From f08b3f451f12eee4abd8a5981803bc36db84458b Mon Sep 17 00:00:00 2001 From: Namjae Jeon Date: Sat, 13 Jun 2026 22:00:00 +0900 Subject: [PATCH] ksmbd: use opener credentials for delete-on-close commit 52e2f21911158ec961cd5aae19c56460db382af0 upstream. Delete-on-close can be completed by deferred or durable handle teardown, where no request work is available. Both the base-file unlink and the ADS xattr removal consequently run with the ksmbd worker credentials and can bypass filesystem permission checks. Run both operations with the credentials captured in struct file when the handle was opened. This preserves the authenticated user's fsuid, fsgid, supplementary groups and capability restrictions at final close. Cc: stable@vger.kernel.org Reported-by: Musaab Khan Signed-off-by: Namjae Jeon Signed-off-by: Steve French Signed-off-by: Greg Kroah-Hartman --- fs/smb/server/vfs.c | 7 +++++-- fs/smb/server/vfs_cache.c | 4 ++++ 2 files changed, 9 insertions(+), 2 deletions(-) diff --git a/fs/smb/server/vfs.c b/fs/smb/server/vfs.c index 820352463a06..fb73e1be654d 100644 --- a/fs/smb/server/vfs.c +++ b/fs/smb/server/vfs.c @@ -1084,13 +1084,15 @@ int ksmbd_vfs_remove_xattr(struct mnt_idmap *idmap, int ksmbd_vfs_unlink(struct file *filp) { + const struct cred *saved_cred; int err = 0; struct dentry *dir, *dentry = filp->f_path.dentry; struct mnt_idmap *idmap = file_mnt_idmap(filp); + saved_cred = override_creds(filp->f_cred); err = mnt_want_write(filp->f_path.mnt); if (err) - return err; + goto out_revert; dir = dget_parent(dentry); err = ksmbd_vfs_lock_parent(dir, dentry); @@ -1110,7 +1112,8 @@ int ksmbd_vfs_unlink(struct file *filp) out: dput(dir); mnt_drop_write(filp->f_path.mnt); - +out_revert: + revert_creds(saved_cred); return err; } diff --git a/fs/smb/server/vfs_cache.c b/fs/smb/server/vfs_cache.c index 56335c4e4504..52d1432e2952 100644 --- a/fs/smb/server/vfs_cache.c +++ b/fs/smb/server/vfs_cache.c @@ -292,10 +292,14 @@ static void __ksmbd_inode_close(struct ksmbd_file *fp) up_write(&ci->m_lock); if (remove_stream_xattr) { + const struct cred *saved_cred; + + saved_cred = override_creds(filp->f_cred); err = ksmbd_vfs_remove_xattr(file_mnt_idmap(filp), &filp->f_path, fp->stream.name, true); + revert_creds(saved_cred); if (err) pr_err("remove xattr failed : %s\n", fp->stream.name);