MDEV-8799: Server crashes in btr_defragment_add_index, encryption.innodb-bad-key-change5 and alike fail in buildbot

Problem was unsafe access to NULL pointer. Added additional checks to avoid
access to NULL pointer.

6 files changed, 66 insertions, 22 deletions

diff --git a/storage/innobase/btr/btr0cur.cc b/storage/innobase/btr/btr0cur.cc
index 5dbae5d291d..db23b75edf1 100644
--- a/storage/innobase/btr/btr0cur.cc
+++ b/storage/innobase/btr/btr0cur.cc
@@ -1671,15 +1671,24 @@ btr_cur_pessimistic_insert(
 				btr_cur_get_page_zip(cursor),
 				thr_get_trx(thr)->id, mtr);
 		}
-		if (!page_rec_is_infimum(btr_cur_get_rec(cursor))
-		    || btr_page_get_prev(
-			buf_block_get_frame(
-				btr_cur_get_block(cursor)), mtr)
-		       == FIL_NULL) {
+
+		if (!page_rec_is_infimum(btr_cur_get_rec(cursor))) {
 			/* split and inserted need to call
 			lock_update_insert() always. */
 			inherit = TRUE;
 		}
+
+		buf_block_t* block = btr_cur_get_block(cursor);
+		buf_frame_t* frame = NULL;
+
+		if (block) {
+			frame = buf_block_get_frame(block);
+		}
+		/* split and inserted need to call
+		lock_update_insert() always. */
+		if (frame &&  btr_page_get_prev(frame, mtr) == FIL_NULL) {
+			inherit = TRUE;
+		}
 	}
 
 #ifdef BTR_CUR_ADAPT
diff --git a/storage/innobase/btr/btr0defragment.cc b/storage/innobase/btr/btr0defragment.cc
index 30b3a467183..26bab936de5 100644
--- a/storage/innobase/btr/btr0defragment.cc
+++ b/storage/innobase/btr/btr0defragment.cc
@@ -220,8 +220,12 @@ btr_defragment_add_index(
 
 	mtr_start(&mtr);
 	// Load index rood page.
-	page_t* page = btr_page_get(space, zip_size, page_no,
-				    RW_NO_LATCH, index, &mtr);
+	buf_block_t* block = btr_block_get(space, zip_size, page_no, RW_NO_LATCH, index, &mtr);
+	page_t* page = NULL;
+
+	if (block) {
+		page = buf_block_get_frame(block);
+	}
 
 	if (page == NULL && index->table->is_encrypted) {
 		mtr_commit(&mtr);
diff --git a/storage/innobase/btr/btr0scrub.cc b/storage/innobase/btr/btr0scrub.cc
index d53b478e429..e6acb7802f1 100644
--- a/storage/innobase/btr/btr0scrub.cc
+++ b/storage/innobase/btr/btr0scrub.cc
@@ -750,9 +750,13 @@ btr_scrub_page(
 	mtr_t* mtr)               /*!< in: mtr */
 {
 	/* recheck if page needs scrubbing (knowing allocation status) */
-	int needs_scrubbing = btr_page_needs_scrubbing(
-		scrub_data, block, allocated);
-	if (needs_scrubbing != BTR_SCRUB_PAGE) {
+	int needs_scrubbing = BTR_SCRUB_SKIP_PAGE_AND_CLOSE_TABLE;
+
+	if (block) {
+		btr_page_needs_scrubbing(scrub_data, block, allocated);
+	}
+
+	if (!block || needs_scrubbing != BTR_SCRUB_PAGE) {
 		mtr_commit(mtr);
 		return needs_scrubbing;
 	}
@@ -784,7 +788,12 @@ btr_scrub_page(
 		return BTR_SCRUB_SKIP_PAGE_AND_CLOSE_TABLE;
 	}
 
