From 3cdf5b45ffbac294bcdfac0393df72f7687c01e8 Mon Sep 17 00:00:00 2001 From: "Eric W. Biederman" Date: Mon, 21 Nov 2011 16:40:54 -0800 Subject: [PATCH] userns: Ignore suid and sgid on binaries if the uid or gid can not be mapped When performing an exec where the binary lives in one user namespace and the execing process lives in another usre namespace there is the possibility that the target uids can not be represented. Instead of failing the exec simply ignore the suid/sgid bits and run the binary with lower privileges. We already do this in the case of MNT_NOSUID so this should be a well tested code path. As the user and group are not changed this should not introduce any security issues. Acked-by: Serge Hallyn Signed-off-by: Eric W. Biederman --- fs/exec.c | 9 +++------ 1 file changed, 3 insertions(+), 6 deletions(-) diff --git a/fs/exec.c b/fs/exec.c index 0039055b1fc6..aef0c2f19750 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -1266,14 +1266,13 @@ int prepare_binprm(struct linux_binprm *bprm) bprm->cred->egid = current_egid(); if (!(bprm->file->f_path.mnt->mnt_flags & MNT_NOSUID) && - !current->no_new_privs) { + !current->no_new_privs && + kuid_has_mapping(bprm->cred->user_ns, inode->i_uid) && + kgid_has_mapping(bprm->cred->user_ns, inode->i_gid)) { /* Set-uid? */ if (mode & S_ISUID) { - if (!kuid_has_mapping(bprm->cred->user_ns, inode->i_uid)) - return -EPERM; bprm->per_clear |= PER_CLEAR_ON_SETID; bprm->cred->euid = inode->i_uid; - } /* Set-gid? */ @@ -1283,8 +1282,6 @@ int prepare_binprm(struct linux_binprm *bprm) * executable. */ if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) { - if (!kgid_has_mapping(bprm->cred->user_ns, inode->i_gid)) - return -EPERM; bprm->per_clear |= PER_CLEAR_ON_SETID; bprm->cred->egid = inode->i_gid; } -- 2.20.1