[PATCH] policycoreutils/secon: fix discarded-qualifiers warning with glibc 2.43

[PATCH] policycoreutils/secon: fix discarded-qualifiers warning with glibc 2.43

[Dustin Kirkland]

https://github.com/SELinuxProject/selinux/pull/507

In my_getXcon_raw(), ptr is declared as const char * but is
assigned from fgets(), which returns char *. With glibc 2.43,
strchr(const char *, int) now correctly returns const char *
(matching the constness of its input), so the subsequent assignment
to char *tmp triggers a build failure:

secon.c: In function 'my_getXcon_raw':
secon.c:365:18: error: initialization discards 'const' qualifier from
pointer target type [-Werror=discarded-qualifiers]
  365 |         char *tmp = strchr(ptr, '\n');
      |                     ^~~~~~
This breaks builds on any system with glibc 2.43+ and gcc with
-Werror (which the SELinux Makefile uses).

Fix
The const on ptr was always incorrect:

fgets() returns char * (a mutable pointer into buf, which is
char[4096])
The result of strchr() through ptr is immediately used mutably:
*tmp = 0
Remove the erroneous const qualifier from ptr.

Relation to issue #506
This is the same class of bug reported in #506
(libselinux/src/selinux_config.c:284). That issue covers
strrchr() in selinux_set_policy_root(); this patch covers
strchr() in my_getXcon_raw() in policycoreutils/secon/secon.c.

Both instances have the same root cause: a local variable was
unnecessarily const-qualified, which glibc 2.43's strengthened
strchr/strrchr const-propagation now correctly rejects.

Testing
Verified by building policycoreutils version 3.10 against glibc 2.43
on a Wolfi-based system (Chainguard) where this was a build failure.

Signed-off-by: Dustin Kirkland dustin.kirkland@chainguard.dev

From fe074290a6eff8f12345350ea2938bb0e5e5bc5a Mon Sep 17 00:00:00 2001
From: Dustin Kirkland <dustin.kirkland@chainguard.dev>
Date: Thu, 12 Mar 2026 09:55:17 -0500
Subject: [PATCH] policycoreutils/secon: fix discarded-qualifiers warning with
 glibc 2.43

In my_getXcon_raw(), ptr is declared as const char * but is assigned
from fgets(), which returns char *. With glibc 2.43, strchr(const char
*, int) now returns const char *, so the subsequent assignment to
char *tmp triggers:

  secon.c:365:18: error: initialization discards 'const' qualifier
  from pointer target type [-Werror=discarded-qualifiers]

The const on ptr was always incorrect: fgets() returns a mutable
pointer into buf (a char[4096]), and the result of strchr() through
ptr is written to via *tmp = 0. Remove the erroneous const.

This is the same class of bug reported in issue #506
(libselinux/src/selinux_config.c:284). The fix here is analogous:
the variable should not have been const-qualified in the first place.

Signed-off-by: Dustin Kirkland <dustin.kirkland@chainguard.dev>
---
 policycoreutils/secon/secon.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/policycoreutils/secon/secon.c b/policycoreutils/secon/secon.c
index d624fa136f..9a05cf1959 100644
--- a/policycoreutils/secon/secon.c
+++ b/policycoreutils/secon/secon.c
@@ -348,7 +348,7 @@ static int my_getXcon_raw(pid_t pid, char  **con,
const char *val)
 {
  char buf[4096];
  FILE *fp = NULL;
- const char *ptr = NULL;
+ char *ptr = NULL;

  snprintf(buf, sizeof(buf), "%s/%ld/attr/%s", "/proc", (long int)pid,
  val);

[PATCH] policycoreutils/secon: fix discarded-qualifiers warning with glibc 2.43

[Petr Lautrbach]

From: Dustin Kirkland <dustin.kirkland@chainguard.dev>

In my_getXcon_raw(), ptr is declared as const char * but is assigned
from fgets(), which returns char *. With glibc 2.43, strchr(const char
*, int) now returns const char *, so the subsequent assignment to
char *tmp triggers:

  secon.c:365:18: error: initialization discards 'const' qualifier
  from pointer target type [-Werror=discarded-qualifiers]

The const on ptr was always incorrect: fgets() returns a mutable
pointer into buf (a char[4096]), and the result of strchr() through
ptr is written to via *tmp = 0. Remove the erroneous const.

This is the same class of bug reported in issue #506
(libselinux/src/selinux_config.c:284). The fix here is analogous:
the variable should not have been const-qualified in the first place.

