similar to: [nbdkit PATCH 0/3] sh plugin fixes

On Thu, Aug 01, 2019 at 10:42:58PM -0500, Eric Blake wrote: > setenv() is not async-signal-safe and as such should not be used > between fork/exec of a multi-threaded app: if one thread is > manipulating the current environment (which may entail obtaining a > malloc() mutex) when another thread calls fork(), the resulting > child's attempt to use setenv() could deadlock or see a

While nbdkit itself must run with SIGPIPE ignored, many applications expect to inherit SIGPIPE in the default state. What's worse, POSIX states that a non-interactive shell script cannot use 'trap' to undo an inherited SIG_IGN on SIGPIPE. I have seen several bug reports over the years of something that works for a developer but fails under a CI environment, where the root cause was

setenv() is not async-signal-safe and as such should not be used between fork/exec of a multi-threaded app: if one thread is manipulating the current environment (which may entail obtaining a malloc() mutex) when another thread calls fork(), the resulting child's attempt to use setenv() could deadlock or see a broken environ because the thread owning the lock no longer exists to release it.

This was a rather longer trip around the houses than I anticipated! The basic purpose of the patch series is to set $nbdkit_stdio_safe to "0" or "1" in sh and eval plugin scripts. To do that, I ended up adding a nicer way to manipulate environ lists, and to do that, I ended up adding a whole generic vector implementation which is applicable in a lot of different places.

If the user calls nbd_kill_subprocess, we shouldn't kill the process again when we close the handle (since the process has likely gone and we might be killing a different process). --- lib/handle.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/lib/handle.c b/lib/handle.c index 2af25fe..5ad818e 100644 --- a/lib/handle.c +++ b/lib/handle.c @@ -315,6 +315,8 @@

V3 was here: <http://mid.mail-archive.com/20230215141158.2426855-1-lersek at redhat.com>. See the Notes section on each patch for the v4 updates. The series is nearly ready for merging: every patch has at least one R-b tag, except "socket activation: avoid manipulating the sign bit". The series builds, and passes "make check" and "make check-valgrind", at

This is a major rewrite compared to my v1 series, where I've tried a lot harder to ensure that we still accommodate building on Haiku (although I have not actually yet fired up a Haiku VM to try it for myself). I also managed to make the sh plugin fully parallel, on capable platforms. See also my question on patch 10 on whether I've picked the best naming convention. Eric Blake (17):

Unfinished (needs tests). This is my attempt to make a "remote tmpfs" plugin as outlined in this prior email: https://www.redhat.com/archives/libguestfs/2020-March/msg00134.html Although it would be possible to construct something a bit like this using existing plugins and filters (perhaps with some new features in those filters) I think it may be nicer to have a dedicated plugin for

Needs some work still, see in particular the commit message for patch 3. Rich.

This can be used for creating temporary disks to thin clients, as a kind of "remote tmpfs". See also: https://www.redhat.com/archives/libguestfs/2020-March/msg00134.html --- plugins/data/nbdkit-data-plugin.pod | 1 + plugins/file/nbdkit-file-plugin.pod | 1 + plugins/linuxdisk/nbdkit-linuxdisk-plugin.pod | 7 +- plugins/memory/nbdkit-memory-plugin.pod |

On 8/31/23 10:02, Richard W.M. Jones wrote: > > On Wed, Aug 30, 2023 at 05:21:19PM -0500, Eric Blake wrote: >> I hit another transient failure in libnbd CI when a poorly-written >> eval script did not consume all of stdin during .pwrite. As behaving >> as a data sink can be a somewhat reasonable feature of a >> quickly-written sh or eval plugin, we should not be so

v2 was here: https://www.redhat.com/archives/libguestfs/2020-March/msg00154.html v3: - Micro-optimize tmpdir. - Quote $disk in default command shell fragment. - Don't redirect mkfs output to /dev/null. Instead use exec </dev/null >/dev/null before the shell fragment. We may want to do this in other places where we run external shell scripts, or more generally for all

Here's what I'm currently playing with; I'm not ready to commit anything until I rebase my FUA work on top of this, as I only want to break filter ABI once between releases. Eric Blake (2): backend: Rework internal/filter error return semantics filters: Add log filter TODO | 2 - docs/nbdkit-filter.pod | 84 +++++++-- docs/nbdkit.pod

v1 was posted here: https://www.redhat.com/archives/libguestfs/2019-September/thread.html#00337 v2: - Drop the first patch. - Hopefully fix the multiple issues with fork-safety and general behaviour on error paths. Note this requires execvpe for which there seems to be no equivalent on FreeBSD, except some kind of tedious path parsing (but can we assign to environ?) Rich.

I'm not someone who thinks VLAs are automatically bad and unlike Linux kernel code they can sometimes be used safely in userspace. However for an internet exposed server there is an argument that they might cause some kind of exploitable situation especially if the code is compiled without other stack hardening features. Also in highly multithreaded code with limited stack sizes (as nbdkit

The $tmpdir environment variable is used by the eval and sh plugins to communicate the path to the temporary directory created by the plugin for shell scripts to use for temporary files. Previously we set this environment variable globally (in .load()), but this means the environment variable can be leaked into undesirable places, eg. into the --run script: $ nbdkit sh - --run 'echo

?tempdir says By default, ?tmpdir? will be the directory given by ?tempdir()?. This will be a subdirectory of the temporary directory found by the following rule. The environment variables ?TMPDIR?, ?TMP? and ?TEMP? are checked in turn and the first found which points to a writable directory is used: if none succeeds ?/tmp? is used. Unfortunately, it doesn't seem to

This patch is against Cray patch against openssh-SNAP-20010710. Here a few notes about them: 1) rijndael does not work on cray due to the fact it is rooted in 32 bits. I looking for a fix, it may come form Wendy Palam. For now the cray default to the following cihpers for ssh version 2 ssh are: 3des-cbc,blowfish-cbc,cast128-cbc,arcfour 2) Crays don't have setitimer so I

Hi, One of the functions I use needs to write to a temporary file, in the directory given by tempdir(). I want to change this from the standard one, as the file is too large for the drive. However, tempfile() doesnt seem to respect the environment variables when I change them with Sys.setenv(). In a fresh R-session: > Sys.getenv("TMP") [1]

Since v1: add the blocksize filter, add testsuite coverage of the log filter, several fixes to the log filter based on what adding tests revealed I'm still working on FUA flag support patches on top of this; the patches should all be committed in the same release, as we want to minimize the number of releases that cause a filter ABI/API bump Eric Blake (3): backend: Rework internal/filter