mirror of
https://github.com/torvalds/linux.git
synced 2026-10-07 22:37:45 -04:00
Steven Rostedt (Red Hat)
70c8217acd
If a task uses a non constant string for the format parameter in trace_printk(), then the trace_printk_fmt variable is set to NULL. This variable is then saved in the __trace_printk_fmt section. The function hold_module_trace_bprintk_format() checks to see if duplicate formats are used by modules, and reuses them if so (saves them to the list if it is new). But this function calls lookup_format() that does a strcmp() to the value (which is now NULL) and can cause a kernel oops. This wasn't an issue till3debb0a9dd("tracing: Fix trace_printk() to print when not using bprintk()") which added "__used" to the trace_printk_fmt variable, and before that, the kernel simply optimized it out (no NULL value was saved). The fix is simply to handle the NULL pointer in lookup_format() and have the caller ignore the value if it was NULL. Link: http://lkml.kernel.org/r/[email protected] Reported-by: xingzhen <[email protected]> Acked-by: Namhyung Kim <[email protected]> Fixes:3debb0a9dd("tracing: Fix trace_printk() to print when not using bprintk()") Cc: [email protected] # v3.5+ Signed-off-by: Steven Rostedt <[email protected]>