Signed-off-by: Dustin Kirkland <dustin.kirkland@chainguard.dev>
---

Resent of the original patch downloaded from githu as the original patch in the
email was slightly broken.

 policycoreutils/secon/secon.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/policycoreutils/secon/secon.c b/policycoreutils/secon/secon.c
index d624fa136f3e..9a05cf1959ba 100644
--- a/policycoreutils/secon/secon.c
+++ b/policycoreutils/secon/secon.c
@@ -348,7 +348,7 @@ static int my_getXcon_raw(pid_t pid, char  **con, const char *val)
 {
 	char buf[4096];
 	FILE *fp = NULL;
-	const char *ptr = NULL;
+	char *ptr = NULL;
 
 	snprintf(buf, sizeof(buf), "%s/%ld/attr/%s", "/proc", (long int)pid,
 		 val);
-- 
2.54.0

Re: [PATCH] policycoreutils/secon: fix discarded-qualifiers warning with glibc 2.43

[Petr Lautrbach]

Petr Lautrbach <lautrbach@redhat.com> writes:

> From: Dustin Kirkland <dustin.kirkland@chainguard.dev>
>
> In my_getXcon_raw(), ptr is declared as const char * but is assigned
> from fgets(), which returns char *. With glibc 2.43, strchr(const char
> *, int) now returns const char *, so the subsequent assignment to
> char *tmp triggers:
>
>   secon.c:365:18: error: initialization discards 'const' qualifier
>   from pointer target type [-Werror=discarded-qualifiers]
>
> The const on ptr was always incorrect: fgets() returns a mutable
> pointer into buf (a char[4096]), and the result of strchr() through
> ptr is written to via *tmp = 0. Remove the erroneous const.
>
> This is the same class of bug reported in issue #506
> (libselinux/src/selinux_config.c:284). The fix here is analogous:
> the variable should not have been const-qualified in the first place.
>
> Signed-off-by: Dustin Kirkland <dustin.kirkland@chainguard.dev>

Acked-by: Petr Lautrbach <lautrbach@redhat.com>


> ---
>
> Resent of the original patch downloaded from githu as the original patch in the
> email was slightly broken.
>
>  policycoreutils/secon/secon.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/policycoreutils/secon/secon.c b/policycoreutils/secon/secon.c
> index d624fa136f3e..9a05cf1959ba 100644
> --- a/policycoreutils/secon/secon.c
> +++ b/policycoreutils/secon/secon.c
> @@ -348,7 +348,7 @@ static int my_getXcon_raw(pid_t pid, char  **con, const char *val)
>  {
>  	char buf[4096];
>  	FILE *fp = NULL;
> -	const char *ptr = NULL;
> +	char *ptr = NULL;
>  
>  	snprintf(buf, sizeof(buf), "%s/%ld/attr/%s", "/proc", (long int)pid,
>  		 val);
> -- 
> 2.54.0

Re: [PATCH] policycoreutils/secon: fix discarded-qualifiers warning with glibc 2.43

[James Carter]

On Mon, Apr 27, 2026 at 8:54 AM Petr Lautrbach <lautrbach@redhat.com> wrote:
>
> Petr Lautrbach <lautrbach@redhat.com> writes:
>
> > From: Dustin Kirkland <dustin.kirkland@chainguard.dev>
> >
> > In my_getXcon_raw(), ptr is declared as const char * but is assigned
> > from fgets(), which returns char *. With glibc 2.43, strchr(const char
> > *, int) now returns const char *, so the subsequent assignment to
> > char *tmp triggers:
> >
> >   secon.c:365:18: error: initialization discards 'const' qualifier
> >   from pointer target type [-Werror=discarded-qualifiers]
> >
> > The const on ptr was always incorrect: fgets() returns a mutable
> > pointer into buf (a char[4096]), and the result of strchr() through
> > ptr is written to via *tmp = 0. Remove the erroneous const.
> >
> > This is the same class of bug reported in issue #506
> > (libselinux/src/selinux_config.c:284). The fix here is analogous:
> > the variable should not have been const-qualified in the first place.
> >
> > Signed-off-by: Dustin Kirkland <dustin.kirkland@chainguard.dev>
>
> Acked-by: Petr Lautrbach <lautrbach@redhat.com>
>

Merged.
Thanks,
Jim

>
> > ---
> >
> > Resent of the original patch downloaded from githu as the original patch in the
> > email was slightly broken.
> >
> >  policycoreutils/secon/secon.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/policycoreutils/secon/secon.c b/policycoreutils/secon/secon.c
> > index d624fa136f3e..9a05cf1959ba 100644
> > --- a/policycoreutils/secon/secon.c
> > +++ b/policycoreutils/secon/secon.c
> > @@ -348,7 +348,7 @@ static int my_getXcon_raw(pid_t pid, char  **con, const char *val)
> >  {
> >       char buf[4096];
> >       FILE *fp = NULL;
> > -     const char *ptr = NULL;
> > +     char *ptr = NULL;
> >
> >       snprintf(buf, sizeof(buf), "%s/%ld/attr/%s", "/proc", (long int)pid,
> >                val);
> > --
> > 2.54.0
>
>