Add ASAP abort flag to provisional primary for safer replication disc…

…onnection handling

Introduces a dedicated flag in provisional primary struct to signal immediate
abort, preventing potential use-after-free scenarios during replication
disconnection in dual-channel load. This ensures proper termination of
rdbLoadRioWithLoadingCtx when replication is cancelled due to connection loss
on main connection.

Fixes #1152

Signed-off-by: naglera <anagler123@gmail.com>

src/rdb.c

@@ -2921,7 +2921,7 @@ void stopSaving(int success) {
 
 /* Track loading progress in order to serve client's from time to time
    and if needed calculate rdb checksum  */
-void rdbLoadProgressCallback(rio *r, const void *buf, size_t len) {
+int rdbLoadProgressCallback(rio *r, const void *buf, size_t len) {
     if (server.rdb_checksum) rioGenericUpdateChecksum(r, buf, len);
     if (server.loading_process_events_interval_bytes &&
         (r->processed_bytes + len) / server.loading_process_events_interval_bytes >
@@ -2934,6 +2934,11 @@ void rdbLoadProgressCallback(rio *r, const void *buf, size_t len) {
     if (server.repl_state == REPL_STATE_TRANSFER && rioCheckType(r) == RIO_TYPE_CONN) {
         server.stat_net_repl_input_bytes += len;
     }
+    if (server.repl_provisional_primary.close_asap == 1) {
+        serverLog(LL_WARNING, "Primary main connection dropped during RDB load callback");
+        return -1;
+    }
+    return 0;
 }
 
 /* Save the given functions_ctx to the rdb.

src/replication.c

@@ -2701,6 +2701,7 @@ static int dualChannelReplHandleEndOffsetResponse(connection *conn, sds *err) {
     server.repl_provisional_primary.reploff = reploffset;
     server.repl_provisional_primary.read_reploff = reploffset;
     server.repl_provisional_primary.dbid = dbid;
+    server.repl_provisional_primary.close_asap = 0;
 
     /* Now that we have the snapshot end-offset, we can ask for psync from that offset. Prepare the
      * main connection accordingly.*/
@@ -2833,6 +2834,7 @@ int readIntoReplDataBlock(connection *conn, replDataBufBlock *data_block, size_t
     }
     if (nread == 0) {
         serverLog(LL_VERBOSE, "Provisional primary closed connection");
+        server.repl_provisional_primary.close_asap = 1;
         cancelReplicationHandshake(1);
         return C_ERR;
     }

src/rio.c

@@ -424,8 +424,9 @@ void rioFreeFd(rio *r) {
 
 /* This function can be installed both in memory and file streams when checksum
  * computation is needed. */
-void rioGenericUpdateChecksum(rio *r, const void *buf, size_t len) {
+int rioGenericUpdateChecksum(rio *r, const void *buf, size_t len) {
     r->cksum = crc64(r->cksum, buf, len);
+    return 1;
 }
 
 /* Set the file-based rio object to auto-fsync every 'bytes' file written.

src/rio.h

@@ -57,8 +57,10 @@ struct _rio {
      * all the data that was read or written so far. The method should be
      * designed so that can be called with the current checksum, and the buf
      * and len fields pointing to the new block of data to add to the checksum
-     * computation. */
-    void (*update_cksum)(struct _rio *, const void *buf, size_t len);
+     * computation. 
+     * The method should return -1 to indicate that the rio operation should be
+     * terminated, or a non-negative value to continue processing. */
+    int (*update_cksum)(struct _rio *, const void *buf, size_t len);
 
     /* The current checksum and flags (see RIO_FLAG_*) */
     uint64_t cksum, flags;
@@ -140,7 +142,7 @@ static inline size_t rioRead(rio *r, void *buf, size_t len) {
             r->flags |= RIO_FLAG_READ_ERROR;
             return 0;
         }
-        if (r->update_cksum) r->update_cksum(r, buf, bytes_to_read);
+        if (r->update_cksum && r->update_cksum(r, buf, bytes_to_read) < 0) return 0;
         buf = (char *)buf + bytes_to_read;
         len -= bytes_to_read;
         r->processed_bytes += bytes_to_read;
@@ -188,7 +190,7 @@ size_t rioWriteBulkDouble(rio *r, double d);
 struct serverObject;
 int rioWriteBulkObject(rio *r, struct serverObject *obj);
 
-void rioGenericUpdateChecksum(rio *r, const void *buf, size_t len);
+int rioGenericUpdateChecksum(rio *r, const void *buf, size_t len);
 void rioSetAutoSync(rio *r, off_t bytes);
 void rioSetReclaimCache(rio *r, int enabled);
 uint8_t rioCheckType(rio *r);

src/server.h

@@ -2056,6 +2056,7 @@ struct valkeyServer {
         long long reploff;
         long long read_reploff;
         int dbid;
+        uint64_t close_asap : 1;
     } repl_provisional_primary;
     client *cached_primary;             /* Cached primary to be reused for PSYNC. */
     int repl_syncio_timeout;            /* Timeout for synchronous I/O calls */

src/valkey-check-rdb.c

@@ -37,7 +37,7 @@
 #include <sys/stat.h>
 
 void createSharedObjects(void);
-void rdbLoadProgressCallback(rio *r, const void *buf, size_t len);
+int rdbLoadProgressCallback(rio *r, const void *buf, size_t len);
 int rdbCheckMode = 0;
 
 struct {