On Tue, 3 Feb 2026 17:45:29 +0100 Arnd Bergmann <[email protected]> wrote:
> From: Arnd Bergmann <[email protected]> > > 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. > > Move the __printf(2,3) annotation on this function from the declaration > to the caller. As this is can only be validated for literals, the ^ definition ? David > attribute on the declaration causes the warnings every time, but > removing it entirely introduces a new warning on the __ftrace_vbprintk() > definition. > > 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") > Acked-by: Jeff Layton <[email protected]> > Acked-by: Steven Rostedt (Google) <[email protected]> > Signed-off-by: Arnd Bergmann <[email protected]> > --- > v2: included fix for regression reported by kernel test robot <[email protected]> > --- > include/linux/trace_printk.h | 1 - > kernel/trace/trace_printk.c | 1 + > 2 files changed, 1 insertion(+), 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) > diff --git a/kernel/trace/trace_printk.c b/kernel/trace/trace_printk.c > index 29f6e95439b6..48c085fcae7a 100644 > --- a/kernel/trace/trace_printk.c > +++ b/kernel/trace/trace_printk.c > @@ -197,6 +197,7 @@ struct notifier_block module_trace_bprintk_format_nb = { > .notifier_call = module_trace_bprintk_format_notify, > }; > > +__printf(2, 3) > int __trace_bprintk(unsigned long ip, const char *fmt, ...) > { > int ret;
