Re: [PATCH v2] nfsd: Avoid strlen conflict in nfsd4_encode_components_esc()

[NeilBrown <neilb@ownmail.net>]

On Mon, 29 Sep 2025, Nathan Chancellor wrote:
> There is an error building nfs4xdr.c with CONFIG_SUNRPC_DEBUG_TRACE=y
> and CONFIG_FORTIFY_SOURCE=n due to the local variable strlen conflicting
> with the function strlen():
> 
>   In file included from include/linux/cpumask.h:11,
>                    from arch/x86/include/asm/paravirt.h:21,
>                    from arch/x86/include/asm/irqflags.h:102,
>                    from include/linux/irqflags.h:18,
>                    from include/linux/spinlock.h:59,
>                    from include/linux/mmzone.h:8,
>                    from include/linux/gfp.h:7,
>                    from include/linux/slab.h:16,
>                    from fs/nfsd/nfs4xdr.c:37:
>   fs/nfsd/nfs4xdr.c: In function 'nfsd4_encode_components_esc':
>   include/linux/kernel.h:321:46: error: called object 'strlen' is not a function or function pointer
>     321 |                 __trace_puts(_THIS_IP_, str, strlen(str));              \
>         |                                              ^~~~~~
>   include/linux/kernel.h:265:17: note: in expansion of macro 'trace_puts'
>     265 |                 trace_puts(fmt);                        \
>         |                 ^~~~~~~~~~
>   include/linux/sunrpc/debug.h:34:41: note: in expansion of macro 'trace_printk'
>      34 | #  define __sunrpc_printk(fmt, ...)     trace_printk(fmt, ##__VA_ARGS__)
>         |                                         ^~~~~~~~~~~~
>   include/linux/sunrpc/debug.h:42:17: note: in expansion of macro '__sunrpc_printk'
>      42 |                 __sunrpc_printk(fmt, ##__VA_ARGS__);                    \
>         |                 ^~~~~~~~~~~~~~~
>   include/linux/sunrpc/debug.h:25:9: note: in expansion of macro 'dfprintk'
>      25 |         dfprintk(FACILITY, fmt, ##__VA_ARGS__)
>         |         ^~~~~~~~
>   fs/nfsd/nfs4xdr.c:2646:9: note: in expansion of macro 'dprintk'
>    2646 |         dprintk("nfsd4_encode_components(%s)\n", components);
>         |         ^~~~~~~
>   fs/nfsd/nfs4xdr.c:2643:13: note: declared here
>    2643 |         int strlen, count=0;
>         |             ^~~~~~
> 
> This dprintk() instance is not particularly useful, so just remove it
> altogether.
> 
> At the same time, rename the strlen local variable to avoid any
> potential conflicts with strlen().
> 
> Fixes: ec7d8e68ef0e ("sunrpc: add a Kconfig option to redirect dfprintk() output to trace buffer")
> Signed-off-by: Nathan Chancellor <nathan@kernel.org>
> ---
> Changes in v2:
> - Remove dprintk() to remove usage of strlen()
> - Rename local strlen variable to avoid potential conflict in the future
> - Link to v1: https://patch.msgid.link/20250925-nfsd-fix-trace-printk-strlen-error-v1-1-1360530e4c6b@kernel.org
> ---
>  fs/nfsd/nfs4xdr.c | 10 ++++------
>  1 file changed, 4 insertions(+), 6 deletions(-)
> 
> diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
> index ea91bad4eee2..9fe8a413f688 100644
> --- a/fs/nfsd/nfs4xdr.c
> +++ b/fs/nfsd/nfs4xdr.c
> @@ -2640,11 +2640,9 @@ static __be32 nfsd4_encode_components_esc(struct xdr_stream *xdr, char sep,
>  	__be32 *p;
>  	__be32 pathlen;
>  	int pathlen_offset;
> -	int strlen, count=0;
> +	int str_len, count=0;
>  	char *str, *end, *next;
>  
> -	dprintk("nfsd4_encode_components(%s)\n", components);
> -
>  	pathlen_offset = xdr->buf->len;
>  	p = xdr_reserve_space(xdr, 4);
>  	if (!p)
> @@ -2670,9 +2668,9 @@ static __be32 nfsd4_encode_components_esc(struct xdr_stream *xdr, char sep,
>  			for (; *end && (*end != sep); end++)
>  				/* find sep or end of string */;
>  
> -		strlen = end - str;
> -		if (strlen) {
> -			if (xdr_stream_encode_opaque(xdr, str, strlen) < 0)
> +		str_len = end - str;
> +		if (str_len) {
> +			if (xdr_stream_encode_opaque(xdr, str, str_len) < 0)
>  				return nfserr_resource;

I probably should have said something earlier, and this is definitely
bike-shedding material, but .... "str_len" is not a whole lot nicer than
"strlen" (or "i") ...


   if (end > str) {
	if (xdr_stream_encode_opaque(xdr, str, end - str) < 0)

??

NeilBrown