Messages in this thread | | | Date | Mon, 26 Sep 2022 14:38:28 +0800 (GMT+08:00) | From | duoming@zju ... | Subject | Re: [PATCH V9] devcoredump: add context check in dev_coredumpm |
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Hello,
On Mon, 26 Sep 2022 08:27:58 +0200 Greg KH wrote:
> On Mon, Sep 26, 2022 at 02:16:09PM +0800, Duoming Zhou wrote: > > The dev_coredumpm(), dev_coredumpv() and dev_coredumpsg() could not > > be used in atomic context, because they call kvasprintf_const() and > > kstrdup() with GFP_KERNEL parameter. The process is shown below: > > > > dev_coredumpv(.., gfp_t gfp) > > dev_coredumpm(.., gfp_t gfp) > > dev_set_name > > kobject_set_name_vargs > > kvasprintf_const(GFP_KERNEL, ...); //may sleep > > kstrdup(s, GFP_KERNEL); //may sleep > > > > This patch adds context check in dev_coredumpm() in order to show > > dev_coredumpm() and its callers could not be used in atomic context. > > > > What's more, this change can allow the api to evolve and will not > > influence the users that call this api. > > > > Fixes: 833c95456a70 ("device coredump: add new device coredump class") > > Signed-off-by: Duoming Zhou <duoming@zju.edu.cn> > > --- > > Changes in v9: > > - Add context check in dev_coredumpm(). > > > > drivers/base/devcoredump.c | 3 +++ > > 1 file changed, 3 insertions(+) > > > > diff --git a/drivers/base/devcoredump.c b/drivers/base/devcoredump.c > > index f4d794d6bb8..806ee872f5f 100644 > > --- a/drivers/base/devcoredump.c > > +++ b/drivers/base/devcoredump.c > > @@ -255,6 +255,9 @@ void dev_coredumpm(struct device *dev, struct module *owner, > > struct devcd_entry *devcd; > > struct device *existing; > > > > + if (!gfpflags_normal_context(gfp)) > > + goto free; > > Wait, this just broke things for no good reason if a caller happened to > have set a GFP flag that we do not like at the moment. > > What code now does not work that previously did work with this change?
I found that all users in the kernel call the dev_coredumpv(), dev_coredumpm() and dev_coredumpsg() with "GFP_KERNEL". So this change will not influence the existing users.
Best regards, Duoming Zhou | |