Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace

Pull namespace updates from Eric Biederman:
 "After a lot of discussion and work we have finally reachanged a basic
  understanding of what is necessary to make unprivileged mounts safe in
  the presence of EVM and IMA xattrs which the last commit in this
  series reflects. While technically it is a revert the comments it adds
  are important for people not getting confused in the future. Clearing
  up that confusion allows us to seriously work on unprivileged mounts
  of fuse in the next development cycle.

  The rest of the fixes in this set are in the intersection of user
  namespaces, ptrace, and exec. I started with the first fix which
  started a feedback cycle of finding additional issues during review
  and fixing them. Culiminating in a fix for a bug that has been present
  since at least Linux v1.0.

  Potentially these fixes were candidates for being merged during the rc
  cycle, and are certainly backport candidates but enough little things
  turned up during review and testing that I decided they should be
  handled as part of the normal development process just to be certain
  there were not any great surprises when it came time to backport some
  of these fixes"

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace:
  Revert "evm: Translate user/group ids relative to s_user_ns when computing HMAC"
  exec: Ensure mm->user_ns contains the execed files
  ptrace: Don't allow accessing an undumpable mm
  ptrace: Capture the ptracer's creds not PT_PTRACE_CAP
  mm: Add a user_ns owner to mm_struct and fix ptrace permission checks

19 files changed, 139 insertions, 43 deletions

diff --git a/arch/alpha/kernel/ptrace.c b/arch/alpha/kernel/ptrace.c
index 940dfb406591..04abdec7f496 100644
--- a/arch/alpha/kernel/ptrace.c
+++ b/arch/alpha/kernel/ptrace.c
@@ -283,7 +283,7 @@ long arch_ptrace(struct task_struct *child, long request,
 	/* When I and D space are separate, these will need to be fixed.  */
 	case PTRACE_PEEKTEXT: /* read word at location addr. */
 	case PTRACE_PEEKDATA:
-		copied = access_process_vm(child, addr, &tmp, sizeof(tmp),
+		copied = ptrace_access_vm(child, addr, &tmp, sizeof(tmp),
 				FOLL_FORCE);
 		ret = -EIO;
 		if (copied != sizeof(tmp))
diff --git a/arch/blackfin/kernel/ptrace.c b/arch/blackfin/kernel/ptrace.c
index 8d79286ee4e8..360d99645163 100644
--- a/arch/blackfin/kernel/ptrace.c
+++ b/arch/blackfin/kernel/ptrace.c
@@ -270,7 +270,7 @@ long arch_ptrace(struct task_struct *child, long request,
 			switch (bfin_mem_access_type(addr, to_copy)) {
 			case BFIN_MEM_ACCESS_CORE:
 			case BFIN_MEM_ACCESS_CORE_ONLY:
-				copied = access_process_vm(child, addr, &tmp,
+				copied = ptrace_access_vm(child, addr, &tmp,
 							   to_copy, FOLL_FORCE);
 				if (copied)
 					break;
@@ -323,7 +323,7 @@ long arch_ptrace(struct task_struct *child, long request,
 			switch (bfin_mem_access_type(addr, to_copy)) {
 			case BFIN_MEM_ACCESS_CORE:
 			case BFIN_MEM_ACCESS_CORE_ONLY:
-				copied = access_process_vm(child, addr, &data,
+				copied = ptrace_access_vm(child, addr, &data,
 				                           to_copy,
 							   FOLL_FORCE | FOLL_WRITE);
 				break;
diff --git a/arch/cris/arch-v32/kernel/ptrace.c b/arch/cris/arch-v32/kernel/ptrace.c
index f0df654ac6fc..fe1f9cf7b391 100644
--- a/arch/cris/arch-v32/kernel/ptrace.c
+++ b/arch/cris/arch-v32/kernel/ptrace.c
@@ -147,7 +147,7 @@ long arch_ptrace(struct task_struct *child, long request,
 				/* The trampoline page is globally mapped, no page table to traverse.*/
 				tmp = *(unsigned long*)addr;
 			} else {
-				copied = access_process_vm(child, addr, &tmp, sizeof(tmp), FOLL_FORCE);
+				copied = ptrace_access_vm(child, addr, &tmp, sizeof(tmp), FOLL_FORCE);
 
