Re: readlink: be quiet about overlong argument without '-f' option

[Theo de Raadt]

I feel the same way about this.  It can help in deep trees.

> On Mon, Sep 04, 2017 at 11:43:56AM -0500, Scott Cheloha wrote:
> > Thoughts?
> 
> The PATH_MAX check was introduced in rev 1.10 1997/09/23.  That was
> after the doumentation, so it might be a mistake that the man page
> was not updated.
> 
> The feature worked for 20 years, I see no reason to remove it.
> 
> Personally I prefer to see the error when something goes wrong.
> 
> bluhm
> 
> > Index: usr.bin/readlink/readlink.c
> > ===
> > RCS file: /cvs/src/usr.bin/readlink/readlink.c,v
> > retrieving revision 1.27
> > diff -u -p -r1.27 readlink.c
> > --- usr.bin/readlink/readlink.c 9 Oct 2015 01:37:08 -   1.27
> > +++ usr.bin/readlink/readlink.c 4 Sep 2017 15:57:47 -
> > @@ -64,14 +64,6 @@ main(int argc, char *argv[])
> > if (argc != 1)
> > usage();
> >  
> > -   n = strlen(argv[0]);
> > -   if (n > PATH_MAX - 1) {
> > -   fprintf(stderr,
> > -   "readlink: filename longer than PATH_MAX-1 (%d)\n",
> > -   PATH_MAX - 1);
> > -   exit(1);
> > -   }
> > -
> > if (fflag) {
> > if (realpath(argv[0], buf) == NULL)
> > err(1, "%s", argv[0]);
> 

Re: readlink: be quiet about overlong argument without '-f' option

[Alexander Bluhm]

On Mon, Sep 04, 2017 at 11:43:56AM -0500, Scott Cheloha wrote:
> Thoughts?

The PATH_MAX check was introduced in rev 1.10 1997/09/23.  That was
after the doumentation, so it might be a mistake that the man page
was not updated.

The feature worked for 20 years, I see no reason to remove it.

Personally I prefer to see the error when something goes wrong.

bluhm

> Index: usr.bin/readlink/readlink.c
> ===
> RCS file: /cvs/src/usr.bin/readlink/readlink.c,v
> retrieving revision 1.27
> diff -u -p -r1.27 readlink.c
> --- usr.bin/readlink/readlink.c   9 Oct 2015 01:37:08 -   1.27
> +++ usr.bin/readlink/readlink.c   4 Sep 2017 15:57:47 -
> @@ -64,14 +64,6 @@ main(int argc, char *argv[])
>   if (argc != 1)
>   usage();
>  
> - n = strlen(argv[0]);
> - if (n > PATH_MAX - 1) {
> - fprintf(stderr,
> - "readlink: filename longer than PATH_MAX-1 (%d)\n",
> - PATH_MAX - 1);
> - exit(1);
> - }
> -
>   if (fflag) {
>   if (realpath(argv[0], buf) == NULL)
>   err(1, "%s", argv[0]);

readlink: be quiet about overlong argument without '-f' option

[Scott Cheloha]

Hi,

readlink(1) has a check before calling readlink(2) that prints a
hand-rolled error message if your argument exceeds (PATH_MAX - 1)
bytes.

$ readlink $(perl -e 'print "z"x1024')

This contradicts the documentation, which says that absent the '-f'
flag nothing will be printed if the argument is not a symbolic link.
Exceeding (PATH_MAX - 1) bytes definitely excludes your argument, so
in that case readlink(1) should just say nothing.

With the '-f' option, readlink(1) already complains about an overlong
path or path component, so in that case the check is redundant.

$ readlink -f $(perl -e 'print "z"x256') 

Without the '-f' flag this change would put us in sync with GNU
readlink's behavior.  With the '-f' flag, it puts us in sync with GNU
realpath's behavior.

CC'd nicm@ because he expressed interest in this a few months back
when I submitted it as part of a larger patch that didn't make sense
in aggregate.

Thoughts?

--
Scott Cheloha

Index: usr.bin/readlink/readlink.c
===
RCS file: /cvs/src/usr.bin/readlink/readlink.c,v
retrieving revision 1.27
diff -u -p -r1.27 readlink.c
--- usr.bin/readlink/readlink.c 9 Oct 2015 01:37:08 -   1.27
+++ usr.bin/readlink/readlink.c 4 Sep 2017 15:57:47 -
@@ -64,14 +64,6 @@ main(int argc, char *argv[])
if (argc != 1)
usage();
 
-   n = strlen(argv[0]);
-   if (n > PATH_MAX - 1) {
-   fprintf(stderr,
-   "readlink: filename longer than PATH_MAX-1 (%d)\n",
-   PATH_MAX - 1);
-   exit(1);
-   }
-
if (fflag) {
if (realpath(argv[0], buf) == NULL)
err(1, "%s", argv[0]);