Messages in this thread | | | Date | Thu, 12 Jul 2018 18:32:23 -0400 | From | "Theodore Y. Ts'o" <> | Subject | Re: [PATCH 24/32] vfs: syscall: Add fsopen() to prepare for superblock creation [ver #9] |
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On Thu, Jul 12, 2018 at 10:26:37PM +0100, David Howells wrote: > The problem is that there's more than one actual "open" involved. > > fd = fsopen("ext4"); <--- #1 > whatever_interface(fd, "s /dev/sda1"); > whatever_interface(fd, "o journal_path=/dev/sda2"); > do_the_create_thing(fd); <--- #2 and #3 > > The initial check to see whether you can mount or not is done at #1. > > But later there are two nested file opens. Internally, deep down inside the > block layer, /dev/sda1 and /dev/sda2 are opened and further permissions checks > are done, whether you like it or not. But these have no access to the creds > attached to fd as things currently stand.
So maybe the answer is that you open /dev/sda1 and /dev/sda2 and then pass the file descriptors to the fsopen object? We can require that the fd's be opened with O_RDWR and O_EXCL, which has the benefit where if you have multiple block devices, you know *which* block device had a problem with being grabbed for an exclusive open.
Just a thought.
- Ted
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