Forgotten error handling in vfs_open.

[Tomas Brambora]

In vfs_ops.c, function vfs_open there are this two statements:

vfs_file_t *file = vfs_file_get(fd);
file->node = node;

However, vfs_file_get can return NULL, in which case file→node causes VFS to crash.

[Jakub Jermář]

This problem appears to be only theoretical, because fd is allocated by vfs_fd_alloc() and we know it is a good fd (from the previous test). Moreover, vfs_fd_alloc(), had a chance to call vfs_files_init(). Now that fd is valid, vfs_files_init() must have already succeeded and thus vfs_fd_get() cannot return NULL.

[Jakub Jermář]

In changeset:head,509, I added an assertion which checks file is not NULL. Seeing NULL in file would be totally unexpected in this context.