file locking: check return value of fcntl ()

docs/changes.txt

@@ -74,6 +74,7 @@
 - OpenCL Kernel: Renumbered hash-mode 7600 to 4521
 - OpenCL Device: Do a check on available constant memory size and abort if it's less than 64kB
 - File Reads: Improved error detection on file reads, especially when getting the file stats
+- File Locking: Improved error detection on file locks
 - Sessions: Move out handling of multiple instance from restore file into separate pidfile
 - Threads: Restored strerror as %m is unsupported by the BSDs
 - Wordlists: Disable dictstat handling for hash-mode 3000 as it virtually creates words in the wordlist which is not the case for other modes

include/locking.h

@@ -13,7 +13,7 @@
 #include <errno.h>
 #include <fcntl.h>
 
-int  lock_file   (FILE *fp);
-void unlock_file (FILE *fp);
+int lock_file   (FILE *fp);
+int unlock_file (FILE *fp);
 
 #endif // _LOCKING_H

src/locking.c

@@ -27,7 +27,7 @@ int lock_file (FILE *fp)
   return 0;
 }
 
-void unlock_file (FILE *fp)
+int unlock_file (FILE *fp)
 {
   struct flock lock;
 
@@ -35,7 +35,12 @@ void unlock_file (FILE *fp)
 
   lock.l_type = F_UNLCK;
 
-  fcntl (fileno (fp), F_SETLK, &lock);
+  if (fcntl (fileno (fp), F_SETLK, &lock))
+  {
+    return -1;
+  }
+
+  return 0;
 }
 
 #else
@@ -47,7 +52,7 @@ int lock_file (MAYBE_UNUSED FILE *fp)
   return 0;
 }
 
-void unlock_file (MAYBE_UNUSED FILE *fp)
+int unlock_file (MAYBE_UNUSED FILE *fp)
 {
   // we should put windows specific code here
 }

src/loopback.c

@@ -163,7 +163,10 @@ void loopback_write_append (hashcat_ctx_t *hashcat_ctx, const u8 *plain_ptr, con
 
   fflush (fp);
 
-  unlock_file (fp);
+  if (unlock_file (fp))
+  {
+    event_log_error (hashcat_ctx, "%s: Failed to unlock file", loopback_ctx->filename);
+  }
 
   loopback_ctx->unused = false;
 }

src/potfile.c

@@ -271,7 +271,10 @@ void potfile_write_append (hashcat_ctx_t *hashcat_ctx, const char *out_buf, u8 *
 
   fflush (potfile_ctx->fp);
 
-  unlock_file (potfile_ctx->fp);
+  if (unlock_file (potfile_ctx->fp))
+  {
+    event_log_error (hashcat_ctx, "%s: Failed to unlock file", potfile_ctx->filename);
+  }
 }
 
 void potfile_update_hash (hashcat_ctx_t *hashcat_ctx, hash_t *found, char *line_pw_buf, int line_pw_len)