lib/libc/net/nsdispatch.c: Fix missing unlock and add locking annotations
The error cases (goto fin) of _nsdispatch were missing the unlock. This change also drops the checks for __isthreaded since the pthread stubs are already no-ops if threads are not being used. Dropping those conditionals allows clang's thread safety analysis to deal with the file and also makes the code a bit more readable. While touching the file also add a few more assertions in debug mode that the right locks are held. Reviewed By: markj Differential Revision: https://reviews.freebsd.org/D29372
This commit is contained in:
Alex Richardson
parent
142cb88bc6
commit
5245bf7b92
@ -69,6 +69,7 @@ __FBSDID("$FreeBSD$");
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#include <sys/param.h>
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#include <sys/stat.h>
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#include <assert.h>
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#include <dlfcn.h>
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#include <errno.h>
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#include <fcntl.h>
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@ -76,6 +77,7 @@ __FBSDID("$FreeBSD$");
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#include <nsswitch.h>
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#include <pthread.h>
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#include <pthread_np.h>
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#include <stdatomic.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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@ -97,7 +99,52 @@ enum _nss_constants {
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* Global NSS data structures are mostly read-only, but we update
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* them when we read or re-read the nsswitch.conf.
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*/
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static pthread_rwlock_t nss_lock = PTHREAD_RWLOCK_INITIALIZER;
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static pthread_rwlock_t nss_lock = PTHREAD_RWLOCK_INITIALIZER;
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#ifndef NDEBUG
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static void *nss_wlock_owner __guarded_by(nss_lock);
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#endif
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static inline /* __lock_annotate(locks_excluded(nss_lock)) */
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__locks_exclusive(nss_lock) int
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nss_wlock(void)
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{
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int err;
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err = _pthread_rwlock_wrlock(&nss_lock);
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#ifndef NDEBUG
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assert(nss_wlock_owner == NULL);
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nss_wlock_owner = _pthread_self();
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#endif
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assert(err == 0 && "Locking should not have failed!");
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return (err);
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}
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/*
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* XXX: The manpage says already held lock may result in EDEADLK, but
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* actually libthr returns always EBUSY, so we need the extra owner
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* variable for assertions.
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*/
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#define ASSERT_NSS_WLOCK_HELD() \
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do { \
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if (__isthreaded) { \
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assert(_pthread_rwlock_trywrlock(&nss_lock) == EBUSY); \
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assert(nss_wlock_owner == _pthread_self()); \
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} \
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} while (0)
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static inline __requires_exclusive(nss_lock) __unlocks(nss_lock) int
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nss_wunlock(void)
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{
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int err;
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ASSERT_NSS_WLOCK_HELD();
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#ifndef NDEBUG
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nss_wlock_owner = NULL;
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#endif
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err = _pthread_rwlock_unlock(&nss_lock);
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assert(err == 0 && "Unlocking should not have failed!");
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return (err);
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}
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/*
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* Runtime determination of whether we are dynamically linked or not.
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@ -114,12 +161,12 @@ const ns_src __nsdefaultsrc[] = {
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};
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/* Database, source mappings. */
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static unsigned int _nsmapsize;
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static ns_dbt *_nsmap = NULL;
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static unsigned int _nsmapsize __guarded_by(nss_lock);
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static ns_dbt *_nsmap __guarded_by(nss_lock);
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/* NSS modules. */
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static unsigned int _nsmodsize;
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static ns_mod *_nsmod;
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static unsigned int _nsmodsize __guarded_by(nss_lock);
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static ns_mod *_nsmod __guarded_by(nss_lock);
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/* Placeholder for builtin modules' dlopen `handle'. */
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static int __nss_builtin_handle;
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@ -166,8 +213,7 @@ typedef int (*vector_comparison)(const void *, const void *);
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typedef void (*vector_free_elem)(void *);
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static void vector_sort(void *, unsigned int, size_t,
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vector_comparison);
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static void vector_free(void *, unsigned int *, size_t,
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vector_free_elem);
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static void _vector_free(void *, unsigned int, size_t, vector_free_elem);
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static void *vector_ref(unsigned int, void *, unsigned int, size_t);
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static void *vector_search(const void *, void *, unsigned int, size_t,
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vector_comparison);
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@ -238,22 +284,24 @@ vector_ref(unsigned int i, void *vec, unsigned int count, size_t esize)
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}
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#define VECTOR_FREE(v, c, s, f) \
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do { vector_free(v, c, s, f); v = NULL; } while (0)
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#define VECTOR_FREE(vec, count, es, fe) do { \
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_vector_free(vec, count, es, fe); \
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vec = NULL; \
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count = 0; \
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} while (0)
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static void
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vector_free(void *vec, unsigned int *count, size_t esize,
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_vector_free(void *vec, unsigned int count, size_t esize,
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vector_free_elem free_elem)
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{
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unsigned int i;
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void *elem;
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for (i = 0; i < *count; i++) {
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elem = vector_ref(i, vec, *count, esize);
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for (i = 0; i < count; i++) {
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elem = vector_ref(i, vec, count, esize);
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if (elem != NULL)
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free_elem(elem);
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}
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free(vec);
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*count = 0;
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}
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/*
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@ -282,13 +330,14 @@ mtab_compare(const void *a, const void *b)
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/*
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* NSS nsmap management.
