In the Linux kernel, the following vulnerability has been resolved:
ufs: core: tracing: Do not dereference pointers in TP_printk()
The trace events in drivers/ufs/core/ufs_trace.h were converted to take a pointer to the hba structure as an argument for the tracepoint and then in TP_printk() the printing of the dev_name from the ring buffer was converted to using the dev dereferenced pointer from the hba saved pointer.
This is not allowed as the TP_printk() is executed at the time the trace event is read from /sys/kernel/tracing/trace file. That can happen literally, seconds, minutes, hours, weeks, days, or even months later! There is no guarantee that the hba pointer will still exist by the time it is dereferenced when the "trace" file is read.
Instead, save the device name from the hba pointer at the time the tracepoint is called and place it into the ring buffer event. Then the TP_printk() can read the name directly from the ring buffer and remove the possibility that it will read a freed pointer and crash the kernel.
This was detected when testing the trace event code that looks for TP_printk() parameters doing illegal derferences[1]
[1] https://lore.kernel.org/all/[email protected]/