Fixes: #23520
[zjs: I added the comment and tweaked the patch a bit.
The call to reset_scheduled_shutdown() is moved down a bit to allow the
callback to have access to information about the operation being cancelled.
This all happens within the same function, so there should be no observable
change in behaviour.]
Fixes#23520. Replaces #23555.
The problem started with cdf370626f and
90b1ec03b2 which together started printing the
wall message in more cases. The motivation for those change was reasonable, but
this clearly causes problems described in #23520: users are getting unexpected
wall messages. Xterm, urxvt, (anything using libutempter?), and tmux (in some
configurations), register local pty sessions in utmp.
So let's try to suppress the message for local pseudo-terminal logins. This
patch based on #23538, but instead of filtering just on /dev/pts, it uses the
.ut_addr_v6 to only filter out local entries.
utmpdump doesn't print all the details. Looking at the list if useful
when trying to tweak the wall filtering logic.
This doesn't do much, but at least it serves as a smoke test for the cleanup
functions.
The casts in this and the next few commits are curently necessary
because CHAR8 is defined as uint8_t in gnu-efi, while char is signed.
Once we switch from gnu-efi typedefs to stdint types, the casts
will be dropped.
We currently have a convoluted and complex selection of which random
numbers to use. We can simplify this down to two functions that cover
all of our use cases:
1) Randomness for crypto: this one needs to wait until the RNG is
initialized. So it uses getrandom(0). If that's not available, it
polls on /dev/random, and then reads from /dev/urandom. This function
returns whether or not it was successful, as before.
2) Randomness for other things: this one uses getrandom(GRND_INSECURE).
If it's not available it uses getrandom(GRND_NONBLOCK). And if that
would block, then it falls back to /dev/urandom. And if /dev/urandom
isn't available, it uses the fallback code. It never fails and
doesn't return a value.
These two cases match all the uses of randomness inside of systemd.
I would prefer to make both of these return void, and get rid of the
fallback code, and simply assert in the incredibly unlikely case that
/dev/urandom doesn't exist. But Luca disagrees, so this commit attempts
to instead keep case (1) returning a return value, which all the callers
already check, and fix the fallback code in (2) to be less bad than
before.
For the less bad fallback code for (2), we now use auxval and some
timestamps, together with various counters representing the invocation,
hash it all together and provide the output. Provided that AT_RANDOM is
secure, this construction is probably okay too, though notably it
doesn't have any forward secrecy. Fortunately, it's only used by
random_bytes() and not by crypto_random_bytes().
After sending a SIGKILL to a process, the process might disappear from
`cgroup.threads` but still show up in `cgroup.procs` and still remains in the
cgroup and cause migrating new processes to `Delegate=yes` cgroups to fail with
`-EBUSY`. This is especially likely for heavyweight processes that consume more
kernel CPU time to clean up.
Fix this by only returning 0 when both `cgroup.threads` and
`cgroup.procs` are empty.
Zbigniew Jędrzejewski-Szmek
dependabot[bot]
Li kunyu
Christian Göttsche
Yu Watanabe
Alexander Shopov
Jan Janssen
Frantisek Sumsal
Matthias Lisin
Jason A. Donenfeld
msizanoen1