diff options
| -rw-r--r-- | security/selinux/hooks.c | 59 |
1 files changed, 47 insertions, 12 deletions
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c index b0e940497e23..6c90d491fab4 100644 --- a/security/selinux/hooks.c +++ b/security/selinux/hooks.c @@ -2097,6 +2097,41 @@ static int selinux_vm_enough_memory(struct mm_struct *mm, long pages) /* binprm security operations */ +static int check_nnp_nosuid(const struct linux_binprm *bprm, + const struct task_security_struct *old_tsec, + 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 rc; + + if (!nnp && !nosuid) + return 0; /* neither NNP nor nosuid */ + + if (new_tsec->sid == old_tsec->sid) + return 0; /* No change in credentials */ + + /* + * The only transitions we permit under NNP or nosuid + * are transitions to bounded SIDs, i.e. SIDs that are + * guaranteed to only be allowed a subset of the permissions + * of the current SID. + */ + rc = security_bounded_transition(old_tsec->sid, new_tsec->sid); + if (rc) { + /* + * On failure, preserve the errno values for NNP vs nosuid. + * NNP: Operation not permitted for caller. + * nosuid: Permission denied to file. + */ + if (nnp) + return -EPERM; + else + return -EACCES; + } + return 0; +} + static int selinux_bprm_set_creds(struct linux_binprm *bprm) { const struct task_security_struct *old_tsec; @@ -2133,14 +2168,10 @@ static int selinux_bprm_set_creds(struct linux_binprm *bprm) /* Reset exec SID on execve. */ new_tsec->exec_sid = 0; - /* - * Minimize confusion: if no_new_privs or nosuid and a - * transition is explicitly requested, then fail the exec. - */ - if (bprm->unsafe & LSM_UNSAFE_NO_NEW_PRIVS) - return -EPERM; - if (bprm->file->f_path.mnt->mnt_flags & MNT_NOSUID) - return -EACCES; + /* Fail on NNP or nosuid if not an allowed transition. */ + rc = check_nnp_nosuid(bprm, old_tsec, new_tsec); + if (rc) + return rc; } else { /* Check for a default transition on this program. */ rc = security_transition_sid(old_tsec->sid, isec->sid, @@ -2148,15 +2179,19 @@ static int selinux_bprm_set_creds(struct linux_binprm *bprm) &new_tsec->sid); if (rc) return rc; + + /* + * Fallback to old SID on NNP or nosuid if not an allowed + * transition. + */ + rc = check_nnp_nosuid(bprm, old_tsec, new_tsec); + if (rc) + new_tsec->sid = old_tsec->sid; } ad.type = LSM_AUDIT_DATA_PATH; ad.u.path = bprm->file->f_path; - if ((bprm->file->f_path.mnt->mnt_flags & MNT_NOSUID) || - (bprm->unsafe & LSM_UNSAFE_NO_NEW_PRIVS)) - new_tsec->sid = old_tsec->sid; - if (new_tsec->sid == old_tsec->sid) { rc = avc_has_perm(old_tsec->sid, isec->sid, SECCLASS_FILE, FILE__EXECUTE_NO_TRANS, &ad); |