From b4ff6ddb32296f43439b4be79c7864f7ae7d14f1 Mon Sep 17 00:00:00 2001
From: Ondrej Holy <oholy@redhat.com>
Date: Wed, 13 Nov 2024 11:34:19 +0100
Subject: [PATCH] smb: Fix offset after truncate when appending

The truncate operation is currently enabled when appending. However,
the libsmbclient doesn't support O_APPEND flag property [1]. The
offset is not reset after the truncate operation. This may lead to
data corruptions. Let's explicitely seek to the desired offset when
truncating to prevent this.

[1] https://github.com/samba-team/samba/blob/e4e3f05/source3/libsmb/libsmb_file.c#L162-L183
---
 daemon/gvfsbackendsmb.c | 27 ++++++++++++++++++++++++---
 1 file changed, 24 insertions(+), 3 deletions(-)

diff --git a/daemon/gvfsbackendsmb.c b/daemon/gvfsbackendsmb.c
index c2075555..f287264b 100644
--- a/daemon/gvfsbackendsmb.c
+++ b/daemon/gvfsbackendsmb.c
@@ -780,6 +780,7 @@ typedef struct {
   char *uri;
   char *tmp_uri;
   char *backup_uri;
+  GVfsJobOpenForWriteMode mode;
 } SmbWriteHandle;
 
 static void
@@ -824,6 +825,7 @@ do_create (GVfsBackend *backend,
     {
       handle = g_new0 (SmbWriteHandle, 1);
       handle->file = file;
+      handle->mode = job->mode;
 
       g_vfs_job_open_for_write_set_can_seek (job, TRUE);
       g_vfs_job_open_for_write_set_can_truncate (job, TRUE);
@@ -869,6 +871,7 @@ do_append_to (GVfsBackend *backend,
 
       handle = g_new0 (SmbWriteHandle, 1);
       handle->file = file;
+      handle->mode = job->mode;
 
       g_vfs_job_open_for_write_set_initial_offset (job, initial_offset);
 
@@ -1141,6 +1144,7 @@ do_replace (GVfsBackend *backend,
   handle->uri = uri;
   handle->tmp_uri = tmp_uri;
   handle->backup_uri = backup_uri;
+  handle->mode = job->mode;
   
   g_vfs_job_open_for_write_set_can_seek (job, TRUE);
   g_vfs_job_open_for_write_set_can_truncate (job, TRUE);
@@ -1229,9 +1233,26 @@ do_truncate (GVfsBackend *backend,
 
   smbc_ftruncate = smbc_getFunctionFtruncate (op_backend->smb_context);
   if (smbc_ftruncate (op_backend->smb_context, handle->file, size) == -1)
-    g_vfs_job_failed_from_errno (G_VFS_JOB (job), errno);
-  else
-    g_vfs_job_succeeded (G_VFS_JOB (job));
+    {
+      g_vfs_job_failed_from_errno (G_VFS_JOB (job), errno);
+      return;
+    }
+
+  if (handle->mode == OPEN_FOR_WRITE_APPEND)
+    {
+      smbc_lseek_fn smbc_lseek;
+      off_t res;
+
+      smbc_lseek = smbc_getFunctionLseek (op_backend->smb_context);
+      res = smbc_lseek (op_backend->smb_context, handle->file, size, SEEK_SET);
+      if (res == (off_t)-1)
+        {
+          g_vfs_job_failed_from_errno (G_VFS_JOB (job), errno);
+          return;
+        }
+    }
+
+  g_vfs_job_succeeded (G_VFS_JOB (job));
 }
 
 static void
-- 
2.46.2