diff options
| -rw-r--r-- | arch/Kconfig | 6 | ||||
| -rw-r--r-- | include/linux/seccomp.h | 10 | ||||
| -rw-r--r-- | kernel/seccomp.c | 42 |
3 files changed, 42 insertions, 16 deletions
diff --git a/arch/Kconfig b/arch/Kconfig index 91c2c730fc1a..beaab68c13b7 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -220,8 +220,10 @@ config HAVE_ARCH_SECCOMP_FILTER bool help This symbol should be selected by an architecure if it provides - asm/syscall.h, specifically syscall_get_arguments() and - syscall_get_arch(). + asm/syscall.h, specifically syscall_get_arguments(), + syscall_get_arch(), and syscall_set_return_value(). Additionally, + its system call entry path must respect a return value of -1 from + __secure_computing() and/or secure_computing(). config SECCOMP_FILTER def_bool y diff --git a/include/linux/seccomp.h b/include/linux/seccomp.h index 86bb68fc7683..b4ce2c816e06 100644 --- a/include/linux/seccomp.h +++ b/include/linux/seccomp.h @@ -12,13 +12,14 @@ /* * All BPF programs must return a 32-bit value. - * The bottom 16-bits are reserved for future use. + * The bottom 16-bits are for optional return data. * The upper 16-bits are ordered from least permissive values to most. * * The ordering ensures that a min_t() over composed return values always * selects the least permissive choice. */ #define SECCOMP_RET_KILL 0x00000000U /* kill the task immediately */ +#define SECCOMP_RET_ERRNO 0x00050000U /* returns an errno */ #define SECCOMP_RET_ALLOW 0x7fff0000U /* allow */ /* Masks for the return value sections. */ @@ -64,11 +65,12 @@ struct seccomp { struct seccomp_filter *filter; }; -extern void __secure_computing(int); -static inline void secure_computing(int this_syscall) +extern int __secure_computing(int); +static inline int secure_computing(int this_syscall) { if (unlikely(test_thread_flag(TIF_SECCOMP))) - __secure_computing(this_syscall); + return __secure_computing(this_syscall); + return 0; } extern long prctl_get_seccomp(void); diff --git a/kernel/seccomp.c b/kernel/seccomp.c index 0f7c709a523e..5f78fb6d2212 100644 --- a/kernel/seccomp.c +++ b/kernel/seccomp.c @@ -199,15 +199,20 @@ static int seccomp_check_filter(struct sock_filter *filter, unsigned int flen) static u32 seccomp_run_filters(int syscall) { struct seccomp_filter *f; - u32 ret = SECCOMP_RET_KILL; + u32 ret = SECCOMP_RET_ALLOW; + + /* Ensure unexpected behavior doesn't result in failing open. */ + if (WARN_ON(current->seccomp.filter == NULL)) + return SECCOMP_RET_KILL; + /* * All filters in the list are evaluated and the lowest BPF return - * value always takes priority. + * value always takes priority (ignoring the DATA). */ for (f = current->seccomp.filter; f; f = f->prev) { - ret = sk_run_filter(NULL, f->insns); - if (ret != SECCOMP_RET_ALLOW) - break; + u32 cur_ret = sk_run_filter(NULL, f->insns); + if ((cur_ret & SECCOMP_RET_ACTION) < (ret & SECCOMP_RET_ACTION)) + ret = cur_ret; } return ret; } @@ -346,11 +351,13 @@ static int mode1_syscalls_32[] = { }; #endif -void __secure_computing(int this_syscall) +int __secure_computing(int this_syscall) { int mode = current->seccomp.mode; int exit_sig = 0; int *syscall; + u32 ret = SECCOMP_RET_KILL; + int data; switch (mode) { case SECCOMP_MODE_STRICT: @@ -361,14 +368,26 @@ void __secure_computing(int this_syscall) #endif do { if (*syscall == this_syscall) - return; + return 0; } while (*++syscall); exit_sig = SIGKILL; break; #ifdef CONFIG_SECCOMP_FILTER case SECCOMP_MODE_FILTER: - if (seccomp_run_filters(this_syscall) == SECCOMP_RET_ALLOW) - return; + ret = seccomp_run_filters(this_syscall); + data = ret & SECCOMP_RET_DATA; + switch (ret & SECCOMP_RET_ACTION) { + case SECCOMP_RET_ERRNO: + /* Set the low-order 16-bits as a errno. */ + syscall_set_return_value(current, task_pt_regs(current), + -data, 0); + goto skip; + case SECCOMP_RET_ALLOW: + return 0; + case SECCOMP_RET_KILL: + default: + break; + } exit_sig = SIGSYS; break; #endif @@ -379,8 +398,11 @@ void __secure_computing(int this_syscall) #ifdef SECCOMP_DEBUG dump_stack(); #endif - audit_seccomp(this_syscall, exit_code, SECCOMP_RET_KILL); + audit_seccomp(this_syscall, exit_sig, ret); do_exit(exit_sig); +skip: + audit_seccomp(this_syscall, exit_sig, ret); + return -1; } long prctl_get_seccomp(void) |