From 3b7eb5e35d0f55541452e91ca66798c16a81ad4a Mon Sep 17 00:00:00 2001 From: Trond Myklebust Date: Wed, 24 Apr 2019 17:46:49 -0400 Subject: [PATCH] NFS: When mounting, don't share filesystems between different user namespaces If two different containers that share the same network namespace attempt to mount the same filesystem, we should not allow them to share the same super block if they do not share the same user namespace, since the user mappings on the wire will need to differ. Signed-off-by: Trond Myklebust Signed-off-by: Anna Schumaker --- fs/nfs/super.c | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/fs/nfs/super.c b/fs/nfs/super.c index 19783e8ba9fb..4f014c4c7bc1 100644 --- a/fs/nfs/super.c +++ b/fs/nfs/super.c @@ -2485,6 +2485,21 @@ static int nfs_compare_super_address(struct nfs_server *server1, return 1; } +static int nfs_compare_userns(const struct nfs_server *old, + const struct nfs_server *new) +{ + const struct user_namespace *oldns = &init_user_ns; + const struct user_namespace *newns = &init_user_ns; + + if (old->client && old->client->cl_cred) + oldns = old->client->cl_cred->user_ns; + if (new->client && new->client->cl_cred) + newns = new->client->cl_cred->user_ns; + if (oldns != newns) + return 0; + return 1; +} + static int nfs_compare_super(struct super_block *sb, void *data) { struct nfs_sb_mountdata *sb_mntdata = data; @@ -2498,6 +2513,8 @@ static int nfs_compare_super(struct super_block *sb, void *data) return 0; if (memcmp(&old->fsid, &server->fsid, sizeof(old->fsid)) != 0) return 0; + if (!nfs_compare_userns(old, server)) + return 0; return nfs_compare_mount_options(sb, server, mntflags); } -- 2.39.5