-	if (btr_page_get_index_id(buf_block_get_frame(block)) !=
+	buf_frame_t* frame = NULL;
+
+	if (block) {
+		frame = buf_block_get_frame(block);
+	}
+	if (!frame || btr_page_get_index_id(frame) !=
 	    scrub_data->current_index->id) {
 		/* page has been reallocated to new index */
 		mtr_commit(mtr);
diff --git a/storage/xtradb/btr/btr0cur.cc b/storage/xtradb/btr/btr0cur.cc
index 728d14e6309..44b0e50fa0f 100644
--- a/storage/xtradb/btr/btr0cur.cc
+++ b/storage/xtradb/btr/btr0cur.cc
@@ -1795,15 +1795,24 @@ btr_cur_pessimistic_insert(
 				btr_cur_get_page_zip(cursor),
 				thr_get_trx(thr)->id, mtr);
 		}
-		if (!page_rec_is_infimum(btr_cur_get_rec(cursor))
-		    || btr_page_get_prev(
-			buf_block_get_frame(
-				btr_cur_get_block(cursor)), mtr)
-		       == FIL_NULL) {
+
+		if (!page_rec_is_infimum(btr_cur_get_rec(cursor))) {
 			/* split and inserted need to call
 			lock_update_insert() always. */
 			inherit = TRUE;
 		}
+
+		buf_block_t* block = btr_cur_get_block(cursor);
+		buf_frame_t* frame = NULL;
+
+		if (block) {
+			frame = buf_block_get_frame(block);
+		}
+		/* split and inserted need to call
+		lock_update_insert() always. */
+		if (frame &&  btr_page_get_prev(frame, mtr) == FIL_NULL) {
+			inherit = TRUE;
+		}
 	}
 
 #ifdef BTR_CUR_ADAPT
diff --git a/storage/xtradb/btr/btr0defragment.cc b/storage/xtradb/btr/btr0defragment.cc
index 7f502eb5084..6e7a3fd2411 100644
--- a/storage/xtradb/btr/btr0defragment.cc
+++ b/storage/xtradb/btr/btr0defragment.cc
@@ -220,8 +220,12 @@ btr_defragment_add_index(
 
 	mtr_start(&mtr);
 	// Load index rood page.
-	page_t* page = btr_page_get(space, zip_size, page_no,
-				    RW_NO_LATCH, index, &mtr);
+	buf_block_t* block = btr_block_get(space, zip_size, page_no, RW_NO_LATCH, index, &mtr);
+	page_t* page = NULL;
+
+	if (block) {
+		page = buf_block_get_frame(block);
+	}
 
 	if (page == NULL && index->table->is_encrypted) {
 		mtr_commit(&mtr);
diff --git a/storage/xtradb/btr/btr0scrub.cc b/storage/xtradb/btr/btr0scrub.cc
index d53b478e429..e6acb7802f1 100644
--- a/storage/xtradb/btr/btr0scrub.cc
+++ b/storage/xtradb/btr/btr0scrub.cc
@@ -750,9 +750,13 @@ btr_scrub_page(
 	mtr_t* mtr)               /*!< in: mtr */
 {
 	/* recheck if page needs scrubbing (knowing allocation status) */
-	int needs_scrubbing = btr_page_needs_scrubbing(
-		scrub_data, block, allocated);
-	if (needs_scrubbing != BTR_SCRUB_PAGE) {
+	int needs_scrubbing = BTR_SCRUB_SKIP_PAGE_AND_CLOSE_TABLE;
+
+	if (block) {
+		btr_page_needs_scrubbing(scrub_data, block, allocated);
+	}
+
+	if (!block || needs_scrubbing != BTR_SCRUB_PAGE) {
 		mtr_commit(mtr);
 		return needs_scrubbing;
 	}
@@ -784,7 +788,12 @@ btr_scrub_page(
 		return BTR_SCRUB_SKIP_PAGE_AND_CLOSE_TABLE;
 	}
 
-	if (btr_page_get_index_id(buf_block_get_frame(block)) !=
+	buf_frame_t* frame = NULL;
+
+	if (block) {
+		frame = buf_block_get_frame(block);
+	}
+	if (!frame || btr_page_get_index_id(frame) !=
 	    scrub_data->current_index->id) {
 		/* page has been reallocated to new index */
 		mtr_commit(mtr);