Improve input validation of system call

This commit revents crashes from invalid parameters. In addition, it
adds missing ERR_TASK_CANT_REMOVE error code definition.

Author: jserv

kernel/error.c

@@ -13,6 +13,7 @@ static const struct error_code error_desc[] = {
     {ERR_TCB_ALLOC, "TCB allocation"},
     {ERR_STACK_ALLOC, "stack allocation"},
     {ERR_TASK_NOT_FOUND, "task not found"},
+    {ERR_TASK_CANT_REMOVE, "cannot remove task"},
     {ERR_TASK_CANT_SUSPEND, "cannot suspend task"},
     {ERR_TASK_CANT_RESUME, "cannot resume task"},
     {ERR_TASK_INVALID_PRIO, "invalid task priority"},

kernel/syscall.c

@@ -4,6 +4,7 @@
 #include <sys/task.h>
 
 #include "private/stdio.h"
+#include "private/utils.h"
 
 /* syscall wrappers */
 #define _(name, num, rettype, arglist) static rettype _##name arglist;
@@ -18,8 +19,13 @@ static const void *syscall_table[SYS_COUNT] = {SYSCALL_TABLE};
 /* Weak, generic dispatcher */
 int syscall(int num, void *a1, void *a2, void *a3)
 {
-    if (num <= 0 || num >= SYS_COUNT)
+    if (unlikely(num <= 0 || num >= SYS_COUNT))
         return -ENOSYS;
+
+    /* safety check for valid function pointer */
+    if (unlikely(!syscall_table[num]))
+        return -ENOSYS;
+
     return ((int (*)(void *, void *, void *)) syscall_table[num])(a1, a2, a3);
 }
 
@@ -84,40 +90,71 @@ static int _sbrk(int incr)
     extern uint32_t _end, _stack;
     static char *brk = (char *) &_end;
     char *prev = brk;
-    if (brk + incr >= (char *) &_stack) {
+
+    if (unlikely(incr < 0)) {
+        errno = EINVAL;
+        return -1;
+    }
+
+    if (unlikely(brk + incr >= (char *) &_stack)) {
         errno = ENOMEM;
         return -1;
     }
+
     brk += incr;
     return (int) prev;
 }
 
 static int _usleep(int usec)
 {
+    if (unlikely(usec < 0)) {
+        errno = EINVAL;
+        return -1;
+    }
+
     errno = EINTR;
     return 0;
 }
 
 static int _stat(char *file, struct stat *st)
 {
+    if (unlikely(!st)) {
+        errno = EFAULT;
+        return -1;
+    }
+
     st->st_mode = S_IFCHR;
     return 0;
 }
 
 static int _open(char *path, int flags)
 {
+    errno = ENOENT;
     return -1;
 }
 
 static int _close(int file)
 {
+    if (unlikely(file < 0)) {
+        errno = EBADF;
+        return -1;
+    }
     return -1;
 }
 
 static int _read(int file, char *ptr, int len)
 {
-    int idx;
+    if (unlikely(!ptr || len < 0)) {
+        errno = EFAULT;
+        return -1;
+    }
+
+    if (unlikely(file < 0)) {
+        errno = EBADF;
+        return -1;
+    }
 
+    int idx;
     for (idx = 0; idx < len; idx++)
         *ptr++ = _getchar();
 
@@ -126,8 +163,17 @@ static int _read(int file, char *ptr, int len)
 
 static int _write(int file, char *ptr, int len)
 {
-    int idx;
+    if (unlikely(!ptr || len < 0)) {
+        errno = EFAULT;
+        return -1;
+    }
+
+    if (unlikely(file < 0)) {
+        errno = EBADF;
+        return -1;
+    }
 
+    int idx;
     for (idx = 0; idx < len; idx++)
         _putchar(*ptr++);
 
@@ -136,37 +182,60 @@ static int _write(int file, char *ptr, int len)
 
 static int _lseek(int file, int ptr, int dir)
 {
+    if (unlikely(file < 0)) {
+        errno = EBADF;
+        return -1;
+    }
     return 0;
 }
 
 static int _chdir(const char *path)
 {
-    errno = EFAULT;
+    if (unlikely(!path)) {
+        errno = EFAULT;
+        return -1;
+    }
+    errno = ENOENT;
     return -1;
 }
 
 static int _mknod(const char *path, int mode, int dev)
 {
-    errno = EFAULT;
+    if (unlikely(!path)) {
+        errno = EFAULT;
+        return -1;
+    }
+    errno = EPERM;
     return -1;
 }
 
 static int _unlink(char *name)
 {
+    if (unlikely(!name)) {
+        errno = EFAULT;
+        return -1;
+    }
     errno = ENOENT;
     return -1;
 }
 
 static int _link(char *old, char *new)
 {
+    if (unlikely(!old || !new)) {
+        errno = EFAULT;
+        return -1;
+    }
     errno = EMLINK;
     return -1;
 }
 
 /* Linmo syscalls (wrapper implementation) */
 
-int _tadd(void *task, int stack_size)
+static int _tadd(void *task, int stack_size)
 {
+    if (unlikely(!task || stack_size <= 0))
+        return -EINVAL;
+
     return mo_task_spawn(task, stack_size);
 }
 
@@ -175,8 +244,11 @@ int sys_task_add(void *task, int stack_size)
     return syscall(SYS_tadd, task, (void *) stack_size, 0);
 }
 
-int _tcancel(int id)
+static int _tcancel(int id)
 {
+    if (unlikely(id <= 0))
+        return -EINVAL;
+
     return mo_task_cancel(id);
 }
 
@@ -185,36 +257,36 @@ int sys_task_cancel(int id)
     return syscall(SYS_tcancel, (void *) id, 0, 0);
 }
 
-int _tyield(void)
+static int _tyield(void)
 {
     mo_task_yield();
-
     return 0;
 }
 
 int sys_task_yield(void)
 {
-    syscall(SYS_tyield, 0, 0, 0);
-
-    return 0;
+    return syscall(SYS_tyield, 0, 0, 0);
 }
 
-int _tdelay(int ticks)
+static int _tdelay(int ticks)
 {
-    mo_task_delay(ticks);
+    if (unlikely(ticks < 0))
+        return -EINVAL;
 
+    mo_task_delay(ticks);
     return 0;
 }
 
 int sys_task_delay(int ticks)
 {
-    syscall(SYS_tdelay, (void *) ticks, 0, 0);
-
-    return 0;
+    return syscall(SYS_tdelay, (void *) ticks, 0, 0);
 }
 
-int _tsuspend(int id)
+static int _tsuspend(int id)
 {
+    if (unlikely(id <= 0))
+        return -EINVAL;
+
     return mo_task_suspend(id);
 }
 
@@ -223,8 +295,11 @@ int sys_task_suspend(int id)
     return syscall(SYS_tsuspend, (void *) id, 0, 0);
 }
 
-int _tresume(int id)
+static int _tresume(int id)
 {
+    if (unlikely(id <= 0))
+        return -EINVAL;
+
     return mo_task_resume(id);
 }
 
@@ -233,9 +308,11 @@ int sys_task_resume(int id)
     return syscall(SYS_tresume, (void *) id, 0, 0);
 }
 
-
-int _tpriority(int id, int priority)
+static int _tpriority(int id, int priority)
 {
+    if (unlikely(id <= 0))
+        return -EINVAL;
+
     return mo_task_priority(id, priority);
 }
 
@@ -244,7 +321,7 @@ int sys_task_priority(int id, int priority)
     return syscall(SYS_tpriority, (void *) id, (void *) priority, 0);
 }
 
-int _tid(void)
+static int _tid(void)
 {
     return mo_task_id();
 }
@@ -254,21 +331,18 @@ int sys_task_id(void)
     return syscall(SYS_tid, 0, 0, 0);
 }
 
-int _twfi(void)
+static int _twfi(void)
 {
     mo_task_wfi();
-
     return 0;
 }
 
 int sys_task_wfi(void)
 {
-    syscall(SYS_twfi, 0, 0, 0);
-
-    return 0;
+    return syscall(SYS_twfi, 0, 0, 0);
 }
 
-int _tcount(void)
+static int _tcount(void)
 {
     return mo_task_count();
 }
@@ -278,7 +352,7 @@ int sys_task_count(void)
     return syscall(SYS_tcount, 0, 0, 0);
 }
 
-int _ticks(void)
+static int _ticks(void)
 {
     return mo_ticks();
 }
@@ -288,7 +362,7 @@ int sys_ticks(void)
     return syscall(SYS_ticks, 0, 0, 0);
 }
 
-int _uptime(void)
+static int _uptime(void)
 {
     return mo_uptime();
 }