Public bug reported:
In Ubuntu 20.04 I'm having problem with accessing shared memory segments
by different users. The associated files are created using shm_open()
with the combination of O_CREAT and O_RDWR flags and placed in /dev/shm.
The example of such a code is in the enclosed source file.
When I run it for the first time, it works as expected and
/dev/shm/testshm is created:
$ ls -la /dev/shm
total 0
drwxrwxrwt 2 root root 60 Aug 3 16:34 .
drwxr-xr-x 18 root root 4580 Aug 3 12:41 ..
-rw-rw-r-- 1 krejci krejci 0 Aug 3 14:37 testshm
Then running program again under the same user works fine, but when I
try to run the program as root (or any other user), I'm getting
"Permission denied":
# id
uid=0(root) gid=0(root) groups=0(root)
# ./test
return value -1
result 13: Permission denied
The example program works as expected on previous Ubuntu (18.04, 19.10)
releases as well as on other linux distros - other users has access
according to the set permissions (root is always able to access it).
ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: libc6 2.31-0ubuntu9
ProcVersionSignature: Ubuntu 5.4.0-42.46-generic 5.4.44
Uname: Linux 5.4.0-42-generic x86_64
ApportVersion: 2.20.11-0ubuntu27.4
Architecture: amd64
CasperMD5CheckResult: skip
Date: Mon Aug 3 17:35:07 2020
InstallationDate: Installed on 2020-08-03 (0 days ago)
InstallationMedia: Ubuntu 20.04 LTS "Focal Fossa" - Release amd64 (20200423)
SourcePackage: glibc
UpgradeStatus: No upgrade log present (probably fresh install)
** Affects: ubuntu
Importance: Undecided
Status: New
** Tags: amd64 apport-bug focal
** Attachment added: "example application referenced in the issue description"
https://bugs.launchpad.net/bugs/1890168/+attachment/5398341/+files/test.c
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https://bugs.launchpad.net/bugs/1890168
Title:
shm_open() fails with EACCESS for root user
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