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*/
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void
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__requires_exclusive(nss_lock) void
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_nsdbtaddsrc(ns_dbt *dbt, const ns_src *src)
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{
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const ns_mod *modp;
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dbt->srclist = vector_append(src, dbt->srclist, &dbt->srclistsize,
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sizeof(*src));
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ASSERT_NSS_WLOCK_HELD();
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dbt->srclist = vector_append(src, dbt->srclist,
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(unsigned int *)&dbt->srclistsize, sizeof(*src));
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modp = vector_search(&src->name, _nsmod, _nsmodsize, sizeof(*_nsmod),
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string_compare);
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if (modp == NULL)
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@ -325,26 +374,28 @@ _nsdbtdump(const ns_dbt *dbt)
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}
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#endif
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#ifndef NS_REREAD_CONF
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static int __guarded_by(nss_lock) already_initialized = 0;
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#endif
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/*
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* The first time nsdispatch is called (during a process's lifetime,
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* or after nsswitch.conf has been updated), nss_configure will
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* prepare global data needed by NSS.
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*/
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static int
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nss_configure(void)
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static __requires_shared(nss_lock) int
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__lock_annotate(no_thread_safety_analysis) /* RWLock upgrade not supported. */
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do_nss_configure(void)
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{
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static time_t confmod;
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static int already_initialized = 0;
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static time_t __guarded_by(nss_lock) confmod = 0;
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struct stat statbuf;
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int result, isthreaded;
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int result;
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const char *path;
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#ifdef NS_CACHING
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void *handle;
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#endif
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result = 0;
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isthreaded = __isthreaded;
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#if defined(_NSS_DEBUG) && defined(_NSS_SHOOT_FOOT)
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/* NOTE WELL: THIS IS A SECURITY HOLE. This must only be built
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* for debugging purposes and MUST NEVER be used in production.
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@ -353,36 +404,33 @@ nss_configure(void)
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if (path == NULL)
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#endif
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path = _PATH_NS_CONF;
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result = _pthread_rwlock_unlock(&nss_lock);
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if (result != 0)
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return (result);
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result = nss_wlock();
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if (result != 0)
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return (result);
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#ifndef NS_REREAD_CONF
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/*
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* Define NS_REREAD_CONF to have nsswitch notice changes
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* to nsswitch.conf(5) during runtime. This involves calling
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* stat(2) every time, which can result in performance hit.
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* Another thread could have already run the initialization
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* logic while we were waiting for the write lock. Check
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* already_initialized to avoid re-initializing.
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*/
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if (already_initialized)
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return (0);
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already_initialized = 1;
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goto fin;
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#endif /* NS_REREAD_CONF */
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ASSERT_NSS_WLOCK_HELD();
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if (stat(path, &statbuf) != 0)
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return (0);
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goto fin;
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if (statbuf.st_mtime <= confmod)
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return (0);
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if (isthreaded) {
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(void)_pthread_rwlock_unlock(&nss_lock);
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result = _pthread_rwlock_wrlock(&nss_lock);
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if (result != 0)
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return (result);
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if (stat(path, &statbuf) != 0)
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goto fin;
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if (statbuf.st_mtime <= confmod)
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goto fin;
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}
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goto fin;
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_nsyyin = fopen(path, "re");
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if (_nsyyin == NULL)
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goto fin;
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VECTOR_FREE(_nsmap, &_nsmapsize, sizeof(*_nsmap),
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VECTOR_FREE(_nsmap, _nsmapsize, sizeof(*_nsmap),
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(vector_free_elem)ns_dbt_free);
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VECTOR_FREE(_nsmod, &_nsmodsize, sizeof(*_nsmod),
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VECTOR_FREE(_nsmod, _nsmodsize, sizeof(*_nsmod),
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(vector_free_elem)ns_mod_free);
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if (confmod == 0)
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(void)atexit(nss_atexit);
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@ -400,22 +448,42 @@ nss_configure(void)
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dlclose(handle);
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}
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#endif
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#ifndef NS_REREAD_CONF
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already_initialized = 1;
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#endif
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fin:
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if (isthreaded) {
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(void)_pthread_rwlock_unlock(&nss_lock);
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if (result == 0)
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result = _pthread_rwlock_rdlock(&nss_lock);
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}
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result = nss_wunlock();
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if (result == 0)
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result = _pthread_rwlock_rdlock(&nss_lock);
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return (result);
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}
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static __requires_shared(nss_lock) int
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nss_configure(void)
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{
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int result;
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#ifndef NS_REREAD_CONF
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/*
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* Define NS_REREAD_CONF to have nsswitch notice changes
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* to nsswitch.conf(5) during runtime. This involves calling
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* stat(2) every time, which can result in performance hit.
