[PATCH v2] elf/rtld: Count skipped environment variables for enable_secure
Joe Simmons-Talbott
josimmon@redhat.com
Thu Mar 7 21:40:29 GMT 2024
When using the glibc.rtld.enable_secure tunable we need to keep track of
the count of environment variables we skip due to __libc_enable_secure
being set and adjust the auxv section of the stack. This fixes an
assertion when running ld.so directly with glibc.rtld.enable_secure set.
elf/rtld.c:1324 assert (auxv == sp + 1);
---
Changes to v1:
* Add comment explaining how and why skip_env is adjusted.
elf/rtld.c | 31 +++++++++++++++++++++++--------
1 file changed, 23 insertions(+), 8 deletions(-)
diff --git a/elf/rtld.c b/elf/rtld.c
index ac4bb23652..e9525ea987 100644
--- a/elf/rtld.c
+++ b/elf/rtld.c
@@ -155,7 +155,7 @@ static void dl_main_state_init (struct dl_main_state *state);
Since all of them start with `LD_' we are a bit smarter while finding
all the entries. */
extern char **_environ attribute_hidden;
-static void process_envvars (struct dl_main_state *state);
+static int process_envvars (struct dl_main_state *state);
int _dl_argc attribute_relro attribute_hidden;
char **_dl_argv attribute_relro = NULL;
@@ -1287,7 +1287,7 @@ rtld_setup_main_map (struct link_map *main_map)
_dl_argv and _dl_argc accordingly. Those arguments are removed from
argv here. */
static void
-_dl_start_args_adjust (int skip_args)
+_dl_start_args_adjust (int skip_args, int skip_env)
{
void **sp = (void **) (_dl_argv - skip_args - 1);
void **p = sp + skip_args;
@@ -1319,7 +1319,7 @@ _dl_start_args_adjust (int skip_args)
while (*p != NULL);
#ifdef HAVE_AUX_VECTOR
- void **auxv = (void **) GLRO(dl_auxv) - skip_args;
+ void **auxv = (void **) GLRO(dl_auxv) - skip_args - skip_env;
GLRO(dl_auxv) = (ElfW(auxv_t) *) auxv; /* Aliasing violation. */
assert (auxv == sp + 1);
@@ -1350,6 +1350,7 @@ dl_main (const ElfW(Phdr) *phdr,
unsigned int i;
bool rtld_is_main = false;
void *tcbp = NULL;
+ int skip_env = 0;
struct dl_main_state state;
dl_main_state_init (&state);
@@ -1363,7 +1364,7 @@ dl_main (const ElfW(Phdr) *phdr,
#endif
/* Process the environment variable which control the behaviour. */
- process_envvars (&state);
+ skip_env = process_envvars (&state);
#ifndef HAVE_INLINED_SYSCALLS
/* Set up a flag which tells we are just starting. */
@@ -1628,7 +1629,7 @@ dl_main (const ElfW(Phdr) *phdr,
_dl_argv[0] = argv0;
/* Adjust arguments for the application entry point. */
- _dl_start_args_adjust (_dl_argv - orig_argv);
+ _dl_start_args_adjust (_dl_argv - orig_argv, skip_env);
}
else
{
@@ -2532,11 +2533,12 @@ a filename can be specified using the LD_DEBUG_OUTPUT environment variable.\n");
}
}
-static void
+static int
process_envvars_secure (struct dl_main_state *state)
{
char **runp = _environ;
char *envline;
+ int skip_env = 0;
while ((envline = _dl_next_ld_env_entry (&runp)) != NULL)
{
@@ -2578,6 +2580,14 @@ process_envvars_secure (struct dl_main_state *state)
const char *nextp = UNSECURE_ENVVARS;
do
{
+ /* Keep track of the number of environment variables that were set in
+ the environment and are unset below. Use getenv() which returns
+ non-NULL if the variable is set in the environment. This count is
+ needed if we need to adjust the location of the AUX vector on the
+ stack when running ld.so directly. */
+ if (getenv (nextp) != NULL)
+ skip_env++;
+
unsetenv (nextp);
nextp = strchr (nextp, '\0') + 1;
}
@@ -2590,6 +2600,8 @@ process_envvars_secure (struct dl_main_state *state)
|| state->mode != rtld_mode_normal
|| state->version_info)
_exit (5);
+
+ return skip_env;
}
static void
@@ -2743,13 +2755,16 @@ process_envvars_default (struct dl_main_state *state)
}
}
-static void
+static int
process_envvars (struct dl_main_state *state)
{
+ int skip_env = 0;
if (__glibc_unlikely (__libc_enable_secure))
- process_envvars_secure (state);
+ skip_env += process_envvars_secure (state);
else
process_envvars_default (state);
+
+ return skip_env;
}
#if HP_TIMING_INLINE
--
2.43.2
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