pstore fixes for v5.2-rc4

- Avoid NULL deref when unloading/reloading ramoops module (Pi-Hsun Shih)
 - Run ramoops without crash dump region
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 Comment: Kees Cook <kees@outflux.net>
 
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Merge tag 'pstore-v5.2-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux

Pull pstore fixes from Kees Cook:

 - Avoid NULL deref when unloading/reloading ramoops module (Pi-Hsun
   Shih)

 - Run ramoops without crash dump region

* tag 'pstore-v5.2-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux:
  pstore/ram: Run without kernel crash dump region
  pstore: Set tfm to NULL on free_buf_for_compression

fs/pstore/platform.c

@@ -347,8 +347,10 @@ static void allocate_buf_for_compression(void)
 
 static void free_buf_for_compression(void)
 {
-	if (IS_ENABLED(CONFIG_PSTORE_COMPRESS) && tfm)
+	if (IS_ENABLED(CONFIG_PSTORE_COMPRESS) && tfm) {
 		crypto_free_comp(tfm);
+		tfm = NULL;
+	}
 	kfree(big_oops_buf);
 	big_oops_buf = NULL;
 	big_oops_buf_sz = 0;
@@ -606,7 +608,8 @@ int pstore_register(struct pstore_info *psi)
 		return -EINVAL;
 	}
 
-	allocate_buf_for_compression();
+	if (psi->flags & PSTORE_FLAGS_DMESG)
+		allocate_buf_for_compression();
 
 	if (pstore_is_mounted())
 		pstore_get_records(0);

fs/pstore/ram.c

@@ -799,27 +799,37 @@ static int ramoops_probe(struct platform_device *pdev)
 		goto fail_init_mprz;
 
 	cxt->pstore.data = cxt;
+	/*
+	 * Prepare frontend flags based on which areas are initialized.
+	 * For ramoops_init_przs() cases, the "max count" variable tells
+	 * if there are regions present. For ramoops_init_prz() cases,
+	 * the single region size is how to check.
+	 */
+	cxt->pstore.flags = 0;
+	if (cxt->max_dump_cnt)
+		cxt->pstore.flags |= PSTORE_FLAGS_DMESG;
+	if (cxt->console_size)
+		cxt->pstore.flags |= PSTORE_FLAGS_CONSOLE;
+	if (cxt->max_ftrace_cnt)
+		cxt->pstore.flags |= PSTORE_FLAGS_FTRACE;
+	if (cxt->pmsg_size)
+		cxt->pstore.flags |= PSTORE_FLAGS_PMSG;
+
 	/*
 	 * Since bufsize is only used for dmesg crash dumps, it
 	 * must match the size of the dprz record (after PRZ header
 	 * and ECC bytes have been accounted for).
 	 */
-	cxt->pstore.bufsize = cxt->dprzs[0]->buffer_size;
-	cxt->pstore.buf = kzalloc(cxt->pstore.bufsize, GFP_KERNEL);
-	if (!cxt->pstore.buf) {
-		pr_err("cannot allocate pstore crash dump buffer\n");
-		err = -ENOMEM;
-		goto fail_clear;
+	if (cxt->pstore.flags & PSTORE_FLAGS_DMESG) {
+		cxt->pstore.bufsize = cxt->dprzs[0]->buffer_size;
+		cxt->pstore.buf = kzalloc(cxt->pstore.bufsize, GFP_KERNEL);
+		if (!cxt->pstore.buf) {
+			pr_err("cannot allocate pstore crash dump buffer\n");
+			err = -ENOMEM;
+			goto fail_clear;
+		}
 	}
 
-	cxt->pstore.flags = PSTORE_FLAGS_DMESG;
-	if (cxt->console_size)
-		cxt->pstore.flags |= PSTORE_FLAGS_CONSOLE;
-	if (cxt->ftrace_size)
-		cxt->pstore.flags |= PSTORE_FLAGS_FTRACE;
-	if (cxt->pmsg_size)
-		cxt->pstore.flags |= PSTORE_FLAGS_PMSG;
-
 	err = pstore_register(&cxt->pstore);
 	if (err) {
 		pr_err("registering with pstore failed\n");