On 16.08.21 21:44, Vivek Goyal wrote:
On Wed, Aug 11, 2021 at 08:41:18AM +0200, Hanna Reitz wrote:
[..]
But given the inotify complications, there’s really a good reason we should
use mountinfo.
It’s a bit tricky because our sandboxing prevents easy access to mountinfo,
but if that’s the only way...
yes. We already have lo->proc_self_fd. Maybe we need to keep
/proc/self/mountinfo open in lo->proc_self_mountinfo. I am assuming
that any mount table changes will still be visible despite the fact
I have fd open (and don't have to open new fd to notice new mount/unmount
changes).
Well, yes, that was my idea. Unfortunately, I wasn’t quite successful yet;
when I tried keeping the fd open, reading from it would just return 0
bytes. Perhaps that’s because we bind-mount /proc/self/fd to /proc so that
nothing else in /proc is visible. Perhaps we need to bind-mount
/proc/self/mountinfo into /proc/self/fd before that...
Or perhaps open /proc/self/mountinfo and save fd in lo->proc_mountinfo
before /proc/self/fd is bind mounted on /proc?
Yes, I tried that, and then reading would just return 0 bytes.
Hi Hanna,
I tried this simple patch and I can read /proc/self/mountinfo before
bind mounting /proc/self/fd and after bind mounting /proc/self/fd. Am
I missing something.
Yes, but I tried reading it in the main loop (where we’d actually need
it). It looks like the umount2(".", MNT_DETACH) in setup_mounts()
breaks it.
Hanna
