From 72ef56652d0a251bfa8e287d6b3a6cbb5b7eef90 Mon Sep 17 00:00:00 2001
From: Levi Neely <141506390+lneely@users.noreply.github.com>
Date: Tue, 3 Mar 2026 16:18:16 +0100
Subject: [PATCH] Fix race condition in pfs_reopen_file_for_writing encoder
 state (#329)

Crypto folder operations tested, no regression
---
 pclsync/pfs.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/pclsync/pfs.c b/pclsync/pfs.c
index 78af7ee..ecb8d6f 100644
--- a/pclsync/pfs.c
+++ b/pclsync/pfs.c
@@ -2130,17 +2130,24 @@ pfs_reopen_file_for_writing(psync_openfile_t *of) {
   if (unlikely(of->encrypted &&
                of->encoder == PSYNC_CRYPTO_UNLOADED_SECTOR_ENCODER)) {
     pcrypto_sector_encdec_t enc;
+    psync_fsfileid_t remotefileid;
+    uint64_t hash;
+    // Save values before unlock
+    remotefileid = of->remotefileid;
+    hash = of->hash;
     // we should unlock of->mutex as it can deadlock with sqllock and taking
     // sqllock before network operation is not a good idea
     pthread_mutex_unlock(&of->mutex);
-    enc = pcryptofolder_filencoder_get(of->remotefileid, of->hash, 0);
+    enc = pcryptofolder_filencoder_get(remotefileid, hash, 0);
     if (unlikely(psync_crypto_is_error(enc)))
       return -pfs_crypto_err_to_errno(psync_crypto_to_error(enc));
     pfs_lock_file(of);
-    if (of->encoder == PSYNC_CRYPTO_UNLOADED_SECTOR_ENCODER)
+    // Check if state changed while unlocked
+    if (of->encoder == PSYNC_CRYPTO_UNLOADED_SECTOR_ENCODER &&
+        of->remotefileid == remotefileid && of->hash == hash)
       of->encoder = enc;
     else
-      pcryptofolder_filencoder_release(of->remotefileid, of->hash, enc);
+      pcryptofolder_filencoder_release(remotefileid, hash, enc);
     if (of->newfile || of->modified)
       return 1;
   }