pstore/ram: Add check for kstrdup

Add check for the return value of kstrdup() and return the error
if it fails in order to avoid NULL pointer dereference.

Fixes: e163fdb3 ("pstore/ram: Regularize prz label allocation lifetime")
Signed-off-by: Jiasheng Jiang <jiasheng@iscas.ac.cn>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20230614093733.36048-1-jiasheng@iscas.ac.cn

fs/pstore/ram_core.c

@@ -599,6 +599,8 @@ struct persistent_ram_zone *persistent_ram_new(phys_addr_t start, size_t size,
 	raw_spin_lock_init(&prz->buffer_lock);
 	prz->flags = flags;
 	prz->label = kstrdup(label, GFP_KERNEL);
+	if (!prz->label)
+		goto err;
 
 	ret = persistent_ram_buffer_map(start, size, prz, memtype);
 	if (ret)