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*/
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if (already_initialized)
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return (0);
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#endif /* NS_REREAD_CONF */
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result = do_nss_configure();
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return (result);
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}
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void
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__requires_exclusive(nss_lock) void
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_nsdbtput(const ns_dbt *dbt)
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{
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unsigned int i;
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ns_dbt *p;
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ASSERT_NSS_WLOCK_HELD();
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for (i = 0; i < _nsmapsize; i++) {
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p = vector_ref(i, _nsmap, _nsmapsize, sizeof(*_nsmap));
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if (string_compare(&dbt->name, &p->name) == 0) {
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@ -478,13 +546,15 @@ nss_load_builtin_modules(void)
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* argument is non-NULL, assume a built-in module and use reg_fn to
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* register it. Otherwise, search for a dynamic NSS module.
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*/
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static void
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static __requires_exclusive(nss_lock) void
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nss_load_module(const char *source, nss_module_register_fn reg_fn)
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{
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char buf[PATH_MAX];
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ns_mod mod;
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nss_module_register_fn fn;
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ASSERT_NSS_WLOCK_HELD();
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memset(&mod, 0, sizeof(mod));
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mod.name = strdup(source);
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if (mod.name == NULL) {
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@ -548,9 +618,9 @@ nss_load_module(const char *source, nss_module_register_fn reg_fn)
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vector_sort(_nsmod, _nsmodsize, sizeof(*_nsmod), string_compare);
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}
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static int exiting = 0;
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static int exiting __guarded_by(nss_lock) = 0;
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static void
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static __requires_exclusive(nss_lock) void
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ns_mod_free(ns_mod *mod)
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{
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@ -569,24 +639,19 @@ ns_mod_free(ns_mod *mod)
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static void
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nss_atexit(void)
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{
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int isthreaded;
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(void)nss_wlock();
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exiting = 1;
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isthreaded = __isthreaded;
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if (isthreaded)
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(void)_pthread_rwlock_wrlock(&nss_lock);
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VECTOR_FREE(_nsmap, &_nsmapsize, sizeof(*_nsmap),
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VECTOR_FREE(_nsmap, _nsmapsize, sizeof(*_nsmap),
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(vector_free_elem)ns_dbt_free);
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VECTOR_FREE(_nsmod, &_nsmodsize, sizeof(*_nsmod),
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VECTOR_FREE(_nsmod, _nsmapsize, sizeof(*_nsmod),
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(vector_free_elem)ns_mod_free);
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if (isthreaded)
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(void)_pthread_rwlock_unlock(&nss_lock);
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(void)nss_wunlock();
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}
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/*
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* Finally, the actual implementation.
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*/
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static nss_method
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static __requires_shared(nss_lock) nss_method
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nss_method_lookup(const char *source, const char *database,
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const char *method, const ns_dtab disp_tab[], void **mdata)
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{
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@ -625,7 +690,7 @@ fb_endstate(void *p)
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__weak_reference(_nsdispatch, nsdispatch);
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int
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__requires_unlocked(nss_lock) int
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_nsdispatch(void *retval, const ns_dtab disp_tab[], const char *database,
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const char *method_name, const ns_src defaults[], ...)
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{
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@ -634,7 +699,7 @@ _nsdispatch(void *retval, const ns_dtab disp_tab[], const char *database,
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const ns_src *srclist;
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nss_method method, fb_method;
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void *mdata;
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int isthreaded, serrno, i, result, srclistsize;
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int serrno, i, result, srclistsize;
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struct fb_state *st;
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int saved_depth;
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@ -647,15 +712,8 @@ _nsdispatch(void *retval, const ns_dtab disp_tab[], const char *database,
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dbt = NULL;
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fb_method = NULL;
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isthreaded = __isthreaded;
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serrno = errno;
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if (isthreaded) {
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result = _pthread_rwlock_rdlock(&nss_lock);
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if (result != 0) {
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result = NS_UNAVAIL;
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goto fin;
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}
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}
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(void)_pthread_rwlock_rdlock(&nss_lock);
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result = fb_getstate(&st);
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if (result != 0) {
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@ -774,10 +832,9 @@ _nsdispatch(void *retval, const ns_dtab disp_tab[], const char *database,
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}
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#endif /* NS_CACHING */
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if (isthreaded)
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(void)_pthread_rwlock_unlock(&nss_lock);
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--st->dispatch_depth;
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fin:
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(void)_pthread_rwlock_unlock(&nss_lock);
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errno = serrno;
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return (result);
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}
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