[pve-devel] [PATCH common/container 0/2] inherit attributes from preexisting directory during mountpoint setup

[pve-devel] [PATCH common/container 0/2] inherit attributes from preexisting directory during mountpoint setup

[Filip Schauer]

Make mount points inherit the uid, gid, and access mode if the directory
already exists in the container file system. This makes setting up mount
points more convenient when attributes different from uid=0, gid=0,
mode=755 are required.

As an example, this ensures that directories like /app/data and
/app/cache in the docker.io/weblate/weblate OCI image retain the correct
permissions when adding mount points over them.

While not explicitly specified by the OCI spec, this matches the
behaviour of implementations such as Docker and Podman.

Also add the fchmodat syscall, which is required to set the access mode
of a file descriptor that was obtained with open_tree.

pve-common:

Filip Schauer (1):
  tools: add fchmodat syscall

 src/PVE/Syscall.pm |  1 +
 src/PVE/Tools.pm   | 11 +++++++++++
 2 files changed, 12 insertions(+)


pve-container:

Filip Schauer (1):
  mountpoint_insert_staged: inherit attributes if directory already
    exists

 src/PVE/LXC.pm | 7 +++++++
 1 file changed, 7 insertions(+)


Summary over all repositories:
  3 files changed, 19 insertions(+), 0 deletions(-)

-- 
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[pve-devel] [PATCH common 1/2] tools: add fchmodat syscall

[Filip Schauer]

The fchmodat syscall changes the mode of a file relative to a file
descriptor.

Signed-off-by: Filip Schauer <f.schauer@proxmox.com>
---
 src/PVE/Syscall.pm |  1 +
 src/PVE/Tools.pm   | 11 +++++++++++
 2 files changed, 12 insertions(+)

diff --git a/src/PVE/Syscall.pm b/src/PVE/Syscall.pm
index 68e16fe..606cc56 100644
--- a/src/PVE/Syscall.pm
+++ b/src/PVE/Syscall.pm
@@ -22,6 +22,7 @@ BEGIN {
         setresuid => &SYS_setresuid,
         fallocate => &SYS_fallocate,
         fchownat => &SYS_fchownat,
+        fchmodat => &SYS_fchmodat,
         mount => &SYS_mount,
         renameat2 => &SYS_renameat2,
         open_tree => &SYS_open_tree,
diff --git a/src/PVE/Tools.pm b/src/PVE/Tools.pm
index 3c6f2fb..a7bb3da 100644
--- a/src/PVE/Tools.pm
+++ b/src/PVE/Tools.pm
@@ -1505,6 +1505,17 @@ sub fchownat($$$$$) {
     ) == 0;
 }
 
+sub fchmodat($$$$) {
+    my ($dirfd, $pathname, $mode, $flags) = @_;
+    return syscall(
+        PVE::Syscall::fchmodat,
+        int($dirfd),
+        $pathname,
+        int($mode),
+        int($flags),
+    ) == 0;
+}
+
 my $salt_starter = time();
 
 sub encrypt_pw {
-- 
2.47.3



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[pve-devel] [PATCH container 2/2] mountpoint_insert_staged: inherit attributes if directory already exists

[Filip Schauer]

Make mount points inherit the uid, gid, and access mode if the directory
already exists in the container file system. This makes setting up mount
points more convenient when attributes different from uid=0, gid=0,
mode=755 are required.

As an example, this ensures that directories like /app/data and
/app/cache in the docker.io/weblate/weblate OCI image retain the correct
permissions when adding mount points over them.

While not explicitly specified by the OCI spec, this matches the
behaviour of implementations such as Docker and Podman.

Signed-off-by: Filip Schauer <f.schauer@proxmox.com>
---
 src/PVE/LXC.pm | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/src/PVE/LXC.pm b/src/PVE/LXC.pm
index e5ff3a1..bf4899f 100644
--- a/src/PVE/LXC.pm
+++ b/src/PVE/LXC.pm
@@ -2130,6 +2130,13 @@ sub mountpoint_insert_staged {
 
     my $dest_fd = walk_tree_nofollow_fd('/', $rootdir_fd, $mp_dir, 1, $root_uid, $root_gid);
 
+    # Preserve attributes of destination directory
+    my ($mode, $uid, $gid) = (stat($dest_fd))[2, 4, 5];
+    PVE::Tools::fchownat(fileno($mount_fd), '', $uid, $gid, PVE::Tools::AT_EMPTY_PATH)
+        or die "failed to propagate uid and gid to mountpoint: $!\n";
+    PVE::Tools::fchmodat(fileno($mount_fd), '.', $mode, 0)
+        or die "failed to propagate access mode to mountpoint: $!\n";
+
     PVE::Tools::move_mount(
         fileno($mount_fd),
         '',
-- 
2.47.3



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Re: [pve-devel] [PATCH common/container 0/2] inherit attributes from preexisting directory during mountpoint setup

[Maximiliano Sandoval]

Filip Schauer <f.schauer@proxmox.com> writes:

> Make mount points inherit the uid, gid, and access mode if the directory
> already exists in the container file system. This makes setting up mount
> points more convenient when attributes different from uid=0, gid=0,
> mode=755 are required.
>
> As an example, this ensures that directories like /app/data and
> /app/cache in the docker.io/weblate/weblate OCI image retain the correct
> permissions when adding mount points over them.
>
> While not explicitly specified by the OCI spec, this matches the
> behaviour of implementations such as Docker and Podman.
>
> Also add the fchmodat syscall, which is required to set the access mode
> of a file descriptor that was obtained with open_tree.
>
> pve-common:
>
> Filip Schauer (1):
>   tools: add fchmodat syscall
>
>  src/PVE/Syscall.pm |  1 +
>  src/PVE/Tools.pm   | 11 +++++++++++
>  2 files changed, 12 insertions(+)
>
>
> pve-container:
>
> Filip Schauer (1):
>   mountpoint_insert_staged: inherit attributes if directory already
>     exists
>
>  src/PVE/LXC.pm | 7 +++++++
>  1 file changed, 7 insertions(+)
>
>
> Summary over all repositories:
>   3 files changed, 19 insertions(+), 0 deletions(-)

When used in conjunction with [1] this allows to run the weblate/weblate
image without errors. I also tested this with syncthing/syncthing and it
looks good.

[1] https://lore.proxmox.com/all/20251215174203.267293-1-f.schauer@proxmox.com/

Tested-by: Maximiliano Sandoval <m.sandoval@proxmox.com>

-- 
Maximiliano


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