Messages in this thread Patch in this message |  | | | Date | Wed, 14 Dec 2005 09:40:27 +0530 | | From | Ashutosh Naik <> | | Subject | Re: [RFC][PATCH] Prevent overriding of Symbols in the Kernel, avoiding Undefined behaviour |
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On 12/14/05, Rusty Russell <rusty@rustcorp.com.au> wrote:
> Patch looks good! A few nits still:
Have resolved all the nits ( hopefully :) )
> We already do this to resolve (more) symbols, so I don't see it as a > problem. However, I believe that lock is redundant here: we need both > locks to write the list, but either is sufficient for reading, and we > already hold the sem.
Ya, the lock is redundant here, as we are already inside a semaphore.
Signed-off-by: Ashutosh Naik <ashutosh.naik@gmail.com> Signed-off-by: Anand Krishnan <anandhkrishnan@yahoo.co.in>
--- linux-2.6.15-rc5/kernel/module.c.orig 2005-12-14 09:27:53.000000000 +0530 +++ linux-2.6.15-rc5/kernel/module.c 2005-12-14 09:18:31.000000000 +0530 @@ -1204,6 +1204,39 @@ void *__symbol_get(const char *symbol) } EXPORT_SYMBOL_GPL(__symbol_get);
+/* + * Ensure that an exported symbol [global namespace] does not already exist + * in the Kernel or in some other modules exported symbol table. + */ +static int verify_export_symbols(struct module *mod) +{ + const char *name = NULL; + unsigned long i, ret = 0; + struct module *owner; + const unsigned long *crc; + + for (i = 0; i < mod->num_syms; i++) + if (!__find_symbol(mod->syms[i].name, &owner, &crc, 1)) { + name = mod->syms[i].name; + ret = -ENOEXEC; + goto dup; + } + + for (i = 0; i < mod->num_gpl_syms; i++) + if (!__find_symbol(mod->gpl_syms[i].name, &owner, &crc, 1)) { + name = mod->gpl_syms[i].name; + ret = -ENOEXEC; + goto dup; + } + +dup: + if (ret) + printk(KERN_ERR "%s: exports duplicate symbol %s (owned by %s)\n", + mod->name, name, module_name(owner)); + + return ret; +} + /* Change all symbols so that sh_value encodes the pointer directly. */ static int simplify_symbols(Elf_Shdr *sechdrs, unsigned int symindex, @@ -1767,6 +1800,12 @@ static struct module *load_module(void _ goto cleanup; }
+ /* Find duplicate symbols */ + err = verify_export_symbols(mod); + + if (err < 0) + goto cleanup; + /* Set up and sort exception table */ mod->num_exentries = sechdrs[exindex].sh_size / sizeof(*mod->extable); mod->extable = extable = (void *)sechdrs[exindex].sh_addr; - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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