Merge tag 'seccomp-3.17' of git://git.kernel.org/pub/scm/linux/kernel…

…/git/kees/linux into next

MAINTAINERS

@@ -7953,6 +7953,16 @@ S:	Maintained
 F:	drivers/mmc/host/sdhci.*
 F:	drivers/mmc/host/sdhci-pltfm.[ch]
 
+SECURE COMPUTING
+M:	Kees Cook <[email protected]>
+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 <[email protected]>
 L:	[email protected]

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

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

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

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 */

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

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

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

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

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

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

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? */

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
  */

include/linux/seccomp.h

@@ -3,6 +3,8 @@
 
 #include <uapi/linux/seccomp.h>
 
+#define SECCOMP_FILTER_FLAG_MASK	(SECCOMP_FILTER_FLAG_TSYNC)
+
 #ifdef CONFIG_SECCOMP
 
 #include <linux/thread_info.h>
@@ -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;

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

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,

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.

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(&current->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(&current->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