Re: Undoing module RONX protection fix
From: Jan Glauber
Date: Thu Apr 28 2011 - 06:08:28 EST
On Wed, 2011-04-27 at 14:42 +0930, Rusty Russell wrote:
> On Thu, 21 Apr 2011 16:19:49 +0200, Jan Glauber <jang@xxxxxxxxxxxxxxxxxx> wrote:
> > On Mon, Apr 18, 2011 at 08:13:36PM +0930, Rusty Russell wrote:
> > > On Mon, 18 Apr 2011 11:23:48 +0200, Jan Glauber <jang@xxxxxxxxxxxxxxxxxx> wrote:
> > > > While debugging I stumbled over two problems in the code that protects module
> > > > pages.
> > > >
> > > > First issue is that disabling the protection before freeing init or unload of
> > > > a module is not symmetric with the enablement. For instance, if pages are set
> > > > to RO the page range from module_core to module_core + core_ro_size is
> > > > protected. If a module is unloaded the page range from module_core to
> > > > module_core + core_size is set back to RW.
> > > > So pages that were not set to RO are also changed to RW.
> > > > This is not critical but IMHO it should be symmetric.
> > > >
> > > > Second issue is that while set_memory_rw & set_memory_ro are used for
> > > > RO/RW changes only set_memory_nx is involved for NX/X. One would await that
> > > > the inverse function is called when the NX protection should be removed,
> > > > which is not the case here, unless I'm missing something.
> > > >
> > > > The following patch addresses both issues. Works on s390. Boot tested on x86.
> > > >
> > > > Please comment,
> > >
> > > Applied, minus the S/390 EXPORT_SYMBOL which Christoph pointed out. I
> > > turned your mail into the commit message, since it was clearer and more
> > > verbose. I don't see why they would be different.
> >
> > There's a bug in my patch which just killed one of my s390 machines.
> > Can you merge this with the previuos patch?
>
> Hmm...
>
> Applied, but that function is really kind of silly. We should probably
> just split into unset_section_ro_nx() into unset_module_init_ro_nx() and
> unset_module_core_ro_nx().
>
> (And why isn't that function static anyway?)
>
> Patch appreciated :)
> Rusty.
How about this?
To be honest I don't like the inverse naming like in unset no-execute
too much, it makes me feel dizzy. But I wanted to keep the changes minimal.
Jan
------
Split the unprotect function into a function per section to make
the code more readable and add the missing static declaration.
Signed-off-by: Jan Glauber <jang@xxxxxxxxxxxxxxxxxx>
---
kernel/module.c | 47 ++++++++++++++++++++++++++---------------------
1 file changed, 26 insertions(+), 21 deletions(-)
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -1607,24 +1607,28 @@ static void set_section_ro_nx(void *base
}
}
-/* Setting memory back to W+X before releasing it */
-void unset_section_ro_nx(struct module *mod, void *module_region)
+static void unset_module_core_ro_nx(struct module *mod)
{
- if (mod->module_core && mod->module_core == module_region) {
- set_page_attributes(mod->module_core + mod->core_text_size,
- mod->module_core + mod->core_size,
- set_memory_x);
- set_page_attributes(mod->module_core,
- mod->module_core + mod->core_ro_size,
- set_memory_rw);
- } else if (mod->module_init && mod->module_init == module_region) {
- set_page_attributes(mod->module_init + mod->init_text_size,
- mod->module_init + mod->init_size,
- set_memory_x);
- set_page_attributes(mod->module_init,
- mod->module_init + mod->init_ro_size,
- set_memory_rw);
- }
+ if (mod->module_core == NULL)
+ return;
+ set_page_attributes(mod->module_core + mod->core_text_size,
+ mod->module_core + mod->core_size,
+ set_memory_x);
+ set_page_attributes(mod->module_core,
+ mod->module_core + mod->core_ro_size,
+ set_memory_rw);
+}
+
+static void unset_module_init_ro_nx(struct module *mod)
+{
+ if (mod->module_init == NULL)
+ return;
+ set_page_attributes(mod->module_init + mod->init_text_size,
+ mod->module_init + mod->init_size,
+ set_memory_x);
+ set_page_attributes(mod->module_init,
+ mod->module_init + mod->init_ro_size,
+ set_memory_rw);
}
/* Iterate through all modules and set each module's text as RW */
@@ -1670,7 +1674,8 @@ void set_all_modules_text_ro()
}
#else
static inline void set_section_ro_nx(void *base, unsigned long text_size, unsigned long ro_size, unsigned long total_size) { }
-static inline void unset_section_ro_nx(struct module *mod, void *module_region) { }
+static void unset_module_core_ro_nx(struct module *mod) { }
+static void unset_module_init_ro_nx(struct module *mod) { }
#endif
/* Free a module, remove from lists, etc. */
@@ -1697,7 +1702,7 @@ static void free_module(struct module *m
destroy_params(mod->kp, mod->num_kp);
/* This may be NULL, but that's OK */
- unset_section_ro_nx(mod, mod->module_init);
+ unset_module_init_ro_nx(mod);
module_free(mod, mod->module_init);
kfree(mod->args);
percpu_modfree(mod);
@@ -1706,7 +1711,7 @@ static void free_module(struct module *m
lockdep_free_key_range(mod->module_core, mod->core_size);
/* Finally, free the core (containing the module structure) */
- unset_section_ro_nx(mod, mod->module_core);
+ unset_module_core_ro_nx(mod);
module_free(mod, mod->module_core);
#ifdef CONFIG_MPU
@@ -2932,7 +2937,7 @@ SYSCALL_DEFINE3(init_module, void __user
mod->symtab = mod->core_symtab;
mod->strtab = mod->core_strtab;
#endif
- unset_section_ro_nx(mod, mod->module_init);
+ unset_module_init_ro_nx(mod);
module_free(mod, mod->module_init);
mod->module_init = NULL;
mod->init_size = 0;
--
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