diff --git a/MAINTAINERS b/MAINTAINERS index e31c87474739..55762cba8516 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -7953,6 +7953,16 @@ S: Maintained F: drivers/mmc/host/sdhci.* F: drivers/mmc/host/sdhci-pltfm.[ch] +SECURE COMPUTING +M: Kees Cook +T: git git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux.git seccomp +S: Supported +F: kernel/seccomp.c +F: include/uapi/linux/seccomp.h +F: include/linux/seccomp.h +K: \bsecure_computing +K: \bTIF_SECCOMP\b + SECURE DIGITAL HOST CONTROLLER INTERFACE, OPEN FIRMWARE BINDINGS (SDHCI-OF) M: Anton Vorontsov L: linuxppc-dev@lists.ozlabs.org diff --git a/arch/Kconfig b/arch/Kconfig index 97ff872c7acc..0eae9df35b88 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -321,6 +321,7 @@ config HAVE_ARCH_SECCOMP_FILTER - secure_computing is called from a ptrace_event()-safe context - secure_computing return value is checked and a return value of -1 results in the system call being skipped immediately. + - seccomp syscall wired up config SECCOMP_FILTER def_bool y diff --git a/arch/arm/include/uapi/asm/unistd.h b/arch/arm/include/uapi/asm/unistd.h index ba94446c72d9..e21b4a069701 100644 --- a/arch/arm/include/uapi/asm/unistd.h +++ b/arch/arm/include/uapi/asm/unistd.h @@ -409,6 +409,7 @@ #define __NR_sched_setattr (__NR_SYSCALL_BASE+380) #define __NR_sched_getattr (__NR_SYSCALL_BASE+381) #define __NR_renameat2 (__NR_SYSCALL_BASE+382) +#define __NR_seccomp (__NR_SYSCALL_BASE+383) /* * This may need to be greater than __NR_last_syscall+1 in order to diff --git a/arch/arm/kernel/calls.S b/arch/arm/kernel/calls.S index 8f51bdcdacbb..bea85f97f363 100644 --- a/arch/arm/kernel/calls.S +++ b/arch/arm/kernel/calls.S @@ -392,6 +392,7 @@ /* 380 */ CALL(sys_sched_setattr) CALL(sys_sched_getattr) CALL(sys_renameat2) + CALL(sys_seccomp) #ifndef syscalls_counted .equ syscalls_padding, ((NR_syscalls + 3) & ~3) - NR_syscalls #define syscalls_counted diff --git a/arch/mips/include/uapi/asm/unistd.h b/arch/mips/include/uapi/asm/unistd.h index 5805414777e0..9bc13eaf9d67 100644 --- a/arch/mips/include/uapi/asm/unistd.h +++ b/arch/mips/include/uapi/asm/unistd.h @@ -372,16 +372,17 @@ #define __NR_sched_setattr (__NR_Linux + 349) #define __NR_sched_getattr (__NR_Linux + 350) #define __NR_renameat2 (__NR_Linux + 351) +#define __NR_seccomp (__NR_Linux + 352) /* * Offset of the last Linux o32 flavoured syscall */ -#define __NR_Linux_syscalls 351 +#define __NR_Linux_syscalls 352 #endif /* _MIPS_SIM == _MIPS_SIM_ABI32 */ #define __NR_O32_Linux 4000 -#define __NR_O32_Linux_syscalls 351 +#define __NR_O32_Linux_syscalls 352 #if _MIPS_SIM == _MIPS_SIM_ABI64 @@ -701,16 +702,17 @@ #define __NR_sched_setattr (__NR_Linux + 309) #define __NR_sched_getattr (__NR_Linux + 310) #define __NR_renameat2 (__NR_Linux + 311) +#define __NR_seccomp (__NR_Linux + 312) /* * Offset of the last Linux 64-bit flavoured syscall */ -#define __NR_Linux_syscalls 311 +#define __NR_Linux_syscalls 312 #endif /* _MIPS_SIM == _MIPS_SIM_ABI64 */ #define __NR_64_Linux 5000 -#define __NR_64_Linux_syscalls 311 +#define __NR_64_Linux_syscalls 312 #if _MIPS_SIM == _MIPS_SIM_NABI32 @@ -1034,15 +1036,16 @@ #define __NR_sched_setattr (__NR_Linux + 313) #define __NR_sched_getattr (__NR_Linux + 314) #define __NR_renameat2 (__NR_Linux + 315) +#define __NR_seccomp (__NR_Linux + 316) /* * Offset of the last N32 flavoured syscall */ -#define __NR_Linux_syscalls 315 +#define __NR_Linux_syscalls 316 #endif /* _MIPS_SIM == _MIPS_SIM_NABI32 */ #define __NR_N32_Linux 6000 -#define __NR_N32_Linux_syscalls 315 +#define __NR_N32_Linux_syscalls 316 #endif /* _UAPI_ASM_UNISTD_H */ diff --git a/arch/mips/kernel/scall32-o32.S b/arch/mips/kernel/scall32-o32.S index 3245474f19d5..ab02d14f1b5c 100644 --- a/arch/mips/kernel/scall32-o32.S +++ b/arch/mips/kernel/scall32-o32.S @@ -578,3 +578,4 @@ EXPORT(sys_call_table) PTR sys_sched_setattr PTR sys_sched_getattr /* 4350 */ PTR sys_renameat2 + PTR sys_seccomp diff --git a/arch/mips/kernel/scall64-64.S b/arch/mips/kernel/scall64-64.S index be2fedd4ae33..010dccf128ec 100644 --- a/arch/mips/kernel/scall64-64.S +++ b/arch/mips/kernel/scall64-64.S @@ -431,4 +431,5 @@ EXPORT(sys_call_table) PTR sys_sched_setattr PTR sys_sched_getattr /* 5310 */ PTR sys_renameat2 + PTR sys_seccomp .size sys_call_table,.-sys_call_table diff --git a/arch/mips/kernel/scall64-n32.S b/arch/mips/kernel/scall64-n32.S index c1dbcda4b816..c3b3b6525df5 100644 --- a/arch/mips/kernel/scall64-n32.S +++ b/arch/mips/kernel/scall64-n32.S @@ -424,4 +424,5 @@ EXPORT(sysn32_call_table) PTR sys_sched_setattr PTR sys_sched_getattr PTR sys_renameat2 /* 6315 */ + PTR sys_seccomp .size sysn32_call_table,.-sysn32_call_table diff --git a/arch/mips/kernel/scall64-o32.S b/arch/mips/kernel/scall64-o32.S index f1343ccd7ed7..bb1550b1f501 100644 --- a/arch/mips/kernel/scall64-o32.S +++ b/arch/mips/kernel/scall64-o32.S @@ -557,4 +557,5 @@ EXPORT(sys32_call_table) PTR sys_sched_setattr PTR sys_sched_getattr /* 4350 */ PTR sys_renameat2 + PTR sys_seccomp .size sys32_call_table,.-sys32_call_table diff --git a/arch/x86/syscalls/syscall_32.tbl b/arch/x86/syscalls/syscall_32.tbl index d6b867921612..7527eac24122 100644 --- a/arch/x86/syscalls/syscall_32.tbl +++ b/arch/x86/syscalls/syscall_32.tbl @@ -360,3 +360,4 @@ 351 i386 sched_setattr sys_sched_setattr 352 i386 sched_getattr sys_sched_getattr 353 i386 renameat2 sys_renameat2 +354 i386 seccomp sys_seccomp diff --git a/arch/x86/syscalls/syscall_64.tbl b/arch/x86/syscalls/syscall_64.tbl index ec255a1646d2..16272a6c12b7 100644 --- a/arch/x86/syscalls/syscall_64.tbl +++ b/arch/x86/syscalls/syscall_64.tbl @@ -323,6 +323,7 @@ 314 common sched_setattr sys_sched_setattr 315 common sched_getattr sys_sched_getattr 316 common renameat2 sys_renameat2 +317 common seccomp sys_seccomp # # x32-specific system call numbers start at 512 to avoid cache impact diff --git a/fs/exec.c b/fs/exec.c index a3d33fe592d6..ab1f1200ce5d 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -1216,7 +1216,7 @@ EXPORT_SYMBOL(install_exec_creds); /* * determine how safe it is to execute the proposed program * - the caller must hold ->cred_guard_mutex to protect against - * PTRACE_ATTACH + * PTRACE_ATTACH or seccomp thread-sync */ static void check_unsafe_exec(struct linux_binprm *bprm) { @@ -1234,7 +1234,7 @@ static void check_unsafe_exec(struct linux_binprm *bprm) * This isn't strictly necessary, but it makes it harder for LSMs to * mess up. */ - if (current->no_new_privs) + if (task_no_new_privs(current)) bprm->unsafe |= LSM_UNSAFE_NO_NEW_PRIVS; t = p; @@ -1272,7 +1272,7 @@ int prepare_binprm(struct linux_binprm *bprm) bprm->cred->egid = current_egid(); if (!(bprm->file->f_path.mnt->mnt_flags & MNT_NOSUID) && - !current->no_new_privs && + !task_no_new_privs(current) && kuid_has_mapping(bprm->cred->user_ns, inode->i_uid) && kgid_has_mapping(bprm->cred->user_ns, inode->i_gid)) { /* Set-uid? */ diff --git a/include/linux/sched.h b/include/linux/sched.h index 306f4f0c987a..0fd19055bb64 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1307,13 +1307,12 @@ struct task_struct { * execve */ unsigned in_iowait:1; - /* task may not gain privileges */ - unsigned no_new_privs:1; - /* Revert to default priority/policy when forking */ unsigned sched_reset_on_fork:1; unsigned sched_contributes_to_load:1; + unsigned long atomic_flags; /* Flags needing atomic access. */ + pid_t pid; pid_t tgid; @@ -1967,6 +1966,19 @@ static inline void memalloc_noio_restore(unsigned int flags) current->flags = (current->flags & ~PF_MEMALLOC_NOIO) | flags; } +/* Per-process atomic flags. */ +#define PFA_NO_NEW_PRIVS 0x00000001 /* May not gain new privileges. */ + +static inline bool task_no_new_privs(struct task_struct *p) +{ + return test_bit(PFA_NO_NEW_PRIVS, &p->atomic_flags); +} + +static inline void task_set_no_new_privs(struct task_struct *p) +{ + set_bit(PFA_NO_NEW_PRIVS, &p->atomic_flags); +} + /* * task->jobctl flags */ diff --git a/include/linux/seccomp.h b/include/linux/seccomp.h index 4054b0994071..5d586a45a319 100644 --- a/include/linux/seccomp.h +++ b/include/linux/seccomp.h @@ -3,6 +3,8 @@ #include +#define SECCOMP_FILTER_FLAG_MASK (SECCOMP_FILTER_FLAG_TSYNC) + #ifdef CONFIG_SECCOMP #include @@ -14,11 +16,11 @@ struct seccomp_filter; * * @mode: indicates one of the valid values above for controlled * system calls available to a process. - * @filter: The metadata and ruleset for determining what system calls - * are allowed for a task. + * @filter: must always point to a valid seccomp-filter or NULL as it is + * accessed without locking during system call entry. * * @filter must only be accessed from the context of current as there - * is no locking. + * is no read locking. */ struct seccomp { int mode; diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h index b0881a0ed322..1713977ee26f 100644 --- a/include/linux/syscalls.h +++ b/include/linux/syscalls.h @@ -866,4 +866,6 @@ asmlinkage long sys_process_vm_writev(pid_t pid, asmlinkage long sys_kcmp(pid_t pid1, pid_t pid2, int type, unsigned long idx1, unsigned long idx2); asmlinkage long sys_finit_module(int fd, const char __user *uargs, int flags); +asmlinkage long sys_seccomp(unsigned int op, unsigned int flags, + const char __user *uargs); #endif diff --git a/include/uapi/asm-generic/unistd.h b/include/uapi/asm-generic/unistd.h index 333640608087..65acbf0e2867 100644 --- a/include/uapi/asm-generic/unistd.h +++ b/include/uapi/asm-generic/unistd.h @@ -699,9 +699,11 @@ __SYSCALL(__NR_sched_setattr, sys_sched_setattr) __SYSCALL(__NR_sched_getattr, sys_sched_getattr) #define __NR_renameat2 276 __SYSCALL(__NR_renameat2, sys_renameat2) +#define __NR_seccomp 277 +__SYSCALL(__NR_seccomp, sys_seccomp) #undef __NR_syscalls -#define __NR_syscalls 277 +#define __NR_syscalls 278 /* * All syscalls below here should go away really, diff --git a/include/uapi/linux/seccomp.h b/include/uapi/linux/seccomp.h index ac2dc9f72973..0f238a43ff1e 100644 --- a/include/uapi/linux/seccomp.h +++ b/include/uapi/linux/seccomp.h @@ -10,6 +10,13 @@ #define SECCOMP_MODE_STRICT 1 /* uses hard-coded filter. */ #define SECCOMP_MODE_FILTER 2 /* uses user-supplied filter. */ +/* Valid operations for seccomp syscall. */ +#define SECCOMP_SET_MODE_STRICT 0 +#define SECCOMP_SET_MODE_FILTER 1 + +/* Valid flags for SECCOMP_SET_MODE_FILTER */ +#define SECCOMP_FILTER_FLAG_TSYNC 1 + /* * All BPF programs must return a 32-bit value. * The bottom 16-bits are for optional return data. diff --git a/kernel/fork.c b/kernel/fork.c index 6a13c46cd87d..ed4bc339c9dc 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -315,6 +315,15 @@ static struct task_struct *dup_task_struct(struct task_struct *orig) goto free_ti; tsk->stack = ti; +#ifdef CONFIG_SECCOMP + /* + * We must handle setting up seccomp filters once we're under + * the sighand lock in case orig has changed between now and + * then. Until then, filter must be NULL to avoid messing up + * the usage counts on the error path calling free_task. + */ + tsk->seccomp.filter = NULL; +#endif setup_thread_stack(tsk, orig); clear_user_return_notifier(tsk); @@ -1081,6 +1090,39 @@ static int