On Sat, Sep 30, 2023 at 05:46:56PM +0000, Joel Fernandes (Google) wrote: > From: Catalin Marinas <catalin.marinas@xxxxxxx> > > Since the actual slab freeing is deferred when calling kvfree_rcu(), so > is the kmemleak_free() callback informing kmemleak of the object > deletion. From the perspective of the kvfree_rcu() caller, the object is > freed and it may remove any references to it. Since kmemleak does not > scan RCU internal data storing the pointer, it will report such objects > as leaks during the grace period. > > Tell kmemleak to ignore such objects on the kvfree_call_rcu() path. Note > that the tiny RCU implementation does not have such issue since the > objects can be tracked from the rcu_ctrlblk structure. > > Signed-off-by: Catalin Marinas <catalin.marinas@xxxxxxx> > Reported-by: Christoph Paasch <cpaasch@xxxxxxxxx> > Closes: https://lore.kernel.org/all/F903A825-F05F-4B77-A2B5-7356282FBA2C@xxxxxxxxx/ > Cc: <stable@xxxxxxxxxxxxxxx> > Tested-by: Christoph Paasch <cpaasch@xxxxxxxxx> > Signed-off-by: Joel Fernandes (Google) <joel@xxxxxxxxxxxxxxxxx> Reviewed-by: Paul E. McKenney <paulmck@xxxxxxxxxx> > --- > kernel/rcu/tree.c | 9 +++++++++ > 1 file changed, 9 insertions(+) > > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c > index cb1caefa8bd0..24423877962c 100644 > --- a/kernel/rcu/tree.c > +++ b/kernel/rcu/tree.c > @@ -31,6 +31,7 @@ > #include <linux/bitops.h> > #include <linux/export.h> > #include <linux/completion.h> > +#include <linux/kmemleak.h> > #include <linux/moduleparam.h> > #include <linux/panic.h> > #include <linux/panic_notifier.h> > @@ -3388,6 +3389,14 @@ void kvfree_call_rcu(struct rcu_head *head, void *ptr) > success = true; > } > > + /* > + * The kvfree_rcu() caller considers the pointer freed at this point > + * and likely removes any references to it. Since the actual slab > + * freeing (and kmemleak_free()) is deferred, tell kmemleak to ignore > + * this object (no scanning or false positives reporting). > + */ > + kmemleak_ignore(ptr); > + > // Set timer to drain after KFREE_DRAIN_JIFFIES. > if (rcu_scheduler_active == RCU_SCHEDULER_RUNNING) > schedule_delayed_monitor_work(krcp); > -- > 2.42.0.582.g8ccd20d70d-goog >
