Messages in this thread | | | Date | Sat, 4 Sep 2021 08:32:09 +0200 | From | Greg Kroah-Hartman <> | Subject | Re: [PATCH] char: misc: init list head only when needed |
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On Mon, Aug 16, 2021 at 06:12:32PM +0800, Jiazi Li wrote: > If a module successfully registers a misc device. > Then, due to some bugs, use same address register misc device > again, init list head will corrupt misc_list, resulting in oops > when using misc_list.
Then fix those bugs that try to register the misc device more than once?
Does that happen in any in-kernel drivers or is this just a failure of external drivers that are not submitted to the kernel tree?
> In this scenario, do not init list head, if registration is > successful, init list head is also not required. > > Signed-off-by: Jiazi Li <lijiazi@xiaomi.com> > --- > drivers/char/misc.c | 19 ++++++++++++++----- > 1 file changed, 14 insertions(+), 5 deletions(-) > > diff --git a/drivers/char/misc.c b/drivers/char/misc.c > index ca5141e..2451640 100644 > --- a/drivers/char/misc.c > +++ b/drivers/char/misc.c > @@ -176,7 +176,6 @@ int misc_register(struct miscdevice *misc) > int err = 0; > bool is_dynamic = (misc->minor == MISC_DYNAMIC_MINOR); > > - INIT_LIST_HEAD(&misc->list); > > mutex_lock(&misc_mtx); > > @@ -185,7 +184,7 @@ int misc_register(struct miscdevice *misc) > > if (i >= DYNAMIC_MINORS) { > err = -EBUSY; > - goto out; > + goto err2; > } > misc->minor = DYNAMIC_MINORS - i - 1; > set_bit(i, misc_minors); > @@ -195,7 +194,13 @@ int misc_register(struct miscdevice *misc) > list_for_each_entry(c, &misc_list, list) { > if (c->minor == misc->minor) { > err = -EBUSY; > - goto out; > + /* > + * if module use same address double register, > + * init list will corrupt misc_list
I do not understand the text here at all, sorry.
thanks,
greg k-h
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