Don't put restored process on foreground if we are background process #14
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AntonKozlov
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Aug 7, 2024
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| if (getppid() != tcgetpgrp(0)) { | ||
| pr_debug("Running in background, not setting foreground process"); | ||
| } else if (root_item->pgid == vpid(root_item)) { |
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This is not a simple change as it involves the state on checkpoint and the state on restore. So we are not restoring control group if restore runs in background.
- Is it possible that we now leave some states where we should still be foreground? E.g. restoring in subshell like
$ ( ( java -XX:CRaCRestoreFrom= ... ) )
(no &, but parent probably not a foreground?)
-
Can restoring in background negatively impact java process which may assume foreground?
-
If the job moved to foreground (`java -XX:CRaCRestoreFrom= ... & ; fg), does it work correctly?
pushkarnk
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to canonical/crac-criu
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May 28, 2025
Running the zdtm/static/unlink_regular00 test on Ubuntu 24.04 on aarch64
results in following error:
# ./zdtm.py run -t zdtm/static/unlink_regular00 -k always
userns is supported
=== Run 1/1 ================ zdtm/static/unlink_regular00
==================== Run zdtm/static/unlink_regular00 in ns ====================
Skipping rtc at root
Start test
Test is SUID
./unlink_regular00 --pidfile=unlink_regular00.pid --outfile=unlink_regular00.out --dirname=unlink_regular00.test
Run criu dump
*** buffer overflow detected ***: terminated
############# Test zdtm/static/unlink_regular00 FAIL at CRIU dump ##############
Test output: ================================
<<< ================================
Send the 9 signal to 47
Wait for zdtm/static/unlink_regular00(47) to die for 0.100000
##################################### FAIL #####################################
According to the backtrace:
#0 __pthread_kill_implementation (threadid=281473158467616, signo=signo@entry=6, no_tid=no_tid@entry=0) at ./nptl/pthread_kill.c:44
#1 0x0000ffff93477690 in __pthread_kill_internal (signo=6, threadid=<optimized out>) at ./nptl/pthread_kill.c:78
#2 0x0000ffff9342cb3c in __GI_raise (sig=sig@entry=6) at ../sysdeps/posix/raise.c:26
#3 0x0000ffff93417e00 in __GI_abort () at ./stdlib/abort.c:79
#4 0x0000ffff9346abf0 in __libc_message_impl (fmt=fmt@entry=0xffff93552a78 "*** %s ***: terminated\n") at ../sysdeps/posix/libc_fatal.c:132
#5 0x0000ffff934e81a8 in __GI___fortify_fail (msg=msg@entry=0xffff93552a28 "buffer overflow detected") at ./debug/fortify_fail.c:24
#6 0x0000ffff934e79e4 in __GI___chk_fail () at ./debug/chk_fail.c:28
#7 0x0000ffff934e9070 in ___snprintf_chk (s=s@entry=0xffffc6ed04a3 "testfile", maxlen=maxlen@entry=4056, flag=flag@entry=2, slen=slen@entry=4053,
format=format@entry=0xaaaacffe3888 "link_remap.%d") at ./debug/snprintf_chk.c:29
#8 0x0000aaaacff4b8b8 in snprintf (__fmt=0xaaaacffe3888 "link_remap.%d", __n=4056, __s=0xffffc6ed04a3 "testfile")
at /usr/include/aarch64-linux-gnu/bits/stdio2.h:54
#9 create_link_remap (path=path@entry=0xffffc6ed2901 "/zdtm/static/unlink_regular00.test/subdir/testfile", len=len@entry=60, lfd=lfd@entry=20,
idp=idp@entry=0xffffc6ed14ec, nsid=nsid@entry=0xaaaada2bac00, parms=parms@entry=0xffffc6ed2808, fallback=0xaaaacff4c6c0 <dump_linked_remap+96>,
fallback@entry=0xffffc6ed2797) at criu/files-reg.c:1164
CRaC#10 0x0000aaaacff4c6c0 in dump_linked_remap (path=path@entry=0xffffc6ed2901 "/zdtm/static/unlink_regular00.test/subdir/testfile", len=len@entry=60,
parms=parms@entry=0xffffc6ed2808, lfd=lfd@entry=20, id=id@entry=12, nsid=nsid@entry=0xaaaada2bac00, fallback=fallback@entry=0xffffc6ed2797)
at criu/files-reg.c:1198
CRaC#11 0x0000aaaacff4d8b0 in check_path_remap (nsid=0xaaaada2bac00, id=12, lfd=20, parms=0xffffc6ed2808, link=<optimized out>) at criu/files-reg.c:1426
CRaC#12 dump_one_reg_file (lfd=20, id=12, p=0xffffc6ed2808) at criu/files-reg.c:1827
CRaC#13 0x0000aaaacff51078 in dump_one_file (pid=<optimized out>, fd=4, lfd=20, opts=opts@entry=0xaaaada2ba2c0, ctl=ctl@entry=0xaaaada2c4d50,
e=e@entry=0xffffc6ed39c8, dfds=dfds@entry=0xaaaada2c3d40) at criu/files.c:581
CRaC#14 0x0000aaaacff5176c in dump_task_files_seized (ctl=ctl@entry=0xaaaada2c4d50, item=item@entry=0xaaaada2b8f80, dfds=dfds@entry=0xaaaada2c3d40)
at criu/files.c:657
CRaC#15 0x0000aaaacff3d3c0 in dump_one_task (parent_ie=0x0, item=0xaaaada2b8f80) at criu/cr-dump.c:1679
CRaC#16 cr_dump_tasks (pid=<optimized out>) at criu/cr-dump.c:2224
CRaC#17 0x0000aaaacff163a0 in main (argc=<optimized out>, argv=0xffffc6ed40e8, envp=<optimized out>) at criu/crtools.c:293
This line is the problem:
snprintf(tmp + 1, sizeof(link_name) - (size_t)(tmp - link_name - 1), "link_remap.%d", rfe.id);
The problem was that the `-1` was on the inside of the braces and not on
the outside. This way the destination size was increase by 1 instead of
being decreased by 1 which triggered the buffer overflow detection.
Signed-off-by: Adrian Reber <[email protected]>
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When the restore is executed in background (e.g. using
java -XX:CRaCRestoreFrom=... &) and the restored process receives foreground forcefully, when this exits the parent shell (not on foreground) tries to read input and receives EOF, subsequently exiting. For users this might look as if the bash terminal gets suddenly closed for no reason at all.