Re: Prevent overriding of Symbols in the Kernel, avoiding Undefined behaviour

[Ashutosh Naik]

On 12/13/05, Ashutosh Naik <ashutosh.naik@xxxxxxxxx> wrote:
> On 12/13/05, Rusty Russell <rusty@xxxxxxxxxxxxxxx> wrote:
> >
> > How about something like:
> >
> >         const struct kernel_symbol *sym;
> >         unsigned int i;
> >         const unsigned long *crc;
> >         struct module *owner;
> >
> >         spin_lock_irq(&modlist_lock);
> >         for (i = 0; i < mod->num_syms; i++)
> >                 if (__find_symbol(mod->syms[i].name, &owner, &crc, 1))
> >                         goto dup;
> >         for (i = 0; i < num->num_gpl_syms; i++)
> >                 if (__find_symbol(mod->gpl_syms[i].name,&owner,&crc,1))
> >                         goto dup;
> >         spin_unlock_irq(&modlist_lock);
> >         return 0;
> > dup:
> >         printk("%s: exports duplicate symbol (owned by %s)\n",
> >                 mod->name, module_name(owner));
> >         return -ENOEXEC;
> > }
>
> Have tried that in the attached patch. However,  mod->syms[i].name
> would be valid only after a long relocation for loop has run through.
> While this adds a wee bit extra overhead, that overhead is only in the
> case where the module does actually export a Duplicate Symbol.

Forgot to add
Signed-off-by: Ashutosh Naik <ashutosh.naik@xxxxxxxxx>
Signed-off-by: Anand Krishnan <anandhkrishnan@xxxxxxxxxxx>

Cheers
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