diff mbox series

[v3,1/2] riscv: Safely remove entries from relocation list

Message ID 20231122-module_linking_freeing-v3-1-8e9e412a3305@rivosinc.com
State New
Headers
Series riscv: Fix issues with module loading |

Commit Message

Charlie Jenkins Nov. 22, 2023, 11:31 p.m. UTC 
  Use the safe versions of list and hlist iteration to safely remove
entries from the module relocation lists. To allow mutliple threads to
load modules concurrently, move relocation list pointers onto the stack
rather than using global variables.

Fixes: 8fd6c5142395 ("riscv: Add remaining module relocations")
Reported-by: Ron Economos <re@w6rz.net>
Closes: https://lore.kernel.org/linux-riscv/444de86a-7e7c-4de7-5d1d-c1c40eefa4ba@w6rz.net
Signed-off-by: Charlie Jenkins <charlie@rivosinc.com>
---
 arch/riscv/kernel/module.c | 93 ++++++++++++++++++++++++++++++++++------------
 1 file changed, 69 insertions(+), 24 deletions(-)

Comments

Andreas Schwab Nov. 27, 2023, 10:42 a.m. UTC | #1 
On Nov 22 2023, Charlie Jenkins wrote:

> @@ -683,17 +700,29 @@ int add_relocation_to_accumulate(struct module *me, int type, void *location,
>  
>  	if (!found) {
>  		rel_head = kmalloc(sizeof(*rel_head), GFP_KERNEL);
> +
> +		if (!rel_head)
> +			return -ENOMEM;
> +
>  		rel_head->rel_entry =
>  			kmalloc(sizeof(struct list_head), GFP_KERNEL);
> +
> +		if (!rel_head->rel_entry)
> +			return -ENOMEM;

This leaks rel_head on error.
Charlie Jenkins Dec. 4, 2023, 6:42 p.m. UTC | #2 
On Mon, Nov 27, 2023 at 11:42:08AM +0100, Andreas Schwab wrote:
> On Nov 22 2023, Charlie Jenkins wrote:
> 
> > @@ -683,17 +700,29 @@ int add_relocation_to_accumulate(struct module *me, int type, void *location,
> >  
> >  	if (!found) {
> >  		rel_head = kmalloc(sizeof(*rel_head), GFP_KERNEL);
> > +
> > +		if (!rel_head)
> > +			return -ENOMEM;
> > +
> >  		rel_head->rel_entry =
> >  			kmalloc(sizeof(struct list_head), GFP_KERNEL);
> > +
> > +		if (!rel_head->rel_entry)
> > +			return -ENOMEM;
> 
> This leaks rel_head on error.
> 
> -- 
> Andreas Schwab, schwab@linux-m68k.org
> GPG Key fingerprint = 7578 EB47 D4E5 4D69 2510  2552 DF73 E780 A9DA AEC1
> "And now for something completely different."

Thank you for pointing this out, I fixed this issue in the next version
but forgot to respond to this thread.

https://lore.kernel.org/linux-riscv/20231127-module_linking_freeing-v4-1-a2ca1d7027d0@rivosinc.com/

- Charlie
diff mbox series

Patch

diff --git a/arch/riscv/kernel/module.c b/arch/riscv/kernel/module.c
index 56a8c78e9e21..fd9a5533518c 100644
--- a/arch/riscv/kernel/module.c
+++ b/arch/riscv/kernel/module.c
@@ -40,14 +40,16 @@  struct relocation_handlers {
 				  long buffer);
 };
 
-unsigned int initialize_relocation_hashtable(unsigned int num_relocations);
-void process_accumulated_relocations(struct module *me);
+unsigned int
+initialize_relocation_hashtable(unsigned int num_relocations,
+				struct hlist_head **relocation_hashtable);
+void process_accumulated_relocations(struct module *me,
+				     struct hlist_head **relocation_hashtable,
+				     struct list_head *used_buckets_list);
 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;
+				 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
@@ -604,7 +606,9 @@  static const struct relocation_handlers reloc_handlers[] = {
 	/* 192-255 nonstandard ABI extensions  */
 };
 
-void process_accumulated_relocations(struct module *me)
+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 +628,25 @@  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 +659,13 @@  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)
+				 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 +674,10 @@  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;
@@ -683,17 +700,29 @@  int add_relocation_to_accumulate(struct module *me, int type, void *location,
 
 	if (!found) {
 		rel_head = kmalloc(sizeof(*rel_head), GFP_KERNEL);
+
+		if (!rel_head)
+			return -ENOMEM;
+
 		rel_head->rel_entry =
 			kmalloc(sizeof(struct list_head), GFP_KERNEL);
+
+		if (!rel_head->rel_entry)
+			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)
+				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 +733,9 @@  int add_relocation_to_accumulate(struct module *me, int type, void *location,
 	return 0;
 }
 
-unsigned int initialize_relocation_hashtable(unsigned int num_relocations)
+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 +751,13 @@  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 +774,17 @@  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 +865,17 @@  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;
 }