Re: [PATCH v2 0/3] tracing: Fix synthetic event bug

[Tom Zanussi]

Hi Steve,

On Wed, 2022-10-12 at 06:40 -0400, Steven Rostedt wrote:
> 
> The follow commands caused a crash:
> 
>   # cd /sys/kernel/tracing
>   # echo 's:open char file[]' > dynamic_events
>   # echo
> 'hist:keys=common_pid:file=filename:onchange($file).trace(open,$file)
> ' > events/syscalls/sys_enter_openat/trigger'
>   # echo 1 > events/synthetic/open/enable
> 
> BOOM!
> 
> The problem is that the synthetic event field "char file[]" will read
> the value given to it as a string without any memory checks to make
> sure
> the address is valid. The above example will pass in the user space
> address and the sythetic event code will happily call strlen() on it
> and then strscpy() where either one will cause an oops when accessing
> user space addresses.
> 
> Changes since v1:
> https://lore.kernel.org/all/20221011212501.773319898@xxxxxxxxxxx/
> 
>  - Handle "(fault)" printing when there's a fault


Thanks for fixing the synthetic event string tracing bug, along with
the other nice cleanup.

Reviewed-by: Tom Zanussi <zanussi@xxxxxxxxxx>



> 
> Steven Rostedt (Google) (3):
>       tracing: Move duplicate code of trace_kprobe/eprobe.c into
> header
>       tracing: Add "(fault)" name injection to kernel probes
>       tracing: Fix reading strings from synthetic events
> 
> ----
>  kernel/trace/trace_eprobe.c       |  60 ++------------------
>  kernel/trace/trace_events_synth.c |  23 ++++++--
>  kernel/trace/trace_kprobe.c       |  60 ++------------------
>  kernel/trace/trace_probe_kernel.h | 115
> ++++++++++++++++++++++++++++++++++++++
>  4 files changed, 142 insertions(+), 116 deletions(-)
>  create mode 100644 kernel/trace/trace_probe_kernel.h