Messages in this thread | | | Date | Wed, 7 Sep 2022 14:53:42 -0700 | From | Brian Norris <> | Subject | Re: [PATCH 2/2] tracefs: Only clobber mode/uid/gid on remount if asked |
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On Wed, Sep 07, 2022 at 05:48:13PM -0400, Steven Rostedt wrote: > On Wed, 7 Sep 2022 17:46:04 -0400 > Steven Rostedt <rostedt@goodmis.org> wrote: > > > > # Don't change /sys/kernel/tracing/ permissions on automount. > > > umount /sys/kernel/debug/tracing/ > > > > BTW, I noticed that the above doesn't do anything. That is, > > you cannot unmount tracefs from /sys/kernel/debug/tracing.
Actually, it does work, but it's hard to observe. See below.
> I just saw your new email. I guess that's just how you were triggering the > automount, by unmounting it. Right?
You trimmed the important line: stat /sys/kernel/debug/tracing/.
It's hard to observe directly that /sys/kernel/debug/tracing is unmounted, because traditional examination (stat(2), open(2), etc.) methods will re-trigger the automount. The automount is *supposed* to appear as if it is always there.
Try these:
umount /sys/kernel/debug/tracing/ grep tracefs /proc/mounts stat /sys/kernel/debug/tracing/. grep tracefs /proc/mounts
The first and the second grep will give you different results.
> A lot of assumptions about what people may know ;-)
Yes, I suppose. That's also why I figured I'd write a test case, because test cases tell you exactly what is meant.
Brian
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