copy_signal(unsigned long clone_flags, struct task_struct *tsk) return 0; } +static void copy_seccomp(struct task_struct *p) +{ +#ifdef CONFIG_SECCOMP + /* + * Must be called with sighand->lock held, which is common to + * all threads in the group. Holding cred_guard_mutex is not + * needed because this new task is not yet running and cannot + * be racing exec. + */ + BUG_ON(!spin_is_locked(¤t->sighand->siglock)); + + /* Ref-count the new filter user, and assign it. */ + get_seccomp_filter(current); + p->seccomp = current->seccomp; + + /* + * Explicitly enable no_new_privs here in case it got set + * between the task_struct being duplicated and holding the + * sighand lock. The seccomp state and nnp must be in sync. + */ + if (task_no_new_privs(current)) + task_set_no_new_privs(p); + + /* + * If the parent gained a seccomp mode after copying thread + * flags and between before we held the sighand lock, we have + * to manually enable the seccomp thread flag here. + */ + if (p->seccomp.mode != SECCOMP_MODE_DISABLED) + set_tsk_thread_flag(p, TIF_SECCOMP); +#endif +} + SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr) { current->clear_child_tid = tidptr; @@ -1196,7 +1238,6 @@ static struct task_struct *copy_process(unsigned long clone_flags, goto fork_out; ftrace_graph_init_task(p); - get_seccomp_filter(p); rt_mutex_init_task(p); @@ -1436,6 +1477,12 @@ static struct task_struct *copy_process(unsigned long clone_flags, spin_lock(¤t->sighand->siglock); + /* + * Copy seccomp details explicitly here, in case they were changed + * before holding sighand lock. + */ + copy_seccomp(p); + /* * Process group and session signals need to be delivered to just the * parent before the fork or both the parent and the child after the diff --git a/kernel/seccomp.c b/kernel/seccomp.c index 301bbc24739c..74f460179171 100644 --- a/kernel/seccomp.c +++ b/kernel/seccomp.c @@ -18,15 +18,17 @@ #include #include #include +#include +#include /* #define SECCOMP_DEBUG 1 */ #ifdef CONFIG_SECCOMP_FILTER #include #include +#include #include #include -#include #include #include @@ -172,21 +174,24 @@ static int seccomp_check_filter(struct sock_filter *filter, unsigned int flen) */ static u32 seccomp_run_filters(int syscall) { - struct seccomp_filter *f; + struct seccomp_filter *f = ACCESS_ONCE(current->seccomp.filter); struct seccomp_data sd; u32 ret = SECCOMP_RET_ALLOW; /* Ensure unexpected behavior doesn't result in failing open. */ - if (WARN_ON(current->seccomp.filter == NULL)) + if (unlikely(WARN_ON(f == NULL))) return SECCOMP_RET_KILL; + /* Make sure cross-thread synced filter points somewhere sane. */ + smp_read_barrier_depends(); + populate_seccomp_data(&sd); /* * All filters in the list are evaluated and the lowest BPF return * value always takes priority (ignoring the DATA). */ - for (f = current->seccomp.filter; f; f = f->prev) { + for (; f; f = f->prev) { u32 cur_ret = SK_RUN_FILTER(f->prog, (void *)&sd); if ((cur_ret & SECCOMP_RET_ACTION) < (ret & SECCOMP_RET_ACTION)) @@ -194,29 +199,159 @@ static u32 seccomp_run_filters(int syscall) } return ret; } +#endif /* CONFIG_SECCOMP_FILTER */ + +static inline bool seccomp_may_assign_mode(unsigned long seccomp_mode) +{ + BUG_ON(!spin_is_locked(¤t->sighand->siglock)); + + if (current->seccomp.mode && current->seccomp.mode != seccomp_mode) + return false; + + return true; +} + +static inline void seccomp_assign_mode(struct task_struct *task, + unsigned long seccomp_mode) +{ + BUG_ON(!spin_is_locked(&task->sighand->siglock)); + + task->seccomp.mode = seccomp_mode; + /* + * Make sure TIF_SECCOMP cannot be set before the mode (and + * filter) is set. + */ + smp_mb__before_atomic(); + set_tsk_thread_flag(task, TIF_SECCOMP); +} + +#ifdef