[glibc] elf: Ignore LD_BIND_NOW and LD_BIND_NOT for setuid binaries

[glibc] elf: Ignore LD_BIND_NOW and LD_BIND_NOT for setuid binaries

[Adhemerval Zanella]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=61d848b554c8dd1f017b9d187b2a2f6675dbdbe4

commit 61d848b554c8dd1f017b9d187b2a2f6675dbdbe4
Author: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Date:   Wed Nov 22 17:43:24 2023 -0300

    elf: Ignore LD_BIND_NOW and LD_BIND_NOT for setuid binaries
    
    To avoid any environment variable to change setuid binaries
    semantics.
    
    Checked on x86_64-linux-gnu.
    Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>

Diff:
---
 elf/rtld.c                  | 8 ++++++--
 elf/tst-env-setuid.c        | 4 ++--
 sysdeps/generic/unsecvars.h | 2 ++
 3 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/elf/rtld.c b/elf/rtld.c
index 55cdb4836e..d9a6c33b31 100644
--- a/elf/rtld.c
+++ b/elf/rtld.c
@@ -2604,12 +2604,14 @@ process_envvars (struct dl_main_state *state)
 
 	case 8:
 	  /* Do we bind early?  */
-	  if (memcmp (envline, "BIND_NOW", 8) == 0)
+	  if (!__libc_enable_secure
+	      && memcmp (envline, "BIND_NOW", 8) == 0)
 	    {
 	      GLRO(dl_lazy) = envline[9] == '\0';
 	      break;
 	    }
-	  if (memcmp (envline, "BIND_NOT", 8) == 0)
+	  if (! __libc_enable_secure
+	      && memcmp (envline, "BIND_NOT", 8) == 0)
 	    GLRO(dl_bind_not) = envline[9] != '\0';
 	  break;
 
@@ -2686,6 +2688,8 @@ process_envvars (struct dl_main_state *state)
 
       if (GLRO(dl_debug_mask) != 0
 	  || GLRO(dl_verbose) != 0
+	  || GLRO(dl_lazy) != 1
+	  || GLRO(dl_bind_not) != 0
 	  || state->mode != rtld_mode_normal
 	  || state->version_info)
 	_exit (5);
diff --git a/elf/tst-env-setuid.c b/elf/tst-env-setuid.c
index b1d64ac085..9fa591a136 100644
--- a/elf/tst-env-setuid.c
+++ b/elf/tst-env-setuid.c
@@ -63,12 +63,12 @@ static const struct envvar_t filtered_envvars[] =
   { "LD_DEBUG_OUTPUT",         "/tmp/some-file" },
   { "LD_WARN",                 FILTERED_VALUE },
   { "LD_VERBOSE",              FILTERED_VALUE },
+  { "LD_BIND_NOW",             "0" },
+  { "LD_BIND_NOT",             "1" },
 };
 
 static const struct envvar_t unfiltered_envvars[] =
 {
-  { "LD_BIND_NOW",             "0" },
-  { "LD_BIND_NOT",             "1" },
   /* Non longer supported option.  */
   { "LD_ASSUME_KERNEL",        UNFILTERED_VALUE },
 };
diff --git a/sysdeps/generic/unsecvars.h b/sysdeps/generic/unsecvars.h
index 8975df4a14..f1724efe0f 100644
--- a/sysdeps/generic/unsecvars.h
+++ b/sysdeps/generic/unsecvars.h
@@ -7,6 +7,8 @@
   "GLIBC_TUNABLES\0"							      \
   "HOSTALIASES\0"							      \
   "LD_AUDIT\0"								      \
+  "LD_BIND_NOT\0"							      \
+  "LD_BIND_NOW\0"							      \
   "LD_DEBUG\0"								      \
   "LD_DEBUG_OUTPUT\0"							      \
   "LD_DYNAMIC_WEAK\0"							      \