Date: Fri, 16 Dec 2005 21:50:02 +0000 From: "Wojciech A. Koszek" <dunstan@freebsd.czest.pl> To: Peter Jeremy <PeterJeremy@optushome.com.au> Cc: freebsd-hackers@freebsd.org, phk@freebsd.org Subject: Re: [CALL FOR TESTERS] New system call: abort2() Message-ID: <20051216215002.GA58739@FreeBSD.czest.pl> In-Reply-To: <20051216091057.GQ77268@cirb503493.alcatel.com.au> References: <20051215223745.GA37768@FreeBSD.czest.pl> <20051216091057.GQ77268@cirb503493.alcatel.com.au>
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On Fri, Dec 16, 2005 at 08:10:57PM +1100, Peter Jeremy wrote: > 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; Of course! Thanks for this comment! Updated version should be available soon. -- * Wojciech A. Koszek && dunstan@FreeBSD.czest.pl
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