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Date: Tue, 10 May 2011 10:30:45 -0400
From: Jason Baron <jbaron@...hat.com>
To: Jiri Olsa <jolsa@...hat.com>
Cc: rostedt@...dmis.org, mingo@...e.hu, linux-kernel@...r.kernel.org
Subject: Re: [PATCHv2] jump_label: check entries limit in __jump_label_update
On Tue, May 10, 2011 at 12:43:46PM +0200, Jiri Olsa wrote:
> On Mon, May 09, 2011 at 03:32:48PM -0400, Jason Baron wrote:
> > On Wed, May 04, 2011 at 05:30:23PM +0200, Jiri Olsa wrote:
> > > When iterating the jump_label entries array (core or modules),
> > > the __jump_label_update function peeks over the last entry.
> > >
> > > The reason is that the end of the for loop depends on the key
> > > value of the processed entry. Thus when going through the
> > > last array entry, we will touch the memory behind the array
> > > limit.
> > >
> > > This bug probably will never be triggered, since most likely the
> > > memory behind the jump_label entries will be accesable and the
> > > entry->key will be different than the expected value.
> > >
> > >
> > > Signed-off-by: Jiri Olsa <jolsa@...hat.com>
> > > ---
> > > kernel/jump_label.c | 17 ++++++++++++-----
> > > 1 files changed, 12 insertions(+), 5 deletions(-)
> > >
> > > diff --git a/kernel/jump_label.c b/kernel/jump_label.c
> > > index 74d1c09..b2ee97a 100644
> > > --- a/kernel/jump_label.c
> > > +++ b/kernel/jump_label.c
> > > @@ -105,9 +105,12 @@ static int __jump_label_text_reserved(struct jump_entry *iter_start,
> > > }
> > >
> > > static void __jump_label_update(struct jump_label_key *key,
> > > - struct jump_entry *entry, int enable)
> > > + struct jump_entry *entry,
> > > + struct jump_entry *stop, int enable)
> > > {
> > > - for (; entry->key == (jump_label_t)(unsigned long)key; entry++) {
> > > + for (; (entry < stop) &&
> > > + (entry->key == (jump_label_t)(unsigned long)key);
> > > + entry++) {
> > > /*
> > > * entry->code set to 0 invalidates module init text sections
> > > * kernel_text_address() verifies we are not in core kernel
> > > @@ -158,6 +161,7 @@ early_initcall(jump_label_init);
> > > struct jump_label_mod {
> > > struct jump_label_mod *next;
> > > struct jump_entry *entries;
> > > + struct jump_entry *entries_stop;
> > > struct module *mod;
> > > };
> > >
> > > @@ -181,7 +185,8 @@ static void __jump_label_mod_update(struct jump_label_key *key, int enable)
> > > struct jump_label_mod *mod = key->next;
> > >
> > > while (mod) {
> > > - __jump_label_update(key, mod->entries, enable);
> > > + __jump_label_update(key, mod->entries, mod->entries_stop,
> > > + enable);
> > > mod = mod->next;
> >
> > hmmm. Instead of adding a new field to the 'struct jump_label_mod' data
> > structure (and thus increasing its footprint), why not use:
> > mod->jump_entries + mod->num_jump_entries here?
>
> yep, overlooked the struct module pointer inside jump_label_mod
> attaching new patch
>
> thanks,
> jirka
>
> ---
> When iterating the jump_label entries array (core or modules),
> the __jump_label_update function peeks over the last entry.
>
> The reason is that the end of the for loop depends on the key
> value of the processed entry. Thus when going through the
> last array entry, we will touch the memory behind the array
> limit.
>
> This bug probably will never be triggered, since most likely the
> memory behind the jump_label entries will be accesable and the
> entry->key will be different than the expected value.
>
>
> Signed-off-by: Jiri Olsa <jolsa@...hat.com>
> ---
> kernel/jump_label.c | 18 +++++++++++++-----
> 1 files changed, 13 insertions(+), 5 deletions(-)
>
> diff --git a/kernel/jump_label.c b/kernel/jump_label.c
> index 74d1c09..fa27e75 100644
> --- a/kernel/jump_label.c
> +++ b/kernel/jump_label.c
> @@ -105,9 +105,12 @@ static int __jump_label_text_reserved(struct jump_entry *iter_start,
> }
>
> static void __jump_label_update(struct jump_label_key *key,
> - struct jump_entry *entry, int enable)
> + struct jump_entry *entry,
> + struct jump_entry *stop, int enable)
> {
> - for (; entry->key == (jump_label_t)(unsigned long)key; entry++) {
> + for (; (entry < stop) &&
> + (entry->key == (jump_label_t)(unsigned long)key);
> + entry++) {
> /*
> * entry->code set to 0 invalidates module init text sections
> * kernel_text_address() verifies we are not in core kernel
> @@ -181,7 +184,11 @@ static void __jump_label_mod_update(struct jump_label_key *key, int enable)
> struct jump_label_mod *mod = key->next;
>
> while (mod) {
> - __jump_label_update(key, mod->entries, enable);
> + struct module *m = mod->mod;
> +
> + __jump_label_update(key, mod->entries,
> + m->jump_entries + m->num_jump_entries,
> + enable);
> mod = mod->next;
> }
> }
> @@ -245,7 +252,8 @@ static int jump_label_add_module(struct module *mod)
> key->next = jlm;
>
> if (jump_label_enabled(key))
> - __jump_label_update(key, iter, JUMP_LABEL_ENABLE);
> + __jump_label_update(key, iter, iter_stop,
> + JUMP_LABEL_ENABLE);
> }
>
> return 0;
> @@ -371,7 +379,7 @@ static void jump_label_update(struct jump_label_key *key, int enable)
>
> /* if there are no users, entry can be NULL */
> if (entry)
> - __jump_label_update(key, entry, enable);
> + __jump_label_update(key, entry, __stop___jump_table, enable);
>
> #ifdef CONFIG_MODULES
> __jump_label_mod_update(key, enable);
> --
> 1.7.1
>
Looks good.
Acked-by: Jason Baron <jbaron@...hat.com>
Thanks,
-Jason
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