On Tue, Dec 16, 2008 at 10:42:08AM -0800, Jesse Barnes wrote: > On Wednesday, December 10, 2008 11:43 am Neil Horman wrote: > > Hey- > > I happened to notice that the ibmphp hotplug driver does something > > rather silly in its init routine. It purposely calls module_put so as to > > underflow its module ref count to avoid being removed from the kernel. > > This is bad practice, and wrong, since it provides a window for subsequent > > module_gets to reset the refcount to zero, allowing an unload to race in > > and cause all sorts of mysterious panics. If the module is unsafe to load, > > it should inform the kernel as such with a call to __unsafe. The patch > > below does that. > > Thanks Neil, applied this to my for-linus branch since it sounds potentially > serious (but also low risk since who uses ibmphp anymore? :) > Dang it! Sorry, Jesse. Yes, youre absolutely right, it is low risk. It really just a bit of sillyness all around. Unfortunately, I took part in the sillyness. The problem was reported to me on RHEL, and I tested there, without checking upstream too closely. As aresult, the patch I gave you is a bit out of date, and won't compile. I've tested the new patch here much more closely. apologies. I informed akpm who was looking at it, but neglected to copy you. This patch corrects the same problem in that it prevents module unloads in a sane fashion, by not registering an exit routine Signed-off-by: Neil Horman <nhorman@xxxxxxxxxxxxx> ibmphp_core.c | 5 ----- 1 file changed, 5 deletions(-) diff --git a/drivers/pci/hotplug/ibmphp_core.c b/drivers/pci/hotplug/ibmphp_core.c index c892daa..633e743 100644 --- a/drivers/pci/hotplug/ibmphp_core.c +++ b/drivers/pci/hotplug/ibmphp_core.c @@ -1402,10 +1402,6 @@ static int __init ibmphp_init(void) goto error; } - /* lock ourselves into memory with a module - * count of -1 so that no one can unload us. */ - module_put(THIS_MODULE); - exit: return rc; @@ -1423,4 +1419,3 @@ static void __exit ibmphp_exit(void) } module_init(ibmphp_init); -module_exit(ibmphp_exit); > Jesse > -- /**************************************************** * Neil Horman <nhorman@xxxxxxxxxxxxx> * Software Engineer, Red Hat ****************************************************/ -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
