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Fix a hang when using git-annex with an old openssh 7.2p2

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Which had some weird inheriting of ssh FDs by sshd.

Bug was introduced in git-annex version 7.20200202.7.
This commit is contained in:
Joey Hess 2020-07-21 16:14:25 -04:00
parent b75aa68bfa
commit cb74cefde7
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GPG key ID: DB12DB0FF05F8F38
4 changed files with 61 additions and 7 deletions
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3
CHANGELOG
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@ -4,6 +4,9 @@ git-annex (8.20200720.2) UNRELEASED; urgency=medium
like git-annex add with -J. Bug was introduced as part of a different FD
leak fix in version 6.20160318.
* Support building with dlist-1.0
* Fix a hang when using git-annex with an old openssh 7.2p2, which had
some weird inheriting of ssh FDs by sshd. Bug was introduced in
git-annex version 7.20200202.7.
-- Joey Hess <id@joeyh.name> Tue, 21 Jul 2020 12:58:30 -0400

22
Git/Config.hs
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@ -22,6 +22,7 @@ import Git.Types
import qualified Git.Command
import qualified Git.Construct
import Utility.UserInfo
import Utility.ThreadScheduler
{- Returns a single git config setting, or a fallback value if not set. -}
get :: ConfigKey -> ConfigValue -> Repo -> ConfigValue
@ -214,13 +215,20 @@ fromPipe r cmd params st = tryNonAsync $ withCreateProcess p go
{ std_out = CreatePipe
, std_err = CreatePipe
}
go _ (Just hout) (Just herr) pid = do
(val, err) <- concurrently
(S.hGetContents hout)
(S.hGetContents herr)
forceSuccessProcess p pid
r' <- store val st r
return (r', val, err)
go _ (Just hout) (Just herr) pid =
withAsync (S.hGetContents herr) $ \errreader -> do
val <- S.hGetContents hout
-- In case the process exits while something else,
-- like a background process, keeps the stderr handle
-- open, don't block forever waiting for stderr.
-- A few seconds after finishing reading stdout
-- should get any error message.
err <- either id id <$>
wait errreader
`race` (threadDelaySeconds (Seconds 2) >> return mempty)
forceSuccessProcess p pid
r' <- store val st r
return (r', val, err)
go _ _ _ _ = error "internal"
{- Reads git config from a specified file and returns the repo populated

12
doc/bugs/Recent_hang_with_rsync_remote_with_older_systems___40__Xenial__44___Jessie__41__/comment_7_815bf1b8985a49a0fafbcddc7c96f9d6._comment Normal file
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@ -0,0 +1,12 @@
[[!comment format=mdwn
username="joey"
subject="""comment 7"""
date="2020-07-21T19:59:40Z"
content="""
Reproducer script did not work for me.
But in the meantime, 4c9ad1de4 has gotten into the built that script uses,
so whatever about that commit fixes or masks the problem, it seems.
(The other stall's reproducer script did still work.)
"""]]

31
doc/bugs/SSH-based_git-annex-init_hang_on_older_systems___40__Xenial__44___Jessie__41__/comment_4_c480f7fad76759742bbdc4837d8c0c36._comment Normal file
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@ -0,0 +1,31 @@
[[!comment format=mdwn
username="joey"
subject="""comment 4"""
date="2020-07-21T20:02:22Z"
content="""
Reproduced this with the script.
1798550 pts/0 S+ 0:00 | \_ /root/git-annex.linux/exe/git --library-path /root/git-annex.linux//lib:/root/git-annex.linux//usr/lib/x86_64-linux-gnu/gconv:/root/git-annex.linux//usr/lib/x86_64-linux-gnu/audit:/root/git-annex.linux//etc/ld.so.conf.d:/root/git-annex.linux//lib64:/root/git-annex.linux//lib/x86_64-linux-gnu:/root/git-annex.linux//usr/lib/x86_64-linux-gnu: /root/git-annex.linux/shimmed/git/git -C clone annex init --debug
1798579 pts/0 Sl+ 0:00 | \_ /root/git-annex.linux/exe/git-annex --library-path /root/git-annex.linux//lib:/root/git-annex.linux//usr/lib/x86_64-linux-gnu/gconv:/root/git-annex.linux//usr/lib/x86_64-linux-gnu/audit:/root/git-annex.linux//etc/ld.so.conf.d:/root/git-annex.linux//lib64:/root/git-annex.linux//lib/x86_64-linux-gnu:/root/git-annex.linux//usr/lib/x86_64-linux-gnu: /root/git-annex.linux/shimmed/git-annex/git-annex init --debug
1798596 pts/0 S+ 0:00 | \_ /root/git-annex.linux/exe/git --library-path /root/git-annex.linux//lib:/root/git-annex.linux//usr/lib/x86_64-linux-gnu/gconv:/root/git-annex.linux//usr/lib/x86_64-linux-gnu/audit:/root/git-annex.linux//etc/ld.so.conf.d:/root/git-annex.linux//lib64:/root/git-annex.linux//lib/x86_64-linux-gnu:/root/git-annex.linux//usr/lib/x86_64-linux-gnu: /root/git-annex.linux/shimmed/git/git --git-dir=.git --work-tree=. --literal-pathspecs cat-file --batch
1798597 pts/0 S+ 0:00 | \_ /root/git-annex.linux/exe/git --library-path /root/git-annex.linux//lib:/root/git-annex.linux//usr/lib/x86_64-linux-gnu/gconv:/root/git-annex.linux//usr/lib/x86_64-linux-gnu/audit:/root/git-annex.linux//etc/ld.so.conf.d:/root/git-annex.linux//lib64:/root/git-annex.linux//lib/x86_64-linux-gnu:/root/git-annex.linux//usr/lib/x86_64-linux-gnu: /root/git-annex.linux/shimmed/git/git --git-dir=.git --work-tree=. --literal-pathspecs cat-file --batch-check=%(objectname) %(objecttype) %(objectsize)
1798598 pts/0 S+ 0:00 | \_ /root/git-annex.linux/exe/git --library-path /root/git-annex.linux//lib:/root/git-annex.linux//usr/lib/x86_64-linux-gnu/gconv:/root/git-annex.linux//usr/lib/x86_64-linux-gnu/audit:/root/git-annex.linux//etc/ld.so.conf.d:/root/git-annex.linux//lib64:/root/git-annex.linux//lib/x86_64-linux-gnu:/root/git-annex.linux//usr/lib/x86_64-linux-gnu: /root/git-annex.linux/shimmed/git/git --git-dir=.git --work-tree=. --literal-pathspecs hash-object -w --stdin-paths --no-filters
1798628 pts/0 Z+ 0:00 | \_ [ssh] <defunct>
1798267 ? Ss 0:00 \_ /usr/sbin/sshd
1798629 ? Ss 0:00 | \_ sshd: root@notty
I killed 1798629 and git-annex stopped hanging. That seems to confirm my
theory that sshd has inherited the stderr handle that git-annex is waiting
for input on. That process had these FDs:
lrwx------ 1 root root 64 Jul 21 16:04 0 -> /dev/null
lrwx------ 1 root root 64 Jul 21 16:04 1 -> /dev/null
lrwx------ 1 root root 64 Jul 21 16:04 2 -> /dev/null
lrwx------ 1 root root 64 Jul 21 16:04 3 -> socket:[15959002]
lr-x------ 1 root root 64 Jul 21 16:04 4 -> pipe:[15956866]
l-wx------ 1 root root 64 Jul 21 16:04 5 -> pipe:[15956866]
So probably 4 or 5 was connected to git-annex on the other end.
I've applied my patch, to fix this one.
"""]]