glibc/SOURCES/glibc-rh1817513-47.patch
2021-09-16 08:48:07 +00:00

374 lines
12 KiB
Diff
Raw Blame History

This file contains invisible Unicode characters

This file contains invisible Unicode characters that are indistinguishable to humans but may be processed differently by a computer. If you think that this is intentional, you can safely ignore this warning. Use the Escape button to reveal them.

commit 4c6e0415ef206a595c62d5d37e3b9a821782c533
Author: Florian Weimer <fweimer@redhat.com>
Date: Fri Apr 3 13:17:48 2020 +0200
elf: Simplify handling of lists of audit strings
All list elements are colon-separated strings, and there is a hard
upper limit for the number of audit modules, so it is possible to
pre-allocate a fixed-size array of strings to which the LD_AUDIT
environment variable and --audit arguments are added.
Also eliminate the global variables for the audit list because
the list is only needed briefly during startup.
There is a slight behavior change: All duplicate LD_AUDIT environment
variables are now processed, not just the last one as before. However,
such environment vectors are invalid anyway.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
diff --git a/elf/rtld.c b/elf/rtld.c
index f755dc30331f799f..c39cb8f2cd4bb1cc 100644
--- a/elf/rtld.c
+++ b/elf/rtld.c
@@ -43,6 +43,7 @@
#include <stap-probe.h>
#include <stackinfo.h>
#include <not-cancel.h>
+#include <array_length.h>
#include <assert.h>
@@ -107,8 +108,53 @@ static void print_missing_version (int errcode, const char *objname,
/* Print the various times we collected. */
static void print_statistics (const hp_timing_t *total_timep);
-/* Add audit objects. */
-static void process_dl_audit (char *str);
+/* Length limits for names and paths, to protect the dynamic linker,
+ particularly when __libc_enable_secure is active. */
+#ifdef NAME_MAX
+# define SECURE_NAME_LIMIT NAME_MAX
+#else
+# define SECURE_NAME_LIMIT 255
+#endif
+#ifdef PATH_MAX
+# define SECURE_PATH_LIMIT PATH_MAX
+#else
+# define SECURE_PATH_LIMIT 1024
+#endif
+
+/* Strings containing colon-separated lists of audit modules. */
+struct audit_list
+{
+ /* Array of strings containing colon-separated path lists. Each
+ audit module needs its own namespace, so pre-allocate the largest
+ possible list. */
+ const char *audit_strings[DL_NNS];
+
+ /* Number of entries added to audit_strings. */
+ size_t length;
+
+ /* Index into the audit_strings array (for the iteration phase). */
+ size_t current_index;
+
+ /* Tail of audit_strings[current_index] which still needs
+ processing. */
+ const char *current_tail;
+
+ /* Scratch buffer for returning a name which is part of the strings
+ in audit_strings. */
+ char fname[SECURE_NAME_LIMIT];
+};
+
+/* Creates an empty audit list. */
+static void audit_list_init (struct audit_list *);
+
+/* Add a string to the end of the audit list, for later parsing. Must
+ not be called after audit_list_next. */
+static void audit_list_add_string (struct audit_list *, const char *);
+
+/* Extract the next audit module from the audit list. Only modules
+ for which dso_name_valid_for_suid is true are returned. Must be
+ called after all the audit_list_add_string calls. */
+static const char *audit_list_next (struct audit_list *);
/* This is a list of all the modes the dynamic loader can be in. */
enum mode { normal, list, verify, trace };
@@ -116,7 +162,7 @@ enum mode { normal, list, verify, trace };
/* Process all environments variables the dynamic linker must recognize.
