On Tue, 2 Jun 2015, Minfei Huang wrote:
> On Mon, Jun 1, 2015 at 11:48 PM, Miroslav Benes <mbenes@xxxxxxx> wrote:
> > The list of loaded modules is walked through in
> > module_kallsyms_on_each_symbol (called by kallsyms_on_each_symbol). The
> > module_mutex lock should be acquired to prevent potential corruptions
> > in the list.
> >
> > This was uncovered with new lockdep asserts in module code introduced by
> > the commit 0be964be0d45 ("module: Sanitize RCU usage and locking") in
> > recent next- trees.
> >
> > Signed-off-by: Miroslav Benes <mbenes@xxxxxxx>
> > ---
> > kernel/livepatch/core.c | 18 +++++++++++++-----
> > 1 file changed, 13 insertions(+), 5 deletions(-)
> >
> > diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
> > index e6c8d54..c40ebcc 100644
> > --- a/kernel/livepatch/core.c
> > +++ b/kernel/livepatch/core.c
> > @@ -179,7 +179,9 @@ static int klp_find_object_symbol(const char *objname, const char *name,
> > .count = 0
> > };
> >
> > + mutex_lock(&module_mutex);
> > kallsyms_on_each_symbol(klp_find_callback, &args);
> > + mutex_unlock(&module_mutex);
> >
> > if (args.count == 0)
> > pr_err("symbol '%s' not found in symbol table\n", name);
> > @@ -219,13 +221,19 @@ static int klp_verify_vmlinux_symbol(const char *name, unsigned long addr)
> > .name = name,
> > .addr = addr,
> > };
> > + int ret;
> >
> > - if (kallsyms_on_each_symbol(klp_verify_callback, &args))
> > - return 0;
> > + mutex_lock(&module_mutex);
> > + ret = kallsyms_on_each_symbol(klp_verify_callback, &args);
> > + mutex_unlock(&module_mutex);
> >
>
> Hi.
> In livepatch code path, returning value 0 may represent the right, but
> sometime represent wrong, like the above function.
>
> Is it possible that we can wrap such function and return the unified
> value? Thus we can not confuse the returning value any more.
Hi,
I must admit I do not understand. Both klp_find_object_symbol and
klp_verify_vmlinux_symbol return 0 on success or -EINVAL. It is true that
kallsyms_on_each_symbol and module_kallsyms_on_each symbol are different.
That is why our kallsyms callbacks are different. See the implementation
of those. But that is the API. Is this what you are worried about?
> Otherwise annotation is appreciate.
Thanks,
Miroslav
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