memcpy(x, NULL, 0) is undefined behavior

exosphere/src/i2c.c

@@ -131,7 +131,9 @@ bool i2c_query(unsigned int id, uint8_t device, uint8_t r, void *dst, size_t dst
 /* Writes a value to a register over I2C. */
 bool i2c_send(unsigned int id, uint8_t device, uint8_t r, void *src, size_t src_size) {    
     uint32_t val = r;
-    if (src_size <= 3) {
+    if (src_size == 0) {
+        return true;
+    } else if (src_size <= 3) {
         memcpy(((uint8_t *)&val) + 1, src, src_size);
         return i2c_write(i2c_get_registers_from_id(id), device, &val, src_size + 1);
     } else {
@@ -143,6 +145,8 @@ bool i2c_send(unsigned int id, uint8_t device, uint8_t r, void *src, size_t src_
 bool i2c_write(volatile i2c_registers_t *regs, uint8_t device, void *src, size_t src_size) {
     if (src_size > 4) {
         return false;
+    } else if (src_size == 0) {
+        return true;
     }
 
     /* Set device for 7-bit write mode. */
@@ -172,6 +176,8 @@ bool i2c_write(volatile i2c_registers_t *regs, uint8_t device, void *src, size_t
 bool i2c_read(volatile i2c_registers_t *regs, uint8_t device, void *dst, size_t dst_size) {
     if (dst_size > 4) {
         return false;
+    } else if (dst_size == 0) {
+        return true;
     }
 
     /* Set device for 7-bit read mode. */

exosphere/src/package2.c

@@ -323,9 +323,9 @@ static void load_package2_sections(package2_meta_t *metadata, uint32_t master_ke
         void *src_start = load_buf + sizeof(package2_header_t) + cur_section_offset;
         size_t size = (size_t)metadata->section_sizes[section];
 
-        if (bootconfig_is_package2_plaintext()) {
+        if (bootconfig_is_package2_plaintext() && size != 0) {
             memcpy(dst_start, src_start, size);
-        } else {
+        } else if (size != 0) {
             package2_crypt_ctr(master_key_rev, dst_start, size, src_start, size, metadata->section_ctrs[section], 0x10);
         }
         cur_section_offset += size;

exosphere/src/randomcache.c

@@ -61,7 +61,9 @@ void randomcache_refill(void) {
 
 void randomcache_getbytes(void *dst, size_t num_bytes) {
     unsigned int low = g_random_cache_low;
-    
+    if (num_bytes == 0) {
+        return;
+    }
     memcpy(dst, &g_random_cache[low], num_bytes);
     
     unsigned int new_low = low + num_bytes;

exosphere/src/se.c

@@ -476,7 +476,9 @@ void se_perform_aes_block_operation(void *dst, size_t dst_size, const void *src,
     }
 
     /* Load src data into block. */
+    if (src_size != 0) {
         memcpy(block, src, src_size);
+    }
     flush_dcache_range(block, block + sizeof(block));
 
     /* Trigger AES operation. */
@@ -485,7 +487,9 @@ void se_perform_aes_block_operation(void *dst, size_t dst_size, const void *src,
 
     /* Copy output data into dst. */
     flush_dcache_range(block, block + sizeof(block));
+    if (dst_size != 0) {
         memcpy(dst, block, dst_size);
+    }
 }
 
 void se_aes_ctr_crypt(unsigned int keyslot, void *dst, size_t dst_size, const void *src, size_t src_size, const void *ctr, size_t ctr_size) {
@@ -602,7 +606,6 @@ void se_compute_aes_cmac(unsigned int keyslot, void *cmac, size_t cmac_size, con
     uint8_t last_block[0x10];
     memset(last_block, 0, sizeof(last_block));
     if (data_size & 0xF) {
-
         memcpy(last_block, data + (data_size & ~0xF), data_size & 0xF);
         last_block[data_size & 0xF] = 0x80; /* Last block = data || 100...0 */
     } else if (data_size >= 0x10) {

exosphere/src/smc_user.c

@@ -91,7 +91,9 @@ uint32_t user_get_random_bytes(smc_args_t *args) {
     se_generate_random(KEYSLOT_SWITCH_RNGKEY, random_bytes, size);
     flush_dcache_range(random_bytes, random_bytes + size);
 
+    if (size != 0) {
         memcpy(&args->X[1], random_bytes, size);
+    }
     return 0;
 }
 

exosphere/src/titlekey.c

@@ -34,8 +34,9 @@ void calculate_mgf1_and_xor(void *masked, size_t masked_size, const void *seed,
     }
 
     size_t hash_buf_size = seed_size + 4;
+    if (seed_size != 0) {
         memcpy(hash_buf, seed, seed_size);
-
+    }
     uint32_t round_num = 0;
 
     uint8_t *p_out = (uint8_t *)masked;

exosphere/src/userpage.c

@@ -50,7 +50,9 @@ bool user_copy_to_secure(upage_ref_t *upage, void *secure_dst, void *user_src, s
     }
 
     void *secure_src = (void *)(upage->secure_monitor_address + ((uintptr_t)user_src - upage->user_address));
+    if (size != 0) {
         memcpy(secure_dst, secure_src, size);
+    }
     return true;
 }
 
@@ -66,6 +68,8 @@ bool secure_copy_to_user(upage_ref_t *upage, void *user_dst, void *secure_src, s
     }
 
     void *secure_dst = (void *)(upage->secure_monitor_address + ((uintptr_t)user_dst - upage->user_address));
+    if(size != 0) {
         memcpy(secure_dst, secure_src, size);
+    }
     return true;
 }