From: Al Viro Date: Thu, 3 Apr 2014 14:27:17 +0000 (-0400) Subject: cifs: fix the race in cifs_writev() X-Git-Tag: v3.15-rc1~16^2~1 X-Git-Url: http://git.agner.ch/gitweb/?p=linux.git;a=commitdiff_plain;h=19dfc1f5f2ef03a52aa30c8257c5745edef23f55 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 --- diff --git a/fs/cifs/file.c b/fs/cifs/file.c index 3443b8f8e1c0..5bac2763c450 100644 --- a/fs/cifs/file.c +++ b/fs/cifs/file.c @@ -2579,19 +2579,32 @@ cifs_writev(struct kiocb *iocb, const struct iovec *iov, 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; }