Re: [PATCH] tracing: remove __printf() attribute on __ftrace_vbprintk()

[Jeff Layton <jlayton@kernel.org>]

On Mon, 2026-02-02 at 10:58 +0100, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@arndb.de>
> 
> The sunrpc change to use trace_printk() for debugging caused
> a new warning for every instance of dprintk() in some configurations,
> when -Wformat-security is enabled:
> 
> fs/nfs/getroot.c: In function 'nfs_get_root':
> fs/nfs/getroot.c:90:17: error: format not a string literal and no format arguments [-Werror=format-security]
>    90 |                 nfs_errorf(fc, "NFS: Couldn't getattr on root");
> 
> I've been slowly chipping away at those warnings over time with the
> intention of enabling them by default in the future. While I could not
> figure out why this only happens for this one instance, I see that the
> __trace_bprintk() function is always called with a local variable as
> the format string, rather than a literal.
> 
> Remove the __printf(2,3) annotation on this function, as this is can
> only be validated for literals. The format strings still get checked
> because the underlying literal keeps getting passed into __trace_printk()
> in the "else" branch, which is not taken but still evaluated for
> compile-time warnings.
> 
> Fixes: ec7d8e68ef0e ("sunrpc: add a Kconfig option to redirect dfprintk() output to trace buffer")
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
>  include/linux/trace_printk.h | 1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/include/linux/trace_printk.h b/include/linux/trace_printk.h
> index bb5874097f24..2670ec7f4262 100644
> --- a/include/linux/trace_printk.h
> +++ b/include/linux/trace_printk.h
> @@ -107,7 +107,6 @@ do {									\
>  		__trace_printk(_THIS_IP_, fmt, ##args);			\
>  } while (0)
>  
> -extern __printf(2, 3)
>  int __trace_bprintk(unsigned long ip, const char *fmt, ...);
>  
>  extern __printf(2, 3)

Acked-by: Jeff Layton <jlayton@kernel.org>