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Mon, 27 Nov 2023 14:05:16 -0800 (PST) From: Charlie Jenkins Date: Mon, 27 Nov 2023 14:04:59 -0800 Subject: [PATCH v4 1/2] riscv: Safely remove entries from relocation list MIME-Version: 1.0 Message-Id: <20231127-module_linking_freeing-v4-1-a2ca1d7027d0@rivosinc.com> References: <20231127-module_linking_freeing-v4-0-a2ca1d7027d0@rivosinc.com> In-Reply-To: <20231127-module_linking_freeing-v4-0-a2ca1d7027d0@rivosinc.com> To: Paul Walmsley , Palmer Dabbelt , Albert Ou , Ron Economos , Samuel Holland , Andreas Schwab Cc: linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, Charlie Jenkins X-Mailer: b4 0.12.3 X-Developer-Signature: v=1; a=ed25519-sha256; t=1701122714; l=7889; i=charlie@rivosinc.com; s=20231120; h=from:subject:message-id; bh=oWHW0TwoEipPebbTedSb6UcR9/YptErZBNQ3JSBym2M=; b=J5XMWA4G1aZEqzAa6mZIwB3AtKNSf780SvwoUHh01Oa9Q5isHKUpK6W2FqqHwdQoqVDzg7SH4 N7r+wwuHq2TA6ly2xMZb23IDdNT8rKFQ9sZX+tbiCNwdqUw6gwDZ6QI X-Developer-Key: i=charlie@rivosinc.com; a=ed25519; pk=t4RSWpMV1q5lf/NWIeR9z58bcje60/dbtxxmoSfBEcs= X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,RCVD_IN_DNSWL_BLOCKED,SPF_HELO_NONE,SPF_PASS, T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-Greylist: Sender passed SPF test, not delayed by milter-greylist-4.6.4 (snail.vger.email [0.0.0.0]); Mon, 27 Nov 2023 14:05:26 -0800 (PST) X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1783756509274642121 X-GMAIL-MSGID: 1783756509274642121 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 Closes: https://lore.kernel.org/linux-riscv/444de86a-7e7c-4de7-5d1d-c1c40eefa4ba@w6rz.net Signed-off-by: Charlie Jenkins Tested-by: Lad Prabhakar #On --- arch/riscv/kernel/module.c | 110 +++++++++++++++++++++++++++++++++------------ 1 file changed, 82 insertions(+), 28 deletions(-) diff --git a/arch/riscv/kernel/module.c b/arch/riscv/kernel/module.c index 56a8c78e9e21..53593fe58cd8 100644 --- a/arch/riscv/kernel/module.c +++ b/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) @@ -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; }