This is a note to let you know that I've just added the patch titled
fs/kernfs/dir: obey S_ISGID
to the 6.1-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
fs-kernfs-dir-obey-s_isgid.patch
and it can be found in the queue-6.1 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 202d5beb3cac5db88e5930c9c3b01e7f9b293caf
Author: Max Kellermann <max.kellermann@xxxxxxxxx>
Date: Fri Dec 8 10:33:10 2023 +0100
fs/kernfs/dir: obey S_ISGID
[ Upstream commit 5133bee62f0ea5d4c316d503cc0040cac5637601 ]
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@xxxxxxxxx>
Acked-by: Tejun Heo <tj@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20231208093310.297233-2-max.kellermann@xxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index 44842e6cf0a9..a00e11ebfa77 100644
--- a/fs/kernfs/dir.c
+++ b/fs/kernfs/dir.c
@@ -669,6 +669,18 @@ 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) {