CONFIG_SECCOMP_FILTER +/* Returns 1 if the parent is an ancestor of the child. */ +static int is_ancestor(struct seccomp_filter *parent, + struct seccomp_filter *child) +{ + /* NULL is the root ancestor. */ + if (parent == NULL) + return 1; + for (; child; child = child->prev) + if (child == parent) + return 1; + return 0; +} /** - * seccomp_attach_filter: Attaches a seccomp filter to current. + * seccomp_can_sync_threads: checks if all threads can be synchronized + * + * Expects sighand and cred_guard_mutex locks to be held. + * + * Returns 0 on success, -ve on error, or the pid of a thread which was + * either not in the correct seccomp mode or it did not have an ancestral + * seccomp filter. + */ +static inline pid_t seccomp_can_sync_threads(void) +{ + struct task_struct *thread, *caller; + + BUG_ON(!mutex_is_locked(¤t->signal->cred_guard_mutex)); + BUG_ON(!spin_is_locked(¤t->sighand->siglock)); + + /* Validate all threads being eligible for synchronization. */ + caller = current; + for_each_thread(caller, thread) { + pid_t failed; + + /* Skip current, since it is initiating the sync. */ + if (thread == caller) + continue; + + if (thread->seccomp.mode == SECCOMP_MODE_DISABLED || + (thread->seccomp.mode == SECCOMP_MODE_FILTER && + is_ancestor(thread->seccomp.filter, + caller->seccomp.filter))) + continue; + + /* Return the first thread that cannot be synchronized. */ + failed = task_pid_vnr(thread); + /* If the pid cannot be resolved, then return -ESRCH */ + if (unlikely(WARN_ON(failed == 0))) + failed = -ESRCH; + return failed; + } + + return 0; +} + +/** + * seccomp_sync_threads: sets all threads to use current's filter + * + * Expects sighand and cred_guard_mutex locks to be held, and for + * seccomp_can_sync_threads() to have returned success already + * without dropping the locks. + * + */ +static inline void seccomp_sync_threads(void) +{ + struct task_struct *thread, *caller; + + BUG_ON(!mutex_is_locked(¤t->signal->cred_guard_mutex)); + BUG_ON(!spin_is_locked(¤t->sighand->siglock)); + + /* Synchronize all threads. */ + caller = current; + for_each_thread(caller, thread) { + /* Skip current, since it needs no changes. */ + if (thread == caller) + continue; + + /* Get a task reference for the new leaf node. */ + get_seccomp_filter(caller); + /* + * Drop the task reference to the shared ancestor since + * current's path will hold a reference. (This also + * allows a put before the assignment.) + */ + put_seccomp_filter(thread); + smp_store_release(&thread->seccomp.filter, + caller->seccomp.filter); + /* + * Opt the other thread into seccomp if needed. + * As threads are considered to be trust-realm + * equivalent (see ptrace_may_access), it is safe to + * allow one thread to transition the other. + */ + if (thread->seccomp.mode == SECCOMP_MODE_DISABLED) { + /* + * Don't let an unprivileged task work around + * the no_new_privs restriction by creating + * a thread that sets it up, enters seccomp, + * then dies. + */ + if (task_no_new_privs(caller)) + task_set_no_new_privs(thread); + + seccomp_assign_mode(thread, SECCOMP_MODE_FILTER); + } + } +} + +/** + * seccomp_prepare_filter: Prepares a seccomp filter for use. * @fprog: BPF program to install * - * Returns 0 on success or an errno on failure. + * Returns filter on success or an ERR_PTR on failure. */ -static long seccomp_attach_filter(struct sock_fprog *fprog) +static struct seccomp_filter *seccomp_prepare_filter(struct sock_fprog *fprog) { struct seccomp_filter *filter; - unsigned long fp_size = fprog->len * sizeof(struct sock_filter); - unsigned long total_insns = fprog->len; + unsigned long fp_size; struct sock_filter *fp; int new_len; long ret; if (fprog->len == 0 || fprog->len > BPF_MAXINSNS) - return -EINVAL; - - for (filter = current->seccomp.filter; filter; filter = filter->prev) - total_insns += filter->prog->len + 4; /* include a 4 instr penalty */ - if (total_insns > MAX_INSNS_PER_PATH) - return -ENOMEM; + return ERR_PTR(-EINVAL); + BUG_ON(INT_MAX / fprog->len < sizeof(struct sock_filter)); + fp_size = fprog->len * sizeof(struct sock_filter); /* * Installing a seccomp filter requires that the task has @@ -224,14 +359,14 @@ static long seccomp_attach_filter(struct sock_fprog *fprog) * This avoids scenarios where unprivileged tasks can affect the * behavior of privileged children. */ - if (!current->no_new_privs && + if (!task_no_new_privs(current) && security_capable_noaudit(current_cred(), current_user_ns(), CAP_SYS_ADMIN) != 0) - return -EACCES; + return ERR_PTR(-EACCES); fp = kzalloc(fp_size, GFP_KERNEL|__GFP_NOWARN); if (!fp) - return -ENOMEM; + return ERR_PTR(-ENOMEM); /* Copy the instructions from fprog. */ ret = -EFAULT; @@ -275,13 +410,7 @@ static long seccomp_attach_filter(struct sock_fprog *fprog) sk_filter_select_runtime(filter->prog); - /* - * If there is an existing filter, make it the prev and don't drop its - * task reference. - */ - filter->prev = current->seccomp.filter; - current->seccomp.filter = filter; - return 0; + return filter; free_filter_prog: kfree(filter->prog); @@ -289,19 +418,20 @@ free_filter: kfree(filter); free_prog: kfree(fp); - return ret; + return ERR_PTR(ret); } /** - * seccomp_attach_user_filter - attaches a user-supplied sock_fprog + * seccomp_prepare_user_filter - prepares a user-supplied sock_fprog * @user_filter: pointer to the user data containing a sock_fprog. * * Returns 0 on success and non-zero otherwise. */ -static long seccomp_attach_user_filter(char __user *user_filter) +static struct seccomp_filter * +seccomp_prepare_user_filter(const char __user *user_filter) { struct sock_fprog fprog; - long ret = -EFAULT; + struct seccomp_filter *filter = ERR_PTR(-EFAULT); #ifdef CONFIG_COMPAT if (is_compat_task()) { @@ -314,9 +444,56 @@ static long seccomp_attach_user_filter(char __user *user_filter) #endif if (copy_from_user(&fprog, user_filter, sizeof(fprog))) goto out; - ret = seccomp_attach_filter(&fprog); + filter = seccomp_prepare_filter(&fprog); out: - return ret; + return filter; +} + +/** + * seccomp_attach_filter: validate and attach filter + * @flags: flags to change filter behavior + * @filter: seccomp filter to add to the current process + * + * Caller must be holding current->sighand->siglock lock. + * + * Returns 0 on success, -ve on error. + */ +static long seccomp_attach_filter(unsigned int flags, + struct seccomp_filter *filter) +{ + unsigned long total_insns; + struct seccomp_filter *walker; + + BUG_ON(!spin_is_locked(¤t->sighand->siglock)); + + /* Validate resulting filter length. */ + total_insns = filter->prog->len; + for (walker = current->seccomp.filter; walker; walker = walker->prev) + total_insns += walker->prog->len + 4; /* 4 instr penalty */ + if (total_insns > MAX_INSNS_PER_PATH) + return -ENOMEM; + + /* If thread sync has been requested, check that it is possible. */ + if (flags & SECCOMP_FILTER_FLAG_TSYNC) { + int ret; + + ret = seccomp_can_sync_threads(); + if (ret) + return ret; + } + + /* + * If there is an existing filter, make it the prev and don't drop its + * task reference. + */ + filter->prev = current->seccomp.filter; + current->seccomp.filter = filter; + + /* Now that the new filter is in place, synchronize to all threads. */ + if (flags & SECCOMP_FILTER_FLAG_TSYNC) + seccomp_sync_threads(); + + return 0; } /* get_seccomp_filter - increments the reference count of the filter on @tsk */ @@ -329,6 +506,14 @@ void get_seccomp_filter(struct task_struct *tsk) atomic_inc(&orig->usage); } +static inline void seccomp_filter_free(struct seccomp_filter *filter) +{ + if (filter) { + sk_filter_free(filter->prog); + kfree(filter); + } +} + /* put_seccomp_filter - decrements the ref count of tsk->seccomp.filter */ void put_seccomp_filter(struct task_struct *tsk) { @@ -337,8 +522,7 @@ void put_seccomp_filter(struct task_struct *tsk) while (orig && atomic_dec_and_test(&orig->usage)) { struct seccomp_filter *freeme = orig; orig = orig->prev; - sk_filter_free(freeme->prog); - kfree(freeme); + seccomp_filter_free(freeme); } } @@ -382,12 +566,17 @@ static int mode1_syscalls_32[] = { int __secure_computing(int this_syscall) { - int mode = current->seccomp.mode; int exit_sig = 0; int *syscall; u32 ret; - switch (mode) { + /* + * Make sure that any changes to mode from another thread have + * been seen after TIF_SECCOMP was seen. + */ + rmb(); + + switch (current->seccomp.mode) { case SECCOMP_MODE_STRICT: syscall = mode1_syscalls; #ifdef CONFIG_COMPAT @@ -473,47 +662,152 @@ long prctl_get_seccomp(void) } /** - * prctl_set_seccomp: configures current->seccomp.mode - * @seccomp_mode: requested mode to use - * @filter: optional struct sock_fprog for use with SECCOMP_MODE_FILTER - * - * This function may be called repeatedly with a @seccomp_mode of - * SECCOMP_MODE_FILTER to install additional filters. Every filter - * successfully installed will be evaluated (in reverse order) for each system - * call the task makes. + * seccomp_set_mode_strict: internal function for setting strict seccomp * * Once current->seccomp.mode is non-zero, it may not be changed. * * Returns 0 on success or -EINVAL on failure. */ -long prctl_set_seccomp(unsigned long seccomp_mode, char __user *filter) +static long seccomp_set_mode_strict(void) { + const unsigned long seccomp_mode = SECCOMP_MODE_STRICT; long ret = -EINVAL; - if (current->seccomp.mode && - current->seccomp.mode != seccomp_mode) + spin_lock_irq(¤t->sighand->siglock); + + if (!seccomp_may_assign_mode(seccomp_mode)) goto out; +#ifdef TIF_NOTSC + disable_TSC(); +#endif + seccomp_assign_mode(current, seccomp_mode); + ret = 0; + +out: + spin_unlock_irq(¤t->sighand->siglock); + + return ret; +} + +#ifdef CONFIG_SECCOMP_FILTER +/** + * seccomp_set_mode_filter: internal function for setting seccomp filter + * @flags: flags to change filter behavior + * @filter: struct sock_fprog containing filter + * + * This function may be called repeatedly to install additional filters. + * Every filter successfully installed will be evaluated (in reverse order) + * for each system call the task makes. + * + * Once current->seccomp.mode is non-zero, it may not be changed. + * + * Returns 0 on success or -EINVAL on failure. + */ +static long seccomp_set_mode_filter(unsigned int flags, + const char __user *filter) +{ + const unsigned long seccomp_mode = SECCOMP_MODE_FILTER; + struct seccomp_filter *prepared = NULL; + long ret = -EINVAL; + + /* Validate flags. */ + if (flags & ~SECCOMP_FILTER_FLAG_MASK) + return -EINVAL; + + /* Prepare the new filter before holding any locks. */ + prepared = seccomp_prepare_user_filter(filter); + if (IS_ERR(prepared)) + return PTR_ERR(prepared); + + /* + * Make sure we cannot change seccomp or nnp state via TSYNC + * while another thread is in the middle of calling exec. + */ + if (flags & SECCOMP_FILTER_FLAG_TSYNC && + mutex_lock_killable(¤t->signal->cred_guard_mutex)) + goto out_free; + + spin_lock_irq(¤t->sighand->siglock); + + if (!seccomp_may_assign_mode(seccomp_mode)) + goto out; + + ret = seccomp_attach_filter(flags, prepared); + if (ret) + goto out; + /* Do not free the successfully attached