Merge patch series "riscv: Fix issues with module loading"

Charlie Jenkins <charlie@rivosinc.com> says:

Module loading did not account for multiple threads concurrently loading
modules. This patch fixes that issue. There is also a small patch to fix
the type of a __le16 variable.

* b4-shazam-merge:
  riscv: Correct type casting in module loading
  riscv: Safely remove entries from relocation list

Link: https://lore.kernel.org/r/20231127-module_linking_freeing-v4-0-a2ca1d7027d0@rivosinc.comSigned-off-by: Palmer Dabbelt <palmer@rivosinc.com>

arch/riscv/kernel/module.c

@@ -40,15 +40,6 @@ struct relocation_handlers {
 				  long buffer);
 };
 
-unsigned int initialize_relocation_hashtable(unsigned int num_relocations);
-void process_accumulated_relocations(struct module *me);
-int add_relocation_to_accumulate(struct module *me, int type, void *location,
-				 unsigned int hashtable_bits, Elf_Addr v);
-
-struct hlist_head *relocation_hashtable;
-
-struct list_head used_buckets_list;
-
 /*
  * The auipc+jalr instruction pair can reach any PC-relative offset
  * in the range [-2^31 - 2^11, 2^31 - 2^11)
@@ -64,7 +55,7 @@ static bool riscv_insn_valid_32bit_offset(ptrdiff_t val)
 
 static int riscv_insn_rmw(void *location, u32 keep, u32 set)
 {
-	u16 *parcel = location;
+	__le16 *parcel = location;
 	u32 insn = (u32)le16_to_cpu(parcel[0]) | (u32)le16_to_cpu(parcel[1]) << 16;
 
 	insn &= keep;
@@ -77,7 +68,7 @@ static int riscv_insn_rmw(void *location, u32 keep, u32 set)
 
 static int riscv_insn_rvc_rmw(void *location, u16 keep, u16 set)
 {
-	u16 *parcel = location;
+	__le16 *parcel = location;
 	u16 insn = le16_to_cpu(*parcel);
 
 	insn &= keep;
@@ -604,7 +595,10 @@ static const struct relocation_handlers reloc_handlers[] = {
 	/* 192-255 nonstandard ABI extensions  */
 };
 
-void process_accumulated_relocations(struct module *me)
+static void
+process_accumulated_relocations(struct module *me,
+				struct hlist_head **relocation_hashtable,
+				struct list_head *used_buckets_list)
 {
 	/*
 	 * Only ADD/SUB/SET/ULEB128 should end up here.
@@ -624,18 +618,25 @@ void process_accumulated_relocations(struct module *me)
 	 *	- Each relocation entry for a location address
 	 */
 	struct used_bucket *bucket_iter;
+	struct used_bucket *bucket_iter_tmp;
 	struct relocation_head *rel_head_iter;
+	struct hlist_node *rel_head_iter_tmp;
 	struct relocation_entry *rel_entry_iter;
+	struct relocation_entry *rel_entry_iter_tmp;
 	int curr_type;
 	void *location;
 	long buffer;
 
-	list_for_each_entry(bucket_iter, &used_buckets_list, head) {
-		hlist_for_each_entry(rel_head_iter, bucket_iter->bucket, node) {
+	list_for_each_entry_safe(bucket_iter, bucket_iter_tmp,
+				 used_buckets_list, head) {
+		hlist_for_each_entry_safe(rel_head_iter, rel_head_iter_tmp,
+					  bucket_iter->bucket, node) {
 			buffer = 0;
 			location = rel_head_iter->location;
-			list_for_each_entry(rel_entry_iter,
-					    rel_head_iter->rel_entry, head) {
+			list_for_each_entry_safe(rel_entry_iter,
+						 rel_entry_iter_tmp,
+						 rel_head_iter->rel_entry,
+						 head) {
 				curr_type = rel_entry_iter->type;
 				reloc_handlers[curr_type].reloc_handler(
 					me, &buffer, rel_entry_iter->value);
@@ -648,11 +649,14 @@ void process_accumulated_relocations(struct module *me)
 		kfree(bucket_iter);
 	}
 
-	kfree(relocation_hashtable);
+	kfree(*relocation_hashtable);
 }
 
-int add_relocation_to_accumulate(struct module *me, int type, void *location,
-				 unsigned int hashtable_bits, Elf_Addr v)
+static int add_relocation_to_accumulate(struct module *me, int type,
+					void *location,
+					unsigned int hashtable_bits, Elf_Addr v,
+					struct hlist_head *relocation_hashtable,
+					struct list_head *used_buckets_list)
 {
 	struct relocation_entry *entry;
 	struct relocation_head *rel_head;
@@ -661,6 +665,10 @@ int add_relocation_to_accumulate(struct module *me, int type, void *location,
 	unsigned long hash;
 
 	entry = kmalloc(sizeof(*entry), GFP_KERNEL);
+
+	if (!entry)
+		return -ENOMEM;
+
 	INIT_LIST_HEAD(&entry->head);
 	entry->type = type;
 	entry->value = v;
@@ -669,7 +677,10 @@ int add_relocation_to_accumulate(struct module *me, int type, void *location,
 
 	current_head = &relocation_hashtable[hash];
 
