Fix context locking

Some parts of OPENSSL_CTX intialisation can get quite complex (e.g. RAND).
This can lead to complex interactions where different parts of the library
try to initialise while other parts are still initialising. This can lead
to deadlocks because both parts want to obtain the init lock.

We separate out the init lock so that it is only used to manage the
dynamic list of indexes. Each part of the library gets its own
initialisation lock.

Fixes #9454

Reviewed-by: Paul Dale <paul.dale@oracle.com>
Reviewed-by: Richard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/9590)

1 files changed, 38 insertions, 4 deletions

diff --git a/crypto/context.c b/crypto/context.c
index cc1ec0e664..ad4e997a7c 100644
--- a/crypto/context.c
+++ b/crypto/context.c
@@ -28,6 +28,9 @@ struct openssl_ctx_st {
     /* Map internal static indexes to dynamically created indexes */
     int dyn_indexes[OPENSSL_CTX_MAX_INDEXES];
 
+    /* Keep a separate lock for each index */
+    CRYPTO_RWLOCK *index_locks[OPENSSL_CTX_MAX_INDEXES];
+
     CRYPTO_RWLOCK *oncelock;
     int run_once_done[OPENSSL_CTX_MAX_RUN_ONCE];
     int run_once_ret[OPENSSL_CTX_MAX_RUN_ONCE];
@@ -53,8 +56,12 @@ static int context_init(OPENSSL_CTX *ctx)
     if (ctx->oncelock == NULL)
         goto err;
 
-    for (i = 0; i < OPENSSL_CTX_MAX_INDEXES; i++)
+    for (i = 0; i < OPENSSL_CTX_MAX_INDEXES; i++) {
+        ctx->index_locks[i] = CRYPTO_THREAD_lock_new();
         ctx->dyn_indexes[i] = -1;
+        if (ctx->index_locks[i] == NULL)
+            goto err;
+    }
 
     if (!do_ex_data_init(ctx))
         goto err;
@@ -76,6 +83,7 @@ static int context_init(OPENSSL_CTX *ctx)
 static int context_deinit(OPENSSL_CTX *ctx)
 {
     struct openssl_ctx_onfree_list_st *tmp, *onfree;
+    int i;
 
     if (ctx == NULL)
         return 1;
@@ -91,6 +99,9 @@ static int context_deinit(OPENSSL_CTX *ctx)
     }
     CRYPTO_free_ex_data(CRYPTO_EX_INDEX_OPENSSL_CTX, NULL, &ctx->data);
     crypto_cleanup_all_ex_data_int(ctx);
+    for (i = 0; i < OPENSSL_CTX_MAX_INDEXES; i++)
+        CRYPTO_THREAD_lock_free(ctx->index_locks[i]);
+
     CRYPTO_THREAD_lock_free(ctx->oncelock);
     CRYPTO_THREAD_lock_free(ctx->lock);
     ctx->lock = NULL;
@@ -187,25 +198,48 @@ void *openssl_ctx_get_data(OPENSSL_CTX *ctx, int index,
                            const OPENSSL_CTX_METHOD *meth)
 {
     void *data = NULL;
+    int dynidx;
 
     ctx = openssl_ctx_get_concrete(ctx);
     if (ctx == NULL)
         return NULL;
 
     CRYPTO_THREAD_read_lock(ctx->lock);
+    dynidx = ctx->dyn_indexes[index];
+    CRYPTO_THREAD_unlock(ctx->lock);
+
+    if (dynidx != -1) {
+        CRYPTO_THREAD_read_lock(ctx->index_locks[index]);
+        data = CRYPTO_get_ex_data(&ctx->data, dynidx);
+        CRYPTO_THREAD_unlock(ctx->index_locks[index]);
+        return data;
+    }
 
-    if (ctx->dyn_indexes[index] == -1
-            && !openssl_ctx_init_index(ctx, index, meth)) {
+    CRYPTO_THREAD_write_lock(ctx->index_locks[index]);
+    CRYPTO_THREAD_write_lock(ctx->lock);
+
+    dynidx = ctx->dyn_indexes[index];
+    if (dynidx != -1) {
+        CRYPTO_THREAD_unlock(ctx->lock);
+        data = CRYPTO_get_ex_data(&ctx->data, dynidx);
+        CRYPTO_THREAD_unlock(ctx->index_locks[index]);
+        return data;
+    }
+
+    if (!openssl_ctx_init_index(ctx, index, meth)) {
         CRYPTO_THREAD_unlock(ctx->lock);
+        CRYPTO_THREAD_unlock(ctx->index_locks[index]);
         return NULL;
     }
 
+    CRYPTO_THREAD_unlock(ctx->lock);
+
     /* The alloc call ensures there's a value there */
     if (CRYPTO_alloc_ex_data(CRYPTO_EX_INDEX_OPENSSL_CTX, NULL,
                              &ctx->data, ctx->dyn_indexes[index]))
         data = CRYPTO_get_ex_data(&ctx->data, ctx->dyn_indexes[index]);
 
-    CRYPTO_THREAD_unlock(ctx->lock);
+    CRYPTO_THREAD_unlock(ctx->index_locks[index]);
 
     return data;
 }