 				if (copied != sizeof(tmp))
 					break;
diff --git a/arch/ia64/kernel/ptrace.c b/arch/ia64/kernel/ptrace.c
index 31aa8c0f68e1..36f660da8124 100644
--- a/arch/ia64/kernel/ptrace.c
+++ b/arch/ia64/kernel/ptrace.c
@@ -1159,7 +1159,7 @@ arch_ptrace (struct task_struct *child, long request,
 	case PTRACE_PEEKTEXT:
 	case PTRACE_PEEKDATA:
 		/* read word at location addr */
-		if (access_process_vm(child, addr, &data, sizeof(data),
+		if (ptrace_access_vm(child, addr, &data, sizeof(data),
 				FOLL_FORCE)
 		    != sizeof(data))
 			return -EIO;
diff --git a/arch/mips/kernel/ptrace32.c b/arch/mips/kernel/ptrace32.c
index 7e71a4e0281b..5fcbdcd7abd0 100644
--- a/arch/mips/kernel/ptrace32.c
+++ b/arch/mips/kernel/ptrace32.c
@@ -69,7 +69,7 @@ long compat_arch_ptrace(struct task_struct *child, compat_long_t request,
 		if (get_user(addrOthers, (u32 __user * __user *) (unsigned long) addr) != 0)
 			break;
 
-		copied = access_process_vm(child, (u64)addrOthers, &tmp,
+		copied = ptrace_access_vm(child, (u64)addrOthers, &tmp,
 				sizeof(tmp), FOLL_FORCE);
 		if (copied != sizeof(tmp))
 			break;
@@ -178,7 +178,7 @@ long compat_arch_ptrace(struct task_struct *child, compat_long_t request,
 		if (get_user(addrOthers, (u32 __user * __user *) (unsigned long) addr) != 0)
 			break;
 		ret = 0;
-		if (access_process_vm(child, (u64)addrOthers, &data,
+		if (ptrace_access_vm(child, (u64)addrOthers, &data,
 					sizeof(data),
 					FOLL_FORCE | FOLL_WRITE) == sizeof(data))
 			break;
diff --git a/arch/powerpc/kernel/ptrace32.c b/arch/powerpc/kernel/ptrace32.c
index 010b7b310237..1e887f3a61a6 100644
--- a/arch/powerpc/kernel/ptrace32.c
+++ b/arch/powerpc/kernel/ptrace32.c
@@ -73,7 +73,7 @@ long compat_arch_ptrace(struct task_struct *child, compat_long_t request,
 		if (get_user(addrOthers, (u32 __user * __user *)addr) != 0)
 			break;
 
-		copied = access_process_vm(child, (u64)addrOthers, &tmp,
+		copied = ptrace_access_vm(child, (u64)addrOthers, &tmp,
 				sizeof(tmp), FOLL_FORCE);
 		if (copied != sizeof(tmp))
 			break;
@@ -178,7 +178,7 @@ long compat_arch_ptrace(struct task_struct *child, compat_long_t request,
 		if (get_user(addrOthers, (u32 __user * __user *)addr) != 0)
 			break;
 		ret = 0;
-		if (access_process_vm(child, (u64)addrOthers, &tmp,
+		if (ptrace_access_vm(child, (u64)addrOthers, &tmp,
 					sizeof(tmp),
 					FOLL_FORCE | FOLL_WRITE) == sizeof(tmp))
 			break;
diff --git a/fs/exec.c b/fs/exec.c
index 923c57d96899..88b5e1efdbd6 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1277,8 +1277,22 @@ EXPORT_SYMBOL(flush_old_exec);
 
 void would_dump(struct linux_binprm *bprm, struct file *file)
 {
-	if (inode_permission(file_inode(file), MAY_READ) < 0)
+	struct inode *inode = file_inode(file);
+	if (inode_permission(inode, MAY_READ) < 0) {
+		struct user_namespace *old, *user_ns;
 		bprm->interp_flags |= BINPRM_FLAGS_ENFORCE_NONDUMP;
+
+		/* Ensure mm->user_ns contains the executable */
+		user_ns = old = bprm->mm->user_ns;
+		while ((user_ns != &init_user_ns) &&
+		       !privileged_wrt_inode_uidgid(user_ns, inode))
+			user_ns = user_ns->parent;
+
+		if (old != user_ns) {
+			bprm->mm->user_ns = get_user_ns(user_ns);
+			put_user_ns(old);
+		}
+	}
 }
 EXPORT_SYMBOL(would_dump);
 