-	/* Find matching location (if any) */
+	/*
+	 * Search for the relocation_head for the relocations that happen at the
+	 * provided location
+	 */
 	bool found = false;
 	struct relocation_head *rel_head_iter;
 
@@ -681,19 +692,45 @@ int add_relocation_to_accumulate(struct module *me, int type, void *location,
 		}
 	}
 
+	/*
+	 * If there has not yet been any relocations at the provided location,
+	 * create a relocation_head for that location and populate it with this
+	 * relocation_entry.
+	 */
 	if (!found) {
 		rel_head = kmalloc(sizeof(*rel_head), GFP_KERNEL);
+
+		if (!rel_head) {
+			kfree(entry);
+			return -ENOMEM;
+		}
+
 		rel_head->rel_entry =
 			kmalloc(sizeof(struct list_head), GFP_KERNEL);
+
+		if (!rel_head->rel_entry) {
+			kfree(entry);
+			kfree(rel_head);
+			return -ENOMEM;
+		}
+
 		INIT_LIST_HEAD(rel_head->rel_entry);
 		rel_head->location = location;
 		INIT_HLIST_NODE(&rel_head->node);
 		if (!current_head->first) {
 			bucket =
 				kmalloc(sizeof(struct used_bucket), GFP_KERNEL);
+
+			if (!bucket) {
+				kfree(entry);
+				kfree(rel_head);
+				kfree(rel_head->rel_entry);
+				return -ENOMEM;
+			}
+
 			INIT_LIST_HEAD(&bucket->head);
 			bucket->bucket = current_head;
-			list_add(&bucket->head, &used_buckets_list);
+			list_add(&bucket->head, used_buckets_list);
 		}
 		hlist_add_head(&rel_head->node, current_head);
 	}
@@ -704,7 +741,9 @@ int add_relocation_to_accumulate(struct module *me, int type, void *location,
 	return 0;
 }
 
-unsigned int initialize_relocation_hashtable(unsigned int num_relocations)
+static unsigned int
+initialize_relocation_hashtable(unsigned int num_relocations,
+				struct hlist_head **relocation_hashtable)
 {
 	/* Can safely assume that bits is not greater than sizeof(long) */
 	unsigned long hashtable_size = roundup_pow_of_two(num_relocations);
@@ -720,12 +759,13 @@ unsigned int initialize_relocation_hashtable(unsigned int num_relocations)
 
 	hashtable_size <<= should_double_size;
 
-	relocation_hashtable = kmalloc_array(hashtable_size,
-					     sizeof(*relocation_hashtable),
-					     GFP_KERNEL);
-	__hash_init(relocation_hashtable, hashtable_size);
+	*relocation_hashtable = kmalloc_array(hashtable_size,
+					      sizeof(*relocation_hashtable),
+					      GFP_KERNEL);
+	if (!*relocation_hashtable)
+		return -ENOMEM;
 
-	INIT_LIST_HEAD(&used_buckets_list);
+	__hash_init(*relocation_hashtable, hashtable_size);
 
 	return hashtable_bits;
 }
@@ -742,7 +782,17 @@ int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
 	Elf_Addr v;
 	int res;
 	unsigned int num_relocations = sechdrs[relsec].sh_size / sizeof(*rel);
-	unsigned int hashtable_bits = initialize_relocation_hashtable(num_relocations);
+	struct hlist_head *relocation_hashtable;
+	struct list_head used_buckets_list;
+	unsigned int hashtable_bits;
+
+	hashtable_bits = initialize_relocation_hashtable(num_relocations,
+							 &relocation_hashtable);
+
+	if (hashtable_bits < 0)
+		return hashtable_bits;
+
+	INIT_LIST_HEAD(&used_buckets_list);
 
 	pr_debug("Applying relocate section %u to %u\n", relsec,
 	       sechdrs[relsec].sh_info);
@@ -823,14 +873,18 @@ int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
 		}
 
 		if (reloc_handlers[type].accumulate_handler)
-			res = add_relocation_to_accumulate(me, type, location, hashtable_bits, v);
+			res = add_relocation_to_accumulate(me, type, location,
+							   hashtable_bits, v,
+							   relocation_hashtable,
+							   &used_buckets_list);
 		else
 			res = handler(me, location, v);
 		if (res)
 			return res;
 	}
 
-	process_accumulated_relocations(me);
+	process_accumulated_relocations(me, &relocation_hashtable,
+					&used_buckets_list);
 
 	return 0;
 }