exec'ing from a thread is an interesting problem; the semantics of exec
should be to terminal all the threads before the exec occurs according
to http://maxim.int.ru/bookshelf/PthreadsProgram/htm/r_44.html
The normal idiom would be to do:
fork()
child exec's
parent waits for child
I'm not sure in your case if you desire all the threads to terminate
after the exec, so the wait() may be in fact be replaced by pthread
termination calls on all the threads for your implementation.
Unfortunately there is an issue with fork'ing in a thread; any mutex
held by another thread at the moment of fork becomes locked forever
since we have once mutex locked by the parent and one by the child.
Normally one would therefore use pthread_atfork() to help workaround
this issue, see https://stackoverflow.com/questions/14407544/mixing-
threads-fork-and-mutexes-what-should-i-watch-out-for
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You received this bug notification because you are a member of Kernel
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https://bugs.launchpad.net/bugs/1672819
Title:
exec'ing a setuid binary from a threaded program sometimes fails to
setuid
Status in Linux:
Unknown
Status in linux package in Ubuntu:
Triaged
Status in linux source package in Xenial:
In Progress
Bug description:
This can be reproduced with
https://gist.github.com/chipaca/806c90d96c437444f27f45a83d00a813
With that, and go 1.8, if you run “make” and then
for i in `seq 99`; do ./a_go; done
you'll see a variable number of ”GOT 1000” (or whatever your user id
is). If you don't, add one or two more 9s on there.
That's a simple go reproducer. You can also use “a_p” instead of
“a_go” to see one that only uses pthreads. “a_c” is a C version that
does *not* reproduce the issue.
But it's not pthreads: if in a_go.go you comment out the “import "C"”,
you'll still see the “GOT 1000” messages, in a static binary that uses
no pthreads, just clone(2). You'll also see a bunch of warnings
because it's not properly handling an EAGAIN from clone, but that's
unrelated.
If you pin the process to a single thread using taskset, you don't get
the issue from a_go; a_p continues to reproduce the issue. In some
virtualized environments we haven't been able to reproduce the issue
either (e.g. some aws instances), but kvm works (you need -smp to see
the issue from a_go).
ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: linux-image-4.4.0-64-generic 4.4.0-64.85
ProcVersionSignature: Ubuntu 4.4.0-64.85-generic 4.4.44
Uname: Linux 4.4.0-64-generic x86_64
NonfreeKernelModules: zfs zunicode zcommon znvpair zavl
ApportVersion: 2.20.1-0ubuntu2.5
Architecture: amd64
AudioDevicesInUse:
USER PID ACCESS COMMAND
/dev/snd/pcmC0D0p: john 2354 F...m pulseaudio
/dev/snd/controlC0: john 2354 F.... pulseaudio
CurrentDesktop: Unity
Date: Tue Mar 14 17:17:23 2017
HibernationDevice: RESUME=UUID=b9fd155b-dcbe-4337-ae77-6daa6569beaf
InstallationDate: Installed on 2014-04-27 (1051 days ago)
InstallationMedia: Ubuntu 14.04 LTS "Trusty Tahr" - Release amd64 (20140417)
MachineType: Dell Inc. Latitude E6510
ProcFB: 0 inteldrmfb
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-4.4.0-64-generic
root=/dev/mapper/ubuntu--vg-root ro enable_mtrr_cleanup mtrr_spare_reg_nr=8
mtrr_gran_size=32M mtrr_chunk_size=32M quiet splash
RelatedPackageVersions:
linux-restricted-modules-4.4.0-64-generic N/A
linux-backports-modules-4.4.0-64-generic N/A
linux-firmware 1.157.8
SourcePackage: linux
SystemImageInfo: Error: command ['system-image-cli', '-i'] failed with exit
code 2:
UpgradeStatus: Upgraded to xenial on 2015-06-18 (634 days ago)
dmi.bios.date: 12/05/2013
dmi.bios.vendor: Dell Inc.
dmi.bios.version: A16
dmi.board.vendor: Dell Inc.
dmi.chassis.type: 9
dmi.chassis.vendor: Dell Inc.
dmi.modalias:
dmi:bvnDellInc.:bvrA16:bd12/05/2013:svnDellInc.:pnLatitudeE6510:pvr0001:rvnDellInc.:rn:rvr:cvnDellInc.:ct9:cvr:
dmi.product.name: Latitude E6510
dmi.product.version: 0001
dmi.sys.vendor: Dell Inc.
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