diff options
| -rw-r--r-- | fs/exec.c | 2 | ||||
| -rw-r--r-- | fs/namespace.c | 13 | ||||
| -rw-r--r-- | include/linux/mount.h | 1 | ||||
| -rw-r--r-- | security/commoncap.c | 8 | ||||
| -rw-r--r-- | security/selinux/hooks.c | 2 |
5 files changed, 23 insertions, 3 deletions
diff --git a/fs/exec.c b/fs/exec.c index 887c1c955df8..ca239fc86d8d 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -1411,7 +1411,7 @@ static void bprm_fill_uid(struct linux_binprm *bprm) bprm->cred->euid = current_euid(); bprm->cred->egid = current_egid(); - if (bprm->file->f_path.mnt->mnt_flags & MNT_NOSUID) + if (!mnt_may_suid(bprm->file->f_path.mnt)) return; if (task_no_new_privs(current)) diff --git a/fs/namespace.c b/fs/namespace.c index 9786a38d1681..aabe8e397fc3 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -3280,6 +3280,19 @@ static bool mount_too_revealing(struct vfsmount *mnt, int *new_mnt_flags) return !mnt_already_visible(ns, mnt, new_mnt_flags); } +bool mnt_may_suid(struct vfsmount *mnt) +{ + /* + * Foreign mounts (accessed via fchdir or through /proc + * symlinks) are always treated as if they are nosuid. This + * prevents namespaces from trusting potentially unsafe + * suid/sgid bits, file caps, or security labels that originate + * in other namespaces. + */ + return !(mnt->mnt_flags & MNT_NOSUID) && check_mnt(real_mount(mnt)) && + current_in_userns(mnt->mnt_sb->s_user_ns); +} + static struct ns_common *mntns_get(struct task_struct *task) { struct ns_common *ns = NULL; diff --git a/include/linux/mount.h b/include/linux/mount.h index f822c3c11377..54a594d49733 100644 --- a/include/linux/mount.h +++ b/include/linux/mount.h @@ -81,6 +81,7 @@ extern void mntput(struct vfsmount *mnt); extern struct vfsmount *mntget(struct vfsmount *mnt); extern struct vfsmount *mnt_clone_internal(struct path *path); extern int __mnt_is_readonly(struct vfsmount *mnt); +extern bool mnt_may_suid(struct vfsmount *mnt); struct path; extern struct vfsmount *clone_private_mount(struct path *path); diff --git a/security/commoncap.c b/security/commoncap.c index e109e6dac858..14540bd78561 100644 --- a/security/commoncap.c +++ b/security/commoncap.c @@ -453,8 +453,14 @@ static int get_file_caps(struct linux_binprm *bprm, bool *effective, bool *has_c if (!file_caps_enabled) return 0; - if (bprm->file->f_path.mnt->mnt_flags & MNT_NOSUID) + if (!mnt_may_suid(bprm->file->f_path.mnt)) return 0; + + /* + * This check is redundant with mnt_may_suid() but is kept to make + * explicit that capability bits are limited to s_user_ns and its + * descendants. + */ if (!current_in_userns(bprm->file->f_path.mnt->mnt_sb->s_user_ns)) return 0; diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c index a86d537eb79b..15541756eb07 100644 --- a/security/selinux/hooks.c +++ b/security/selinux/hooks.c @@ -2259,7 +2259,7 @@ static int check_nnp_nosuid(const struct linux_binprm *bprm, const struct task_security_struct *new_tsec) { int nnp = (bprm->unsafe & LSM_UNSAFE_NO_NEW_PRIVS); - int nosuid = (bprm->file->f_path.mnt->mnt_flags & MNT_NOSUID); + int nosuid = !mnt_may_suid(bprm->file->f_path.mnt); int rc; if (!nnp && !nosuid) |