@@ -1308,7 +1322,6 @@ void setup_new_exec(struct linux_binprm * bprm)
 	    !gid_eq(bprm->cred->gid, current_egid())) {
 		current->pdeath_signal = 0;
 	} else {
-		would_dump(bprm, bprm->file);
 		if (bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP)
 			set_dumpable(current->mm, suid_dumpable);
 	}
@@ -1408,7 +1421,7 @@ static void check_unsafe_exec(struct linux_binprm *bprm)
 	unsigned n_fs;
 
 	if (p->ptrace) {
-		if (p->ptrace & PT_PTRACE_CAP)
+		if (ptracer_capable(p, current_user_ns()))
 			bprm->unsafe |= LSM_UNSAFE_PTRACE_CAP;
 		else
 			bprm->unsafe |= LSM_UNSAFE_PTRACE;
@@ -1743,6 +1756,8 @@ static int do_execveat_common(int fd, struct filename *filename,
 	if (retval < 0)
 		goto out;
 
+	would_dump(bprm, bprm->file);
+
 	retval = exec_binprm(bprm);
 	if (retval < 0)
 		goto out;
diff --git a/include/linux/capability.h b/include/linux/capability.h
index dbc21c719ce6..6ffb67e10c06 100644
--- a/include/linux/capability.h
+++ b/include/linux/capability.h
@@ -240,8 +240,10 @@ static inline bool ns_capable_noaudit(struct user_namespace *ns, int cap)
 	return true;
 }
 #endif /* CONFIG_MULTIUSER */
+extern bool privileged_wrt_inode_uidgid(struct user_namespace *ns, const struct inode *inode);
 extern bool capable_wrt_inode_uidgid(const struct inode *inode, int cap);
 extern bool file_ns_capable(const struct file *file, struct user_namespace *ns, int cap);
+extern bool ptracer_capable(struct task_struct *tsk, struct user_namespace *ns);
 
 /* audit system wants to get cap info from files as well */
 extern int get_vfs_caps_from_disk(const struct dentry *dentry, struct cpu_vfs_cap_data *cpu_caps);
diff --git a/include/linux/mm.h b/include/linux/mm.h
index a92c8d73aeaf..0b5b2e4df14e 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1270,6 +1270,8 @@ extern int access_process_vm(struct task_struct *tsk, unsigned long addr, void *
 		unsigned int gup_flags);
 extern int access_remote_vm(struct mm_struct *mm, unsigned long addr,
 		void *buf, int len, unsigned int gup_flags);
+extern int __access_remote_vm(struct task_struct *tsk, struct mm_struct *mm,
+		unsigned long addr, void *buf, int len, unsigned int gup_flags);
 
 long get_user_pages_remote(struct task_struct *tsk, struct mm_struct *mm,
 			    unsigned long start, unsigned long nr_pages,
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 4a8acedf4b7d..08d947fc4c59 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -473,6 +473,7 @@ struct mm_struct {
 	 */
 	struct task_struct __rcu *owner;
 #endif
+	struct user_namespace *user_ns;
 
 	/* store ref to file /proc/<pid>/exe symlink points to */
 	struct file __rcu *exe_file;
diff --git a/include/linux/ptrace.h b/include/linux/ptrace.h
index 504c98a278d4..e0e539321ab9 100644
--- a/include/linux/ptrace.h
+++ b/include/linux/ptrace.h
@@ -8,6 +8,9 @@
 #include <linux/pid_namespace.h>	/* For task_active_pid_ns.  */
 #include <uapi/linux/ptrace.h>
 
+extern int ptrace_access_vm(struct task_struct *tsk, unsigned long addr,
+			    void *buf, int len, unsigned int gup_flags);
+
 /*
  * Ptrace flags
  *
@@ -19,7 +22,6 @@
 #define PT_SEIZED	0x00010000	/* SEIZE used, enable new behavior */
 #define PT_PTRACED	0x00000001
 #define PT_DTRACE	0x00000002	/* delayed trace (used on m68k, i386) */
-#define PT_PTRACE_CAP	0x00000004	/* ptracer can follow suid-exec */
 
