[glibc] elf: Add GLIBC_TUNABLES to unsecvars

[Adhemerval Zanella <azanella@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=a72a4eb10b2d9aef7a53f9d2facf166a685d85fb

commit a72a4eb10b2d9aef7a53f9d2facf166a685d85fb
Author: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Date:   Mon Nov 6 17:25:35 2023 -0300

    elf: Add GLIBC_TUNABLES to unsecvars
    
    setuid/setgid process now ignores any glibc tunables, and filters out
    all environment variables that might changes its behavior. This patch
    also adds GLIBC_TUNABLES, so any spawned process by setuid/setgid
    processes should set tunable explicitly.
    
    Checked on x86_64-linux-gnu.
    
    Reviewed-by: Florian Weimer <fweimer@redhat.com>
    Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>

Diff:
---
 elf/tst-env-setuid-tunables.c | 32 ++++----------------------------
 sysdeps/generic/unsecvars.h   |  1 +
 2 files changed, 5 insertions(+), 28 deletions(-)

diff --git a/elf/tst-env-setuid-tunables.c b/elf/tst-env-setuid-tunables.c
index f0b92c97e7..2603007b7b 100644
--- a/elf/tst-env-setuid-tunables.c
+++ b/elf/tst-env-setuid-tunables.c
@@ -60,45 +60,21 @@ const char *teststrings[] =
   "glibc.not_valid.check=2",
 };
 
-const char *resultstrings[] =
-{
-  "glibc.malloc.mmap_threshold=4096",
-  "glibc.malloc.mmap_threshold=4096",
-  "glibc.malloc.mmap_threshold=4096",
-  "glibc.malloc.perturb=0x800",
-  "glibc.malloc.perturb=0x800:glibc.malloc.mmap_threshold=4096",
-  "glibc.malloc.perturb=0x800:glibc.malloc.mmap_threshold=4096",
-  "glibc.malloc.mmap_threshold=4096",
-  "glibc.malloc.mmap_threshold=4096",
-  "glibc.malloc.mmap_threshold=glibc.malloc.mmap_threshold=4096",
-  "",
-  "",
-  "",
-  "",
-  "",
-  "",
-  "",
-};
-
 static int
 test_child (int off)
 {
   const char *val = getenv ("GLIBC_TUNABLES");
+  int ret = 1;
 
   printf ("    [%d] GLIBC_TUNABLES is %s\n", off, val);
   fflush (stdout);
-  if (val != NULL && strcmp (val, resultstrings[off]) == 0)
-    return 0;
-
   if (val != NULL)
-    printf ("    [%d] Unexpected GLIBC_TUNABLES VALUE %s, expected %s\n",
-	    off, val, resultstrings[off]);
+    printf ("    [%d] Unexpected GLIBC_TUNABLES VALUE %s\n", off, val);
   else
-    printf ("    [%d] GLIBC_TUNABLES environment variable absent\n", off);
-
+    ret = 0;
   fflush (stdout);
 
-  return 1;
+  return ret;
 }
 
 static int
diff --git a/sysdeps/generic/unsecvars.h b/sysdeps/generic/unsecvars.h
index 8278c50a84..81397fb90b 100644
--- a/sysdeps/generic/unsecvars.h
+++ b/sysdeps/generic/unsecvars.h
@@ -4,6 +4,7 @@
 #define UNSECURE_ENVVARS \
   "GCONV_PATH\0"							      \
   "GETCONF_DIR\0"							      \
+  "GLIBC_TUNABLES\0"							      \
   "HOSTALIASES\0"							      \
   "LD_AUDIT\0"								      \
   "LD_DEBUG\0"								      \