Re: [PATCH 5.15,6.1] Fixup preempt imbalance with bpf_trace_printk

[Greg KH <gregkh@linuxfoundation.org>]

On Sat, Feb 17, 2024 at 09:13:14AM -0300, Thadeu Lima de Souza Cascardo wrote:
> When bpf_trace_printk is called without any args in a second depth level,
> it will enable preemption without disabling it.
> 
> These patch series fix this for 5.15 and 6.1. The fix was introduced in
> 6.3, so later kernels already have it. And 5.10 and earlier did not have
> the code that disabled preemption, so they are fine in that regard.
> 
> This was tested by attaching a bpf program doing a non-0 arguments
> trace_printk at sys_enter and a 0 arguments snprintf at local_timer_entry.
> 
> Dave Marchevsky (1):
>   bpf: Merge printk and seq_printf VARARG max macros
> 
> Jiri Olsa (3):
>   bpf: Add struct for bin_args arg in bpf_bprintf_prepare
>   bpf: Do cleanup in bpf_bprintf_cleanup only when needed
>   bpf: Remove trace_printk_lock
> 
>  include/linux/bpf.h      | 14 ++++++--
>  kernel/bpf/helpers.c     | 71 ++++++++++++++++++++++------------------
>  kernel/bpf/verifier.c    |  3 +-
>  kernel/trace/bpf_trace.c | 39 ++++++++++------------
>  4 files changed, 72 insertions(+), 55 deletions(-)
> 
> -- 
> 2.34.1
> 
> 

All now queued up, thanks!

greg k-h