Date: Fri, 16 Dec 2005 20:10:57 +1100 From: Peter Jeremy <PeterJeremy@optushome.com.au> To: "Wojciech A. Koszek" <dunstan@freebsd.czest.pl> Cc: freebsd-hackers@freebsd.org, phk@freebsd.org Subject: Re: [CALL FOR TESTERS] New system call: abort2() Message-ID: <20051216091057.GQ77268@cirb503493.alcatel.com.au> In-Reply-To: <20051215223745.GA37768@FreeBSD.czest.pl> References: <20051215223745.GA37768@FreeBSD.czest.pl>
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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
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