From: Gabriel Totev Date: Wed, 16 Apr 2025 22:42:08 +0000 (-0400) Subject: apparmor: shift ouid when mediating hard links in userns X-Git-Tag: v6.16.2~144 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=b6fba5d79289c94716774ae4ef8c41cd701988ae;p=thirdparty%2Fkernel%2Fstable.git apparmor: shift ouid when mediating hard links in userns [ Upstream commit c5bf96d20fd787e4909b755de4705d52f3458836 ] When using AppArmor profiles inside an unprivileged container, the link operation observes an unshifted ouid. (tested with LXD and Incus) For example, root inside container and uid 1000000 outside, with `owner /root/link l,` profile entry for ln: /root$ touch chain && ln chain link ==> dmesg apparmor="DENIED" operation="link" class="file" namespace="root//lxd-feet_" profile="linkit" name="/root/link" pid=1655 comm="ln" requested_mask="l" denied_mask="l" fsuid=1000000 ouid=0 [<== should be 1000000] target="/root/chain" Fix by mapping inode uid of old_dentry in aa_path_link() rather than using it directly, similarly to how it's mapped in __file_path_perm() later in the file. Signed-off-by: Gabriel Totev Signed-off-by: John Johansen Signed-off-by: Sasha Levin --- diff --git a/security/apparmor/file.c b/security/apparmor/file.c index d52a5b14dad4c..62bc46e037588 100644 --- a/security/apparmor/file.c +++ b/security/apparmor/file.c @@ -423,9 +423,11 @@ int aa_path_link(const struct cred *subj_cred, { struct path link = { .mnt = new_dir->mnt, .dentry = new_dentry }; struct path target = { .mnt = new_dir->mnt, .dentry = old_dentry }; + struct inode *inode = d_backing_inode(old_dentry); + vfsuid_t vfsuid = i_uid_into_vfsuid(mnt_idmap(target.mnt), inode); struct path_cond cond = { - d_backing_inode(old_dentry)->i_uid, - d_backing_inode(old_dentry)->i_mode + .uid = vfsuid_into_kuid(vfsuid), + .mode = inode->i_mode, }; char *buffer = NULL, *buffer2 = NULL; struct aa_profile *profile;