 #define PT_OPT_FLAG_SHIFT	3
 /* PT_TRACE_* event enable flags */
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 5ccbbfe41345..a440cf178191 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1685,6 +1685,7 @@ struct task_struct {
 	struct list_head cpu_timers[3];
 
 /* process credentials */
+	const struct cred __rcu *ptracer_cred; /* Tracer's credentials at attach */
 	const struct cred __rcu *real_cred; /* objective and real subjective task
 					 * credentials (COW) */
 	const struct cred __rcu *cred;	/* effective (overridable) subjective task
diff --git a/kernel/capability.c b/kernel/capability.c
index 00411c82dac5..4984e1f552eb 100644
--- a/kernel/capability.c
+++ b/kernel/capability.c
@@ -457,6 +457,19 @@ bool file_ns_capable(const struct file *file, struct user_namespace *ns,
 EXPORT_SYMBOL(file_ns_capable);
 
 /**
+ * privileged_wrt_inode_uidgid - Do capabilities in the namespace work over the inode?
+ * @ns: The user namespace in question
+ * @inode: The inode in question
+ *
+ * Return true if the inode uid and gid are within the namespace.
+ */
+bool privileged_wrt_inode_uidgid(struct user_namespace *ns, const struct inode *inode)
+{
+	return kuid_has_mapping(ns, inode->i_uid) &&
+		kgid_has_mapping(ns, inode->i_gid);
+}
+
+/**
  * capable_wrt_inode_uidgid - Check nsown_capable and uid and gid mapped
  * @inode: The inode in question
  * @cap: The capability in question
@@ -469,7 +482,26 @@ bool capable_wrt_inode_uidgid(const struct inode *inode, int cap)
 {
 	struct user_namespace *ns = current_user_ns();
 
-	return ns_capable(ns, cap) && kuid_has_mapping(ns, inode->i_uid) &&
-		kgid_has_mapping(ns, inode->i_gid);
+	return ns_capable(ns, cap) && privileged_wrt_inode_uidgid(ns, inode);
 }
 EXPORT_SYMBOL(capable_wrt_inode_uidgid);
+
+/**
+ * ptracer_capable - Determine if the ptracer holds CAP_SYS_PTRACE in the namespace
+ * @tsk: The task that may be ptraced
+ * @ns: The user namespace to search for CAP_SYS_PTRACE in
+ *
+ * Return true if the task that is ptracing the current task had CAP_SYS_PTRACE
+ * in the specified user namespace.
+ */
+bool ptracer_capable(struct task_struct *tsk, struct user_namespace *ns)
+{
+	int ret = 0;  /* An absent tracer adds no restrictions */
+	const struct cred *cred;
+	rcu_read_lock();
+	cred = rcu_dereference(tsk->ptracer_cred);
+	if (cred)
+		ret = security_capable_noaudit(cred, ns, CAP_SYS_PTRACE);
+	rcu_read_unlock();
+	return (ret == 0);
+}
diff --git a/kernel/fork.c b/kernel/fork.c
index a439ac429669..869b8ccc00bf 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -747,7 +747,8 @@ static void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
 #endif
 }
 
-static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p)
+static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p,
+	struct user_namespace *user_ns)
 {
 	mm->mmap = NULL;
 	mm->mm_rb = RB_ROOT;
@@ -787,6 +788,7 @@ static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p)
 	if (init_new_context(p, mm))
 		goto fail_nocontext;
 
+	mm->user_ns = get_user_ns(user_ns);
 	return mm;
 
 fail_nocontext:
@@ -832,7 +834,7 @@ struct mm_struct *mm_alloc(void)
 		return NULL;
 
 	memset(mm, 0, sizeof(*mm));
-	return mm_init(mm, current);
+	return mm_init(mm, current, current_user_ns());
 }
 