filter. */ + prepared = NULL; + + seccomp_assign_mode(current, seccomp_mode); +out: + spin_unlock_irq(¤t->sighand->siglock); + if (flags & SECCOMP_FILTER_FLAG_TSYNC) + mutex_unlock(¤t->signal->cred_guard_mutex); +out_free: + seccomp_filter_free(prepared); + return ret; +} +#else +static inline long seccomp_set_mode_filter(unsigned int flags, + const char __user *filter) +{ + return -EINVAL; +} +#endif + +/* Common entry point for both prctl and syscall. */ +static long do_seccomp(unsigned int op, unsigned int flags, + const char __user *uargs) +{ + switch (op) { + case SECCOMP_SET_MODE_STRICT: + if (flags != 0 || uargs != NULL) + return -EINVAL; + return seccomp_set_mode_strict(); + case SECCOMP_SET_MODE_FILTER: + return seccomp_set_mode_filter(flags, uargs); + default: + return -EINVAL; + } +} + +SYSCALL_DEFINE3(seccomp, unsigned int, op, unsigned int, flags, + const char __user *, uargs) +{ + return do_seccomp(op, flags, uargs); +} + +/** + * prctl_set_seccomp: configures current->seccomp.mode + * @seccomp_mode: requested mode to use + * @filter: optional struct sock_fprog for use with SECCOMP_MODE_FILTER + * + * Returns 0 on success or -EINVAL on failure. + */ +long prctl_set_seccomp(unsigned long seccomp_mode, char __user *filter) +{ + unsigned int op; + char __user *uargs; + switch (seccomp_mode) { case SECCOMP_MODE_STRICT: - ret = 0; -#ifdef TIF_NOTSC - disable_TSC(); -#endif + op = SECCOMP_SET_MODE_STRICT; + /* + * Setting strict mode through prctl always ignored filter, + * so make sure it is always NULL here to pass the internal + * check in do_seccomp(). + */ + uargs = NULL; break; -#ifdef CONFIG_SECCOMP_FILTER case SECCOMP_MODE_FILTER: - ret = seccomp_attach_user_filter(filter); - if (ret) - goto out; + op = SECCOMP_SET_MODE_FILTER; + uargs = filter; break; -#endif default: - goto out; + return -EINVAL; } - current->seccomp.mode = seccomp_mode; - set_thread_flag(TIF_SECCOMP); -out: - return ret; + /* prctl interface doesn't have flags, so they are always zero. */ + return do_seccomp(op, 0, uargs); } diff --git a/kernel/sys.c b/kernel/sys.c index 66a751ebf9d9..ce8129192a26 100644 --- a/kernel/sys.c +++ b/kernel/sys.c @@ -1990,12 +1990,12 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3, if (arg2 != 1 || arg3 || arg4 || arg5) return -EINVAL; - current->no_new_privs = 1; + task_set_no_new_privs(current); break; case PR_GET_NO_NEW_PRIVS: if (arg2 || arg3 || arg4 || arg5) return -EINVAL; - return current->no_new_privs ? 1 : 0; + return task_no_new_privs(current) ? 1 : 0; case PR_GET_THP_DISABLE: if (arg2 || arg3 || arg4 || arg5) return -EINVAL; diff --git a/kernel/sys_ni.c b/kernel/sys_ni.c index 36441b51b5df..2904a2105914 100644 --- a/kernel/sys_ni.c +++ b/kernel/sys_ni.c @@ -213,3 +213,6 @@ cond_syscall(compat_sys_open_by_handle_at); /* compare kernel pointers */ cond_syscall(sys_kcmp); + +/* operate on Secure Computing state */ +cond_syscall(sys_seccomp); diff --git a/security/apparmor/domain.c b/security/apparmor/domain.c index 452567d3a08e..d97cba3e3849 100644 --- a/security/apparmor/domain.c +++ b/security/apparmor/domain.c @@ -621,7 +621,7 @@ int aa_change_hat(const char *hats[], int count, u64 token, bool permtest) * There is no exception for unconfined as change_hat is not * available. */ - if (current->no_new_privs) + if (task_no_new_privs(current)) return -EPERM; /* released below */ @@ -776,7 +776,7 @@ int aa_change_profile(const char *ns_name, const char *hname, bool onexec, * no_new_privs is set because this aways results in a reduction * of permissions. */ - if (current->no_new_privs && !unconfined(profile)) { + if (task_no_new_privs(current) && !unconfined(profile)) { put_cred(cred); return -EPERM; }