| Message ID | 20220705094946.827697-1-hsinyi@chromium.org |
|---|---|
| State | Accepted |
| Commit | 37101d3c719386040ded735a5ec06974f1d94d1f |
| Headers | show |
| Series | PM: domains: Ensure genpd_debugfs_dir exists before remove | expand |
On Tue, Jul 5, 2022 at 6:38 PM Greg Kroah-Hartman <gregkh@linuxfoundation.org> wrote: > > On Tue, Jul 05, 2022 at 05:49:47PM +0800, Hsin-Yi Wang wrote: > > genpd_debug_remove() may be indirectly called from others while > > genpd_debugfs_dir is not yet set. Make sure genpd_debugfs_dir exists > > before remove the sub components, otherwise components under > > /sys/kernel/debug may be accidentally removed. > > > > Fixes: 718072ceb211 ("PM: domains: create debugfs nodes when adding power domains") > > Signed-off-by: Hsin-Yi Wang <hsinyi@chromium.org> > > --- > > An example: > > scpsys_probe() in drivers/soc/mediatek/mtk-pm-domains.c indirectly calls > > genpd_debug_remove() on probe fail, causing /sys/kernel/debug/usb to be > > removed. > > --- > > drivers/base/power/domain.c | 3 +++ > > 1 file changed, 3 insertions(+) > > > > diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c > > index 3e86772d5fac5..5a2e0232862e0 100644 > > --- a/drivers/base/power/domain.c > > +++ b/drivers/base/power/domain.c > > @@ -222,6 +222,9 @@ static void genpd_debug_remove(struct generic_pm_domain *genpd) > > { > > struct dentry *d; > > > > + if (!genpd_debugfs_dir) > > + return; > > + > > d = debugfs_lookup(genpd->name, genpd_debugfs_dir); > > debugfs_remove(d); > > Why not just change this to be: > debugfs_remove(debugfs_lookup(genpd->name, debugfs_lookup("pm_genpd", NULL))); If pm_genpd hasn't been created yet, debugfs_lookup("pm_genpd", NULL) will return null. If genpd->name also exists under root debugfs, it will still be deleted unintentionally, since NULL represents root debugfs. Eg. one of the genpd->name is "usb", which is supposed to be added as /sys/kernel/debug/pm_genpd/usb later. But pm_genpd is not yet created, /sys/kernel/debug/usb will be removed. > > thanks, > > greg k-h
On Wed, Jul 6, 2022 at 12:26 AM Greg Kroah-Hartman <gregkh@linuxfoundation.org> wrote: > > On Tue, Jul 05, 2022 at 11:58:52PM +0800, Hsin-Yi Wang wrote: > > On Tue, Jul 5, 2022 at 7:51 PM Greg Kroah-Hartman > > <gregkh@linuxfoundation.org> wrote: > > > > > > On Tue, Jul 05, 2022 at 07:06:41PM +0800, Hsin-Yi Wang wrote: > > > > On Tue, Jul 5, 2022 at 6:38 PM Greg Kroah-Hartman > > > > <gregkh@linuxfoundation.org> wrote: > > > > > > > > > > On Tue, Jul 05, 2022 at 05:49:47PM +0800, Hsin-Yi Wang wrote: > > > > > > genpd_debug_remove() may be indirectly called from others while > > > > > > genpd_debugfs_dir is not yet set. Make sure genpd_debugfs_dir exists > > > > > > before remove the sub components, otherwise components under > > > > > > /sys/kernel/debug may be accidentally removed. > > > > > > > > > > > > Fixes: 718072ceb211 ("PM: domains: create debugfs nodes when adding power domains") > > > > > > Signed-off-by: Hsin-Yi Wang <hsinyi@chromium.org> > > > > > > --- > > > > > > An example: > > > > > > scpsys_probe() in drivers/soc/mediatek/mtk-pm-domains.c indirectly calls > > > > > > genpd_debug_remove() on probe fail, causing /sys/kernel/debug/usb to be > > > > > > removed. > > > > > > --- > > > > > > drivers/base/power/domain.c | 3 +++ > > > > > > 1 file changed, 3 insertions(+) > > > > > > > > > > > > diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c > > > > > > index 3e86772d5fac5..5a2e0232862e0 100644 > > > > > > --- a/drivers/base/power/domain.c > > > > > > +++ b/drivers/base/power/domain.c > > > > > > @@ -222,6 +222,9 @@ static void genpd_debug_remove(struct generic_pm_domain *genpd) > > > > > > { > > > > > > struct dentry *d; > > > > > > > > > > > > + if (!genpd_debugfs_dir) > > > > > > + return; > > > > > > + > > > > > > d = debugfs_lookup(genpd->name, genpd_debugfs_dir); > > > > > > debugfs_remove(d); > > > > > > > > > > Why not just change this to be: > > > > > debugfs_remove(debugfs_lookup(genpd->name, debugfs_lookup("pm_genpd", NULL))); > > > > If pm_genpd hasn't been created yet, debugfs_lookup("pm_genpd", NULL) > > > > will return null. > > > > > > And how is this codepath being called if pm_genpd is not created yet? > > > Surely you are not relying on the presence of a debugfs file to > > > determine that? > > > > > > > Caller didn't directly call genpd_debug_remove(). The flow is as follows: > > > > Normally, scpsys will create pm domain by: > > scpsys_probe() > > --> scpsys_add_one_domain() > > --> pm_genpd_init() > > --> genpd_debug_add() > > > > > > If something fails, it will do the cleanup: > > scpsys_probe() > > --> scpsys_domain_cleanup() > > --> scpsys_remove_one_domain() > > --> pm_genpd_remove() > > --> genpd_remove() > > --> genpd_debug_remove() > > > > genpd_debug_add() checks if genpd_debugfs_dir is init by a > > late_initcall genpd_debug_init(). If it's NULL, it will return > > directly without creating anything. Later when genpd_debug_init() is > > called, it will call genpd_debug_add() again. > > > > pm_genpd_remove() still needs to be called on the cleanup path to free > > other stuff, but if genpd_debug_init() hasn't happened, > > genpd_debug_remove() should be a no-op, or genpd_remove() shouldn't > > call it. (We can move the check there, but adding in > > genpd_debug_remove() is more similar to what genpd_debug_add() > > currently is.) > > Thanks for the details. You might want to include this in the changelog > text. I'm ok with the change now if that information is in there, I > missed that there are paths to create devices before debugfs is > initialized. > Done. Added in v2. Thanks for the review. > thanks, > > greg k-h
diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c index 3e86772d5fac5..5a2e0232862e0 100644 --- a/drivers/base/power/domain.c +++ b/drivers/base/power/domain.c @@ -222,6 +222,9 @@ static void genpd_debug_remove(struct generic_pm_domain *genpd) { struct dentry *d; + if (!genpd_debugfs_dir) + return; + d = debugfs_lookup(genpd->name, genpd_debugfs_dir); debugfs_remove(d); }
genpd_debug_remove() may be indirectly called from others while genpd_debugfs_dir is not yet set. Make sure genpd_debugfs_dir exists before remove the sub components, otherwise components under /sys/kernel/debug may be accidentally removed. Fixes: 718072ceb211 ("PM: domains: create debugfs nodes when adding power domains") Signed-off-by: Hsin-Yi Wang <hsinyi@chromium.org> --- An example: scpsys_probe() in drivers/soc/mediatek/mtk-pm-domains.c indirectly calls genpd_debug_remove() on probe fail, causing /sys/kernel/debug/usb to be removed. --- drivers/base/power/domain.c | 3 +++ 1 file changed, 3 insertions(+)