cifs: fix the race in cifs_writev()
O_APPEND handling there hadn't been completely fixed by Pavel's
patch; it checks the right value, but it's racy - we can't really
do that until i_mutex has been taken.
Fix by switching to __generic_file_aio_write() (open-coding
generic_file_aio_write(), actually) and pulling mutex_lock() above
inode_size_read().
Cc: stable@vger.kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index 3443b8f..5bac276 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -2579,19 +2579,32 @@
struct cifsInodeInfo *cinode = CIFS_I(inode);
struct TCP_Server_Info *server = tlink_tcon(cfile->tlink)->ses->server;
ssize_t rc = -EACCES;
- loff_t lock_pos = pos;
+ loff_t lock_pos = iocb->ki_pos;
- if (file->f_flags & O_APPEND)
- lock_pos = i_size_read(inode);
/*
* We need to hold the sem to be sure nobody modifies lock list
* with a brlock that prevents writing.
*/
down_read(&cinode->lock_sem);
+ mutex_lock(&inode->i_mutex);
+ if (file->f_flags & O_APPEND)
+ lock_pos = i_size_read(inode);
if (!cifs_find_lock_conflict(cfile, lock_pos, iov_length(iov, nr_segs),
server->vals->exclusive_lock_type, NULL,
- CIFS_WRITE_OP))
- rc = generic_file_aio_write(iocb, iov, nr_segs, pos);
+ CIFS_WRITE_OP)) {
+ rc = __generic_file_aio_write(iocb, iov, nr_segs);
+ mutex_unlock(&inode->i_mutex);
+
+ if (rc > 0) {
+ ssize_t err;
+
+ err = generic_write_sync(file, iocb->ki_pos - rc, rc);
+ if (rc < 0)
+ rc = err;
+ }
+ } else {
+ mutex_unlock(&inode->i_mutex);
+ }
up_read(&cinode->lock_sem);
return rc;
}