 /*
@@ -847,6 +849,7 @@ void __mmdrop(struct mm_struct *mm)
 	destroy_context(mm);
 	mmu_notifier_mm_destroy(mm);
 	check_mm(mm);
+	put_user_ns(mm->user_ns);
 	free_mm(mm);
 }
 EXPORT_SYMBOL_GPL(__mmdrop);
@@ -1128,7 +1131,7 @@ static struct mm_struct *dup_mm(struct task_struct *tsk)
 
 	memcpy(mm, oldmm, sizeof(*mm));
 
-	if (!mm_init(mm, tsk))
+	if (!mm_init(mm, tsk, mm->user_ns))
 		goto fail_nomem;
 
 	err = dup_mmap(mm, oldmm);
diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index e6474f7272ec..49ba7c1ade9d 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -27,6 +27,35 @@
 #include <linux/cn_proc.h>
 #include <linux/compat.h>
 
+/*
+ * Access another process' address space via ptrace.
+ * Source/target buffer must be kernel space,
+ * Do not walk the page table directly, use get_user_pages
+ */
+int ptrace_access_vm(struct task_struct *tsk, unsigned long addr,
+		     void *buf, int len, unsigned int gup_flags)
+{
+	struct mm_struct *mm;
+	int ret;
+
+	mm = get_task_mm(tsk);
+	if (!mm)
+		return 0;
+
+	if (!tsk->ptrace ||
+	    (current != tsk->parent) ||
+	    ((get_dumpable(mm) != SUID_DUMP_USER) &&
+	     !ptracer_capable(tsk, mm->user_ns))) {
+		mmput(mm);
+		return 0;
+	}
+
+	ret = __access_remote_vm(tsk, mm, addr, buf, len, gup_flags);
+	mmput(mm);
+
+	return ret;
+}
+
 
 /*
  * ptrace a task: make the debugger its new parent and
@@ -39,6 +68,9 @@ void __ptrace_link(struct task_struct *child, struct task_struct *new_parent)
 	BUG_ON(!list_empty(&child->ptrace_entry));
 	list_add(&child->ptrace_entry, &new_parent->ptraced);
 	child->parent = new_parent;
+	rcu_read_lock();
+	child->ptracer_cred = get_cred(__task_cred(new_parent));
+	rcu_read_unlock();
 }
 
 /**
@@ -71,12 +103,16 @@ void __ptrace_link(struct task_struct *child, struct task_struct *new_parent)
  */
 void __ptrace_unlink(struct task_struct *child)
 {
+	const struct cred *old_cred;
 	BUG_ON(!child->ptrace);
 
 	clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
 
 	child->parent = child->real_parent;
 	list_del_init(&child->ptrace_entry);
+	old_cred = child->ptracer_cred;
+	child->ptracer_cred = NULL;
+	put_cred(old_cred);
 
 	spin_lock(&child->sighand->siglock);
 	child->ptrace = 0;
@@ -220,7 +256,7 @@ static int ptrace_has_cap(struct user_namespace *ns, unsigned int mode)
 static int __ptrace_may_access(struct task_struct *task, unsigned int mode)
 {
 	const struct cred *cred = current_cred(), *tcred;
-	int dumpable = 0;
+	struct mm_struct *mm;
 	kuid_t caller_uid;
 	kgid_t caller_gid;
 
@@ -271,16 +307,11 @@ static int __ptrace_may_access(struct task_struct *task, unsigned int mode)
 	return -EPERM;
 ok:
 	rcu_read_unlock();
-	smp_rmb();
-	if (task->mm)
-		dumpable = get_dumpable(task->mm);
-	rcu_read_lock();
-	if (dumpable != SUID_DUMP_USER &&
-	    !ptrace_has_cap(__task_cred(task)->user_ns, mode)) {
-		rcu_read_unlock();
-		return -EPERM;
-	}
-	rcu_read_unlock();
+	mm = task->mm;
+	if (mm &&
+	    ((get_dumpable(mm) != SUID_DUMP_USER) &&
+	     !ptrace_has_cap(mm->user_ns, mode)))
+	    return -EPERM;
 
 	return security_ptrace_access_check(task, mode);
 }
@@ -344,10 +375,6 @@ static int ptrace_attach(struct task_struct *task, long request,
 
 	if (seize)
 		flags |= PT_SEIZED;
-	rcu_read_lock();
-	if (ns_capable(__task_cred(task)->user_ns, CAP_SYS_PTRACE))
-		flags |= PT_PTRACE_CAP;
-	rcu_read_unlock();
 	task->ptrace = flags;
 