Since all of them start with `LD_' we are a bit smarter while finding
all the entries. */
-static void process_envvars (enum mode *modep);
+static void process_envvars (enum mode *modep, struct audit_list *);
#ifdef DL_ARGV_NOT_RELRO
int _dl_argc attribute_hidden;
@@ -144,19 +190,6 @@ uintptr_t __pointer_chk_guard_local
strong_alias (__pointer_chk_guard_local, __pointer_chk_guard)
#endif
-/* Length limits for names and paths, to protect the dynamic linker,
- particularly when __libc_enable_secure is active. */
-#ifdef NAME_MAX
-# define SECURE_NAME_LIMIT NAME_MAX
-#else
-# define SECURE_NAME_LIMIT 255
-#endif
-#ifdef PATH_MAX
-# define SECURE_PATH_LIMIT PATH_MAX
-#else
-# define SECURE_PATH_LIMIT 1024
-#endif
-
/* Check that AT_SECURE=0, or that the passed name does not contain
directories and is not overly long. Reject empty names
unconditionally. */
@@ -174,89 +207,75 @@ dso_name_valid_for_suid (const char *p)
return *p != '\0';
}
-/* LD_AUDIT variable contents. Must be processed before the
- audit_list below. */
-const char *audit_list_string;
-
-/* Cyclic list of auditing DSOs. audit_list->next is the first
- element. */
-static struct audit_list
+static void
+audit_list_init (struct audit_list *list)
{
- const char *name;
- struct audit_list *next;
-} *audit_list;
+ list->length = 0;
+ list->current_index = 0;
+ list->current_tail = NULL;
+}
-/* Iterator for audit_list_string followed by audit_list. */
-struct audit_list_iter
+static void
+audit_list_add_string (struct audit_list *list, const char *string)
{
- /* Tail of audit_list_string still needing processing, or NULL. */
- const char *audit_list_tail;
+ /* Empty strings do not load anything. */
+ if (*string == '\0')
+ return;
- /* The list element returned in the previous iteration. NULL before
- the first element. */
- struct audit_list *previous;
+ if (list->length == array_length (list->audit_strings))
+ _dl_fatal_printf ("Fatal glibc error: Too many audit modules requested\n");
- /* Scratch buffer for returning a name which is part of
- audit_list_string. */
- char fname[SECURE_NAME_LIMIT];
-};
+ list->audit_strings[list->length++] = string;
-/* Initialize an audit list iterator. */
-static void
-audit_list_iter_init (struct audit_list_iter *iter)
-{
- iter->audit_list_tail = audit_list_string;
- iter->previous = NULL;
+ /* Initialize processing of the first string for
+ audit_list_next. */
+ if (list->length == 1)
+ list->current_tail = string;
}
-/* Iterate through both audit_list_string and audit_list. */
static const char *
-audit_list_iter_next (struct audit_list_iter *iter)
+audit_list_next (struct audit_list *list)
{
- if (iter->audit_list_tail != NULL)
+ if (list->current_tail == NULL)
+ return NULL;
+
+ while (true)
{
- /* First iterate over audit_list_string. */
- while (*iter->audit_list_tail != '\0')
+ /* Advance to the next string in audit_strings if the current
+ string has been exhausted. */
+ while (*list->current_tail == '\0')
{
- /* Split audit list at colon. */
- size_t len = strcspn (iter->audit_list_tail, ":");
- if (len > 0 && len < sizeof (iter->fname))
+ ++list->current_index;
+ if (list->current_index == list->length)
{
- memcpy (iter->fname, iter->audit_list_tail, len);
- iter->fname[len] = '\0';
+ list->current_tail = NULL;
+ return NULL;
}
- else
- /* Do not return this name to the caller. */
- iter->fname[0] = '\0';
-
- /* Skip over the substring and the following delimiter. */
- iter->audit_list_tail += len;
- if (*iter->audit_list_tail == ':')
- ++iter->audit_list_tail;
-
- /* If the name is valid, return it. */
- if (dso_name_valid_for_suid (iter->fname))
- return iter->fname;
- /* Otherwise, wrap around and try the next name. */
+ list->current_tail = list->audit_strings[list->current_index];
}
- /* Fall through to the procesing of audit_list. */
- }
- if (iter->previous == NULL)
- {
- if (audit_list == NULL)
- /* No pre-parsed audit list. */
- return NULL;
- /* Start of audit list. The first list element is at
- audit_list->next (cyclic list). */
- iter->previous = audit_list->next;
- return iter->previous->name;
+ /* Split the in-string audit list at the next colon colon. */
