Messages in this thread | | | Subject | Re: [Patch] kernel: bug fixing for kernel/kmod.c | From | Matt Helsley <> | Date | Wed, 02 Aug 2006 18:52:40 -0700 |
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On Wed, 2006-08-02 at 22:30 +0800, Kenneth Lee wrote: > I think there is a bug in kmod.c: In __call_usermodehelper(), when > kernel_thread(wait_for_helper, ...) return success, since > wait_for_helper() might call complete() at any time, the sub_info should > not be used any more. > > Normally wait_for_helper() take a long time to finish, you may not get > problem for most of the case. But if you remove /sbin/modprobe, it may > become easier for you to get a oop in khelper. > > the following patch is made in 2.6.17.7 > > --- linux-2.6.17.7/kernel/kmod.c.orig 2006-08-02 22:13:21.805902750 > +0800 > +++ linux-2.6.17.7/kernel/kmod.c 2006-08-02 22:15:36.946348500 > +0800 > @@ -198,6 +198,7 @@ static void __call_usermodehelper(void * > { > struct subprocess_info *sub_info = data; > pid_t pid; > + int wait = sub_info->wait; > > /* CLONE_VFORK: wait until the usermode helper has execve'd > * successfully We need the data structures to stay around > @@ -212,7 +213,7 @@ static void __call_usermodehelper(void * > if (pid < 0) { > sub_info->retval = pid; > complete(sub_info->complete); > - } else if (!sub_info->wait) > + } else if (!wait) > complete(sub_info->complete); > } >
Looks like a correct fix for the race to me. I think you'd make the code slightly easier to read by replacing the initial test too:
if (sub_info->wait) pid = kernel_thread(...
with:
if (wait) pid = kernel_thread(...
Cheers, -Matt Helsley
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