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SubjectRe: [UPDATED PATCH] fix memory corruption from misinterpreted bad_inode_ops return values
Andrew Morton wrote:
> On Thu, 04 Jan 2007 15:04:17 -0600
> Eric Sandeen <sandeen@redhat.com> wrote:
>
>> Andrew Morton wrote:
>>> On Thu, 4 Jan 2007 20:24:12 +0000
>>> Al Viro <viro@ftp.linux.org.uk> wrote:
>>>
>>>> So my main issue with fs/bad_inode.c is not even cast per se; it's that
>>>> cast is to void *.
>>> But Eric's latest patch is OK in that regard, isn't it? It might confuse
>>> parsers (in fixable ways), but it is type-correct and has no casts. (Well,
>>> it kinda has an link-time cast).
>> Even if it is, I'm starting to wonder if all this tricksiness is really
>> worth it for 400 bytes or so. :)
>>
>
> Ah, but it's a learning opportunity!

*grin*

> btw, couldn't we fix this bug with a simple old
>
> --- a/fs/bad_inode.c~a
> +++ a/fs/bad_inode.c
> @@ -15,7 +15,7 @@
> #include <linux/smp_lock.h>
> #include <linux/namei.h>
>
> -static int return_EIO(void)
> +static long return_EIO(void)
> {
> return -EIO;
> }
> _
>
> ?

What about ops that return loff_t (64 bits) on 32-bit arches and stuff
it into 2 registers....
#include <stdio.h>
#include <sys/types.h>
#include <sys/errno.h>

static long return_EIO(void)
{
return -EIO;
}
#define EIO_ERROR ((void *) (return_EIO))

int main(int argc, char ** argv)
{
loff_t error;
loff_t (*fn_ptr) (int);
fn_ptr = EIO_ERROR;

error = fn_ptr(0);
printf("and... error is %lld\n", error);
return 0;
}
[root]# ./ssize_eio
and... error is 8589934587
[root]# uname -m
i686

I'm still not convinced that this is the best place to be clever :)

-Eric
-
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