elf: Ignore LD_PROFILE for setuid binaries

Loader does not ignore LD_PROFILE in secure-execution mode (different
than man-page states [1]), rather it uses a different path
(/var/profile) and ignore LD_PROFILE_OUTPUT.

Allowing secure-execution profiling is already a non good security
boundary, since it enables different code paths and extra OS access by
the process.  But by ignoring LD_PROFILE_OUTPUT, the resulting profile
file might also be acceded in a racy manner since the file name does not
use any process-specific information (such as pid, timing, etc.).

Another side-effect is it forces lazy binding even on libraries that
might be with DF_BIND_NOW.

[1] https://man7.org/linux/man-pages/man8/ld.so.8.html
Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>

diff --git a/elf/Makefile b/elf/Makefile
index 1af8ca4..414fdbd 100644 (file)
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -3002,3 +3002,6 @@ $(objpfx)tst-non-directory-path.out: tst-non-directory-path.sh \
        $(evaluate-test)
 
 tst-env-setuid-ARGS = -- $(host-test-program-cmd)
+
+# Reuse a module with a SONAME, to specific as the LD_PROFILE.
+$(objpfx)tst-env-setuid: $(objpfx)tst-sonamemove-runmod2.so

diff --git a/elf/rtld.c b/elf/rtld.c
index 51b6d9f..a09cf2a 100644 (file)
--- a/elf/rtld.c
+++ b/elf/rtld.c
@@ -361,6 +361,7 @@ struct rtld_global_ro _rtld_global_ro attribute_relro =
     ._dl_fpu_control = _FPU_DEFAULT,
     ._dl_pagesize = EXEC_PAGESIZE,
     ._dl_inhibit_cache = 0,
+    ._dl_profile_output = "/var/tmp",
 
     /* Function pointers.  */
     ._dl_debug_printf = _dl_debug_printf,
@@ -2534,10 +2535,6 @@ process_envvars (struct dl_main_state *state)
   char *envline;
   char *debug_output = NULL;
 
-  /* This is the default place for profiling data file.  */
-  GLRO(dl_profile_output)
-    = &"/var/tmp\0/var/profile"[__libc_enable_secure ? 9 : 0];
-
   while ((envline = _dl_next_ld_env_entry (&runp)) != NULL)
     {
       size_t len = 0;
@@ -2586,7 +2583,8 @@ process_envvars (struct dl_main_state *state)
            }
 
          /* Which shared object shall be profiled.  */
-         if (memcmp (envline, "PROFILE", 7) == 0 && envline[8] != '\0')
+         if (!__libc_enable_secure
+             && memcmp (envline, "PROFILE", 7) == 0 && envline[8] != '\0')
            GLRO(dl_profile) = &envline[8];
          break;
 

diff --git a/elf/tst-env-setuid.c b/elf/tst-env-setuid.c
index ba295a6..76b8e1f 100644 (file)
--- a/elf/tst-env-setuid.c
+++ b/elf/tst-env-setuid.c
@@ -34,6 +34,9 @@ static char SETGID_CHILD[] = "setgid-child";
 
 #define FILTERED_VALUE   "some-filtered-value"
 #define UNFILTERED_VALUE "some-unfiltered-value"
+/* It assumes no other programs is being profile with a library with same
+   SONAME using the default folder.  */
+#define PROFILE_LIB      "tst-sonamemove-runmod2.so"
 
 struct envvar_t
 {
@@ -50,7 +53,7 @@ static const struct envvar_t filtered_envvars[] =
   { "LD_HWCAP_MASK",           FILTERED_VALUE },
   { "LD_LIBRARY_PATH",         FILTERED_VALUE },
   { "LD_PRELOAD",              FILTERED_VALUE },
-  { "LD_PROFILE",              FILTERED_VALUE },
+  { "LD_PROFILE",              "tst-sonamemove-runmod2.so" },
   { "MALLOC_ARENA_MAX",        FILTERED_VALUE },
   { "MALLOC_PERTURB_",         FILTERED_VALUE },
   { "MALLOC_TRACE",            FILTERED_VALUE },
@@ -87,6 +90,13 @@ test_child (void)
       ret |= !(env != NULL && strcmp (env, e->value) == 0);
     }
 
+  /* Also check if no profile file was created.  */
+  {
+    char *profilepath = xasprintf ("/var/tmp/%s.profile", PROFILE_LIB);
+    ret |= !access (profilepath, R_OK);
+    free (profilepath);
+  }
+
   return ret;
 }