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authorMax Kellermann <max.kellermann@ionos.com>2023-12-08 10:33:10 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2023-12-15 17:22:40 +0100
commit5133bee62f0ea5d4c316d503cc0040cac5637601 (patch)
tree88f212335c31aafcb840ace7ff61f179e39f79ad /fs/kernfs
parentkernel/cgroup: use kernfs_create_dir_ns() (diff)
downloadlinux-5133bee62f0ea5d4c316d503cc0040cac5637601.tar.xz
linux-5133bee62f0ea5d4c316d503cc0040cac5637601.zip
fs/kernfs/dir: obey S_ISGID
Handling of S_ISGID is usually done by inode_init_owner() in all other filesystems, but kernfs doesn't use that function. In kernfs, struct kernfs_node is the primary data structure, and struct inode is only created from it on demand. Therefore, inode_init_owner() can't be used and we need to imitate its behavior. S_ISGID support is useful for the cgroup filesystem; it allows subtrees managed by an unprivileged process to retain a certain owner gid, which then enables sharing access to the subtree with another unprivileged process. -- v1 -> v2: minor coding style fix (comment) Signed-off-by: Max Kellermann <max.kellermann@ionos.com> Acked-by: Tejun Heo <tj@kernel.org> Link: https://lore.kernel.org/r/20231208093310.297233-2-max.kellermann@ionos.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'fs/kernfs')
-rw-r--r--fs/kernfs/dir.c12
1 files changed, 12 insertions, 0 deletions
diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index 8b2bd65d70e7..62d39ecf0a46 100644
--- a/fs/kernfs/dir.c
+++ b/fs/kernfs/dir.c
@@ -676,6 +676,18 @@ struct kernfs_node *kernfs_new_node(struct kernfs_node *parent,
{
struct kernfs_node *kn;
+ if (parent->mode & S_ISGID) {
+ /* this code block imitates inode_init_owner() for
+ * kernfs
+ */
+
+ if (parent->iattr)
+ gid = parent->iattr->ia_gid;
+
+ if (flags & KERNFS_DIR)
+ mode |= S_ISGID;
+ }
+
kn = __kernfs_new_node(kernfs_root(parent), parent,
name, mode, uid, gid, flags);
if (kn) {