On Tue, Apr 14, 2020 at 01:01:09PM -0500, Josh Poimboeuf wrote:
> On Tue, Apr 14, 2020 at 07:44:06PM +0200, Peter Zijlstra wrote:
> > On Tue, Apr 14, 2020 at 11:28:37AM -0500, Josh Poimboeuf wrote:
> > > KLP relocations are livepatch-specific relocations which are applied to
> > > 1) vmlinux-specific KLP relocation sections
> > >
> > > .klp.rela.vmlinux.{sec}
> > >
> > > These are relocations (applied to the KLP module) which reference
> > > unexported vmlinux symbols.
> > >
> > > 2) module-specific KLP relocation sections
> > >
> > > .klp.rela.{module}.{sec}:
> > >
> > > These are relocations (applied to the KLP module) which reference
> > > unexported or exported module symbols.
> >
> > Is there something that disallows a module from being called 'vmlinux' ?
> > If not, we might want to enforce this somewhere.
>
> I'm pretty sure we don't have a check for that anywhere, though the KLP
> module would almost certainly fail during the module load when it
> couldn't find the vmlinux.ko symbols it needed.
>
> It wouldn't hurt to add a check somewhere though. Maybe in
> klp_module_coming() since the restriction only applies to
> CONFIG_LIVEPATCH...
From: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Subject: [PATCH] livepatch: Disallow vmlinux.ko
This is purely a theoretical issue, but if there were a module named
vmlinux.ko, the livepatch relocation code wouldn't be able to
distinguish between vmlinux-specific and vmlinux.o-specific KLP
relocations.
If CONFIG_LIVEPATCH is enabled, don't allow a module named vmlinux.ko.
Suggested-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
---
kernel/livepatch/core.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
index 3a88639b3326..3ff886b911ae 100644
--- a/kernel/livepatch/core.c
+++ b/kernel/livepatch/core.c
@@ -1169,6 +1169,11 @@ int klp_module_coming(struct module *mod)
if (WARN_ON(mod->state != MODULE_STATE_COMING))
return -EINVAL;
+ if (!strcmp(mod->name, "vmlinux")) {
+ pr_err("vmlinux.ko: invalid module name");
+ return -EINVAL;
+ }
+
mutex_lock(&klp_mutex);
/*
* Each module has to know that klp_module_coming()
--
2.21.1