 	__ptrace_link(task, current);
@@ -537,7 +564,8 @@ int ptrace_readdata(struct task_struct *tsk, unsigned long src, char __user *dst
 		int this_len, retval;
 
 		this_len = (len > sizeof(buf)) ? sizeof(buf) : len;
-		retval = access_process_vm(tsk, src, buf, this_len, FOLL_FORCE);
+		retval = ptrace_access_vm(tsk, src, buf, this_len, FOLL_FORCE);
+
 		if (!retval) {
 			if (copied)
 				break;
@@ -564,7 +592,7 @@ int ptrace_writedata(struct task_struct *tsk, char __user *src, unsigned long ds
 		this_len = (len > sizeof(buf)) ? sizeof(buf) : len;
 		if (copy_from_user(buf, src, this_len))
 			return -EFAULT;
-		retval = access_process_vm(tsk, dst, buf, this_len,
+		retval = ptrace_access_vm(tsk, dst, buf, this_len,
 				FOLL_FORCE | FOLL_WRITE);
 		if (!retval) {
 			if (copied)
@@ -1128,7 +1156,7 @@ int generic_ptrace_peekdata(struct task_struct *tsk, unsigned long addr,
 	unsigned long tmp;
 	int copied;
 
-	copied = access_process_vm(tsk, addr, &tmp, sizeof(tmp), FOLL_FORCE);
+	copied = ptrace_access_vm(tsk, addr, &tmp, sizeof(tmp), FOLL_FORCE);
 	if (copied != sizeof(tmp))
 		return -EIO;
 	return put_user(tmp, (unsigned long __user *)data);
@@ -1139,7 +1167,7 @@ int generic_ptrace_pokedata(struct task_struct *tsk, unsigned long addr,
 {
 	int copied;
 
-	copied = access_process_vm(tsk, addr, &data, sizeof(data),
+	copied = ptrace_access_vm(tsk, addr, &data, sizeof(data),
 			FOLL_FORCE | FOLL_WRITE);
 	return (copied == sizeof(data)) ? 0 : -EIO;
 }
@@ -1157,7 +1185,7 @@ int compat_ptrace_request(struct task_struct *child, compat_long_t request,
 	switch (request) {
 	case PTRACE_PEEKTEXT:
 	case PTRACE_PEEKDATA:
-		ret = access_process_vm(child, addr, &word, sizeof(word),
+		ret = ptrace_access_vm(child, addr, &word, sizeof(word),
 				FOLL_FORCE);
 		if (ret != sizeof(word))
 			ret = -EIO;
@@ -1167,7 +1195,7 @@ int compat_ptrace_request(struct task_struct *child, compat_long_t request,
 
 	case PTRACE_POKETEXT:
 	case PTRACE_POKEDATA:
-		ret = access_process_vm(child, addr, &data, sizeof(data),
+		ret = ptrace_access_vm(child, addr, &data, sizeof(data),
 				FOLL_FORCE | FOLL_WRITE);
 		ret = (ret != sizeof(data) ? -EIO : 0);
 		break;
diff --git a/mm/init-mm.c b/mm/init-mm.c
index a56a851908d2..975e49f00f34 100644
--- a/mm/init-mm.c
+++ b/mm/init-mm.c
@@ -6,6 +6,7 @@
 #include <linux/cpumask.h>
 
 #include <linux/atomic.h>
+#include <linux/user_namespace.h>
 #include <asm/pgtable.h>
 #include <asm/mmu.h>
 
@@ -21,5 +22,6 @@ struct mm_struct init_mm = {
 	.mmap_sem	= __RWSEM_INITIALIZER(init_mm.mmap_sem),
 	.page_table_lock =  __SPIN_LOCK_UNLOCKED(init_mm.page_table_lock),
 	.mmlist		= LIST_HEAD_INIT(init_mm.mmlist),
+	.user_ns	= &init_user_ns,
 	INIT_MM_CONTEXT(init_mm)
 };
diff --git a/mm/memory.c b/mm/memory.c
index c264f7cd3e47..08d8da39de28 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3904,7 +3904,7 @@ EXPORT_SYMBOL_GPL(generic_access_