); \
asmlinkage long __weak __riscv_sys_##name(const struct pt_regs *regs) \
{ \
return sys_ni_syscall(); \
}
#define SYS_NI(name) SYSCALL_ALIAS(__riscv_sys_##name, sys_ni_posix_timers);
#endif /* __ASM_SYSCALL_WRAPPER_H */

8
arch/riscv/kernel/compat_syscall_table.c
View File

@ -9,11 +9,15 @@
#include <asm/syscall.h>
#undef __SYSCALL
#define __SYSCALL(nr, call) [nr] = (call),
#define __SYSCALL(nr, call) asmlinkage long __riscv_##call(const struct pt_regs *);
#include <asm/unistd.h>
#undef __SYSCALL
#define __SYSCALL(nr, call) [nr] = __riscv_##call,
asmlinkage long compat_sys_rt_sigreturn(void);
void * const compat_sys_call_table[__NR_syscalls] = {
[0 ... __NR_syscalls - 1] = sys_ni_syscall,
[0 ... __NR_syscalls - 1] = __riscv_sys_ni_syscall,
#include <asm/unistd.h>
};

6
arch/riscv/kernel/sys_riscv.c
View File

@ -335,3 +335,9 @@ SYSCALL_DEFINE5(riscv_hwprobe, struct riscv_hwprobe __user *, pairs,
return do_riscv_hwprobe(pairs, pair_count, cpu_count,
cpus, flags);
}
/* Not defined using SYSCALL_DEFINE0 to avoid error injection */
asmlinkage long __riscv_sys_ni_syscall(const struct pt_regs *__unused)
{
return -ENOSYS;
}

8
arch/riscv/kernel/syscall_table.c
View File

@ -10,9 +10,13 @@
#include <asm/syscall.h>
#undef __SYSCALL
#define __SYSCALL(nr, call) [nr] = (call),
#define __SYSCALL(nr, call) asmlinkage long __riscv_##call(const struct pt_regs *);
#include <asm/unistd.h>
#undef __SYSCALL
#define __SYSCALL(nr, call) [nr] = __riscv_##call,
void * const sys_call_table[__NR_syscalls] = {
[0 ... __NR_syscalls - 1] = sys_ni_syscall,
[0 ... __NR_syscalls - 1] = __riscv_sys_ni_syscall,
#include <asm/unistd.h>
};