+ size_t len = strcspn (list->current_tail, ":");
+ if (len > 0 && len < sizeof (list->fname))
+ {
+ memcpy (list->fname, list->current_tail, len);
+ list->fname[len] = '\0';
+ }
+ else
+ /* Mark the name as unusable for dso_name_valid_for_suid. */
+ list->fname[0] = '\0';
+
+ /* Skip over the substring and the following delimiter. */
+ list->current_tail += len;
+ if (*list->current_tail == ':')
+ ++list->current_tail;
+
+ /* If the name is valid, return it. */
+ if (dso_name_valid_for_suid (list->fname))
+ return list->fname;
+
+ /* Otherwise wrap around to find the next list element. . */
}
- if (iter->previous == audit_list)
- /* Cyclic list wrap-around. */
- return NULL;
- iter->previous = iter->previous->next;
- return iter->previous->name;
}
/* Set nonzero during loading and initialization of executable and
@@ -1060,15 +1079,13 @@ notify_audit_modules_of_loaded_object (struct link_map *map)
/* Load all audit modules. */
static void
-load_audit_modules (struct link_map *main_map)
+load_audit_modules (struct link_map *main_map, struct audit_list *audit_list)
{
struct audit_ifaces *last_audit = NULL;
- struct audit_list_iter al_iter;
- audit_list_iter_init (&al_iter);
while (true)
{
- const char *name = audit_list_iter_next (&al_iter);
+ const char *name = audit_list_next (audit_list);
if (name == NULL)
break;
load_audit_module (name, &last_audit);
@@ -1100,6 +1117,9 @@ dl_main (const ElfW(Phdr) *phdr,
bool rtld_is_main = false;
void *tcbp = NULL;
+ struct audit_list audit_list;
+ audit_list_init (&audit_list);
+
GL(dl_init_static_tls) = &_dl_nothread_init_static_tls;
#if defined SHARED && defined _LIBC_REENTRANT \
@@ -1113,7 +1133,7 @@ dl_main (const ElfW(Phdr) *phdr,
GL(dl_make_stack_executable_hook) = &_dl_make_stack_executable;
/* Process the environment variable which control the behaviour. */
- process_envvars (&mode);
+ process_envvars (&mode, &audit_list);
/* Set up a flag which tells we are just starting. */
_dl_starting_up = 1;
@@ -1185,7 +1205,7 @@ dl_main (const ElfW(Phdr) *phdr,
}
else if (! strcmp (_dl_argv[1], "--audit") && _dl_argc > 2)
{
- process_dl_audit (_dl_argv[2]);
+ audit_list_add_string (&audit_list, _dl_argv[2]);
_dl_skip_args += 2;
_dl_argc -= 2;
@@ -1612,8 +1632,7 @@ ERROR: '%s': cannot process note segment.\n", _dl_argv[0]);
/* If we have auditing DSOs to load, do it now. */
bool need_security_init = true;
- if (__glibc_unlikely (audit_list != NULL)
- || __glibc_unlikely (audit_list_string != NULL))
+ if (audit_list.length > 0)
{
/* Since we start using the auditing DSOs right away we need to
initialize the data structures now. */
@@ -1626,7 +1645,7 @@ ERROR: '%s': cannot process note segment.\n", _dl_argv[0]);
security_init ();
need_security_init = false;
- load_audit_modules (main_map);
+ load_audit_modules (main_map, &audit_list);
}
/* Keep track of the currently loaded modules to count how many
@@ -2500,30 +2519,6 @@ a filename can be specified using the LD_DEBUG_OUTPUT environment variable.\n");
}
}
-static void
-process_dl_audit (char *str)
-{
- /* The parameter is a colon separated list of DSO names. */
- char *p;
-
- while ((p = (strsep) (&str, ":")) != NULL)
- if (dso_name_valid_for_suid (p))
- {
- /* This is using the local malloc, not the system malloc. The
- memory can never be freed. */
- struct audit_list *newp = malloc (sizeof (*newp));
- newp->name = p;
-
- if (audit_list == NULL)
- audit_list = newp->next = newp;
- else
- {
- newp->next = audit_list->next;
- audit_list = audit_list->next = newp;
- }
- }
-}
-
/* Process all environments variables the dynamic linker must recognize.
Since all of them start with `LD_' we are a bit smarter while finding
all the entries. */
@@ -2531,7 +2526,7 @@ extern char **_environ attribute_hidden;
static void
-process_envvars (enum mode *modep)
+process_envvars (enum mode *modep, struct audit_list *audit_list)
{
char **runp = _environ;
char *envline;
@@ -2571,7 +2566,7 @@ process_envvars (enum mode *modep)
break;
}
if (memcmp (envline, "AUDIT", 5) == 0)
- audit_list_string = &envline[6];
+ audit_list_add_string (audit_list, &envline[6]);
break;
case 7: