[CALL FOR TESTERS] New system call: abort2()

[Peter Jeremy]

On Thu, 2005-Dec-15 22:37:45 +0000, Wojciech A. Koszek wrote:
>	abort2(const char *why, int nargs, void **args);
>
>"why" is reason of program abort, "nargs" is number of arguments
>passed in "args". Both "why" and "args" (with "%p" format) will be
>printed via log(9). Sample output:
>[..]
>pid <3004> <abort2> abort2: ABORT2 <arg0:0x62612f2e>
>pid <3019> <abort2> abort2: invalid argument
>[..]

I don't believe the following code is correct.  uap->args is a
userspace pointer so uap->args[i] is dereferencing a userspace
argument in kernelspace.
+                       arg = uargs[i] = (void *) fuword(uap->args[i]);
I think it should be fuword(uap->args + i);

I don't see the point of the following test.  "arg" is printed using
%p and never de-referenced so there's no reason it can't be NULL.  I
would see that a legitimate use of abort2() is when the application
detects that a pointer is unexpectedly NULL.  Aborting on -1 is less
clear - if fuword() fails, it will return -1 but, equally, a faulty
user application may have left -1 in a pointer.  (Note that mmap(2)
returns -1 on error so it's not inconceivable that a pointer could
contain -1).

+                       /* Prevent from faults in user-space */
+                       if (arg == NULL || arg == (void *)-1) {
+                               error = EINVAL;
+                               break;
+                       }

Taking the above into account, I believe the code should be:
+               if (uap->args == NULL)
+                       break;
+               error = copyin(uap->args, uargs, uap->nargs * sizeof (void *));
+               if (error != 0)
+                       break;

-- 
Peter Jeremy