From: Laszlo Ersek <lersek@redhat.com>
To: Max Reitz <mreitz@redhat.com>,
"qemu-devel@nongnu.org" <qemu-devel@nongnu.org>
Cc: Kevin Wolf <kwolf@redhat.com>, Stefan Hajnoczi <stefanha@redhat.com>
Subject: Re: Thread safety of coroutine-sigaltstack
Date: Thu, 21 Jan 2021 17:05:17 +0100 [thread overview]
Message-ID: <47c2c4de-7f8e-e64b-452e-e7b0f3e9d48d@redhat.com> (raw)
In-Reply-To: <eb4fb436-e7d7-2f5c-c1a4-9f5e57804e54@redhat.com>
On 01/21/21 16:42, Max Reitz wrote:
> Perhaps we have the policy of “If another process can send signals, then
> we consider it to have full control over qemu, like a debugger.”
That's what I had more or less in mind, yes; see e.g.
https://man7.org/linux/man-pages/man2/ptrace.2.html
EPERM The specified process cannot be traced. This could be
because the tracer has insufficient privileges (the
required capability is CAP_SYS_PTRACE); unprivileged
processes cannot trace processes that they cannot send
signals to or those running set-user-ID/set-group-ID
programs, for obvious reasons. Alternatively, the process
may already be being traced, or (on kernels before 2.6.26)
be init(1) (PID 1).
Which seems to imply that, if you can send a signal, you can ptrace()
the signalee as well.
(I realize that what I'm saying does not follow from *pure logic*, as
the manual is stating !sendsig -> !trace, hence trace -> sendsig.
Whereas we're discussing the opposite direction: sendsig -> trace.
*But*, IMO, that direction is *suggested* by the manual.)
Anyway, this is kind of moot; I'm OK with the mutex too. :)
Thanks
Laszlo
next prev parent reply other threads:[~2021-01-21 16:08 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-20 16:26 Thread safety of coroutine-sigaltstack Max Reitz
2021-01-20 16:50 ` Paolo Bonzini
2021-01-20 16:58 ` Eric Blake
2021-01-20 17:25 ` Laszlo Ersek
2021-01-21 9:27 ` Max Reitz
2021-01-21 13:34 ` Laszlo Ersek
2021-01-21 15:42 ` Max Reitz
2021-01-21 16:04 ` Daniel P. Berrangé
2021-01-21 16:05 ` Laszlo Ersek [this message]
2021-01-21 15:14 ` Paolo Bonzini
2021-01-21 16:07 ` Daniel P. Berrangé
2021-01-21 16:44 ` Peter Maydell
2021-01-21 17:24 ` Paolo Bonzini
2021-01-22 20:38 ` Laszlo Ersek
2021-01-22 21:34 ` Laszlo Ersek
2021-01-22 21:41 ` Laszlo Ersek
2021-01-22 7:55 ` Markus Armbruster
2021-01-22 8:48 ` Max Reitz
2021-01-22 10:14 ` Peter Maydell
2021-01-22 10:16 ` Max Reitz
2021-01-22 12:24 ` Laszlo Ersek
2021-01-23 0:06 ` Laszlo Ersek
2021-01-23 13:35 ` Peter Maydell
2021-01-25 22:15 ` Laszlo Ersek
2021-01-25 22:45 ` Paolo Bonzini
2021-01-26 8:57 ` Laszlo Ersek
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