Let chown_common() lookup fsids in the fsid mappings. If no fsid mappings are setup the behavior is unchanged, i.e. fsids are looked up in the id mappings. do_faccessat() just needs to translate from real ids into fsids. Filesystems that share a superblock in all user namespaces they are mounted in will retain their old semantics even with the introduction of fsidmappings. Signed-off-by: Christian Brauner <christian.brauner@xxxxxxxxxx> --- /* v2 */ - Christian Brauner <christian.brauner@xxxxxxxxxx>: - handle faccessat() too --- fs/open.c | 16 ++++++++++++---- 1 file changed, 12 insertions(+), 4 deletions(-) diff --git a/fs/open.c b/fs/open.c index 0788b3715731..4e092845728f 100644 --- a/fs/open.c +++ b/fs/open.c @@ -32,6 +32,7 @@ #include <linux/ima.h> #include <linux/dnotify.h> #include <linux/compat.h> +#include <linux/fsuidgid.h> #include "internal.h" @@ -361,8 +362,10 @@ long do_faccessat(int dfd, const char __user *filename, int mode) if (!override_cred) return -ENOMEM; - override_cred->fsuid = override_cred->uid; - override_cred->fsgid = override_cred->gid; + override_cred->kfsuid = override_cred->uid; + override_cred->kfsgid = override_cred->gid; + override_cred->fsuid = kuid_to_kfsuid(override_cred->user_ns, override_cred->uid); + override_cred->fsgid = kgid_to_kfsgid(override_cred->user_ns, override_cred->gid); if (!issecure(SECURE_NO_SETUID_FIXUP)) { /* Clear the capabilities if we switch to a non-root user */ @@ -626,8 +629,13 @@ static int chown_common(const struct path *path, uid_t user, gid_t group) kuid_t uid; kgid_t gid; - uid = make_kuid(current_user_ns(), user); - gid = make_kgid(current_user_ns(), group); + if (is_userns_visible(inode->i_sb->s_iflags)) { + uid = make_kuid(current_user_ns(), user); + gid = make_kgid(current_user_ns(), group); + } else { + uid = make_kfsuid(current_user_ns(), user); + gid = make_kfsgid(current_user_ns(), group); + } retry_deleg: newattrs.ia_valid = ATTR_CTIME; -- 2.25.0