Support backports for stable version. There are two places where null
deref could happen before
commit 2c92ca849fcc ("tracing/treewide: Remove second parameter of 
__assign_str()")
Link: 
https://lore.kernel.org/linux-trace-kernel/20240516133454.681ba...@rorschach.local.home/

I've checked +v6.1.82 +v6.6.22 +v6.7.10, +v6.8, +6.9, this version need
to be applied, So, I applied the patch, tested it again, and confirmed
working fine.

Fixes: 51270d573a8d ("tracing/net_sched: Fix tracepoints that save qdisc_dev() 
as a string")
Link: https://lore.kernel.org/lkml/20240229143432.273b4...@gandalf.local.home/t/
Cc: net...@vger.kernel.org
Cc: sta...@vger.kernel.org # +v6.1.82 +v6.6.22 +v6.7.10, +v6.8, +6.9
Tested-by: Yunseong Kim <ysk...@gmail.com>
Reviewed-by: Pedro Tammela <pctamm...@mojatatu.com>
Signed-off-by: Yunseong Kim <ysk...@gmail.com>
Signed-off-by: Yeoreum Yun <yeoreum....@arm.com>
Link: https://lore.kernel.org/r/20240624173320.24945-4-ysk...@gmail.com
Signed-off-by: Paolo Abeni <pab...@redhat.com>
Signed-off-by: Sasha Levin <sas...@kernel.org>
---
 include/trace/events/qdisc.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/trace/events/qdisc.h b/include/trace/events/qdisc.h
index 1f4258308b96..061fd4960303 100644
--- a/include/trace/events/qdisc.h
+++ b/include/trace/events/qdisc.h
@@ -81,14 +81,14 @@ TRACE_EVENT(qdisc_reset,
        TP_ARGS(q),
 
        TP_STRUCT__entry(
-               __string(       dev,            qdisc_dev(q)->name      )
+               __string(       dev,            qdisc_dev(q) ? 
qdisc_dev(q)->name : "(null)"    )
                __string(       kind,           q->ops->id              )
                __field(        u32,            parent                  )
                __field(        u32,            handle                  )
        ),
 
        TP_fast_assign(
-               __assign_str(dev, qdisc_dev(q)->name);
+               __assign_str(dev, qdisc_dev(q) ? qdisc_dev(q)->name : "(null)");
                __assign_str(kind, q->ops->id);
                __entry->parent = q->parent;
                __entry->handle = q->handle;
-- 
2.45.2


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