From 01593d3299a1cfdb5e08acf95f63ec59dd674906 Mon Sep 17 00:00:00 2001 From: Stephen Smalley Date: Mon, 9 Jan 2017 10:07:31 -0500 Subject: [PATCH] selinux: allow context mounts on tmpfs, ramfs, devpts within user namespaces commit aad82892af261b9903cc11c55be3ecf5f0b0b4f8 ("selinux: Add support for unprivileged mounts from user namespaces") prohibited any use of context mount options within non-init user namespaces. However, this breaks use of context mount options for tmpfs mounts within user namespaces, which are being used by Docker/runc. There is no reason to block such usage for tmpfs, ramfs or devpts. Exempt these filesystem types from this restriction. Before: sh$ userns_child_exec -p -m -U -M '0 1000 1' -G '0 1000 1' bash sh# mount -t tmpfs -o context=system_u:object_r:user_tmp_t:s0:c13 none /tmp mount: tmpfs is write-protected, mounting read-only mount: cannot mount tmpfs read-only After: sh$ userns_child_exec -p -m -U -M '0 1000 1' -G '0 1000 1' bash sh# mount -t tmpfs -o context=system_u:object_r:user_tmp_t:s0:c13 none /tmp sh# ls -Zd /tmp unconfined_u:object_r:user_tmp_t:s0:c13 /tmp Signed-off-by: Stephen Smalley Signed-off-by: Paul Moore --- security/selinux/hooks.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c index e4b953f760dd..e32f4b5f23a5 100644 --- a/security/selinux/hooks.c +++ b/security/selinux/hooks.c @@ -834,10 +834,14 @@ static int selinux_set_mnt_opts(struct super_block *sb, } /* - * If this is a user namespace mount, no contexts are allowed - * on the command line and security labels must be ignored. + * If this is a user namespace mount and the filesystem type is not + * explicitly whitelisted, then no contexts are allowed on the command + * line and security labels must be ignored. */ - if (sb->s_user_ns != &init_user_ns) { + if (sb->s_user_ns != &init_user_ns && + strcmp(sb->s_type->name, "tmpfs") && + strcmp(sb->s_type->name, "ramfs") && + strcmp(sb->s_type->name, "devpts")) { if (context_sid || fscontext_sid || rootcontext_sid || defcontext_sid) { rc = -EACCES;