Tracked down the cause to the Docker host, which runs on jammy, not
knowing about fchmodat2(). The syscall should normally return ENOTSUP
when called with AT_SYMLINK_NOFOLLOW on Linux, but the Docker seccomp
profile causes it to return EPERM, which confuses tar(1). Closing.
** Changed in: tar (Ubuntu)
Status: New => Invalid
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https://bugs.launchpad.net/bugs/2056302
Title:
tar(1) on noble gives EPERM [Operation not permitted] errors when
extracting symlinks
Status in tar package in Ubuntu:
Invalid
Bug description:
This concerns tar 1.35+dfsg-3 in Ubuntu noble. This does NOT affect
tar 1.34+dfsg-1.2ubuntu1.1 in mantic.
I'm seeing errors like this:
$ tar xvJf /extern/source/chromium_122.0.6261.111.orig.tar.xz --wildcards
chromium-122.0.6261.111/ash/webui/camera_app_ui/resources/cca\*
chromium-122.0.6261.111/ash/webui/camera_app_ui/resources/cca
tar: chromium-122.0.6261.111/ash/webui/camera_app_ui/resources/cca:
Cannot change mode to rwxr-xr-x: Operation not permitted
(I am running this in a noble Docker container environment, and the
command is extracting into normal user file space.)
This is what strace shows:
23 symlinkat("utils/cca.py", AT_FDCWD,
"chromium-122.0.6261.111/ash/webui/camera_app_ui/resources/cca") = 0
23 utimensat(AT_FDCWD,
"chromium-122.0.6261.111/ash/webui/camera_app_ui/resources/cca", [UTIME_OMIT,
{tv_sec=1709684076, tv_nsec=0} /* 2024-03-06T00:14:36+0000 */],
AT_SYMLINK_NOFOLLOW) = 0
23 newfstatat(AT_FDCWD,
"chromium-122.0.6261.111/ash/webui/camera_app_ui/resources/cca",
{st_mode=S_IFLNK|0777, st_size=12, ...}, AT_SYMLINK_NOFOLLOW) = 0
23 fchmodat2(AT_FDCWD,
"chromium-122.0.6261.111/ash/webui/camera_app_ui/resources/cca", 0755,
AT_SYMLINK_NOFOLLOW) = -1 EPERM (Operation not permitted)
The fchmodat(2) man page has the following verbiage:
AT_SYMLINK_NOFOLLOW
If pathname is a symbolic link, do not dereference it: instead
operate on the link itself. This flag is not currently imple‐
mented.
For comparison, this is what happens on mantic:
24 symlinkat("utils/cca.py", AT_FDCWD,
"chromium-122.0.6261.111/ash/webui/camera_app_ui/resources/cca") = 0
24 utimensat(AT_FDCWD,
"chromium-122.0.6261.111/ash/webui/camera_app_ui/resources/cca", [UTIME_OMIT,
{tv_sec=1709684076, tv_nsec=0} /* 2024-03-06T00:14:36+0000 */],
AT_SYMLINK_NOFOLLOW) = 0
24 newfstatat(AT_FDCWD,
"chromium-122.0.6261.111/ash/webui/camera_app_ui/resources/cca",
{st_mode=S_IFLNK|0777, st_size=12, ...}, AT_SYMLINK_NOFOLLOW) = 0
24 openat(AT_FDCWD,
"chromium-122.0.6261.111/ash/webui/camera_app_ui/resources/cca",
O_RDONLY|O_NOFOLLOW|O_CLOEXEC|O_PATH) = 3
24 newfstatat(3, "", {st_mode=S_IFLNK|0777, st_size=12, ...},
AT_EMPTY_PATH) = 0
24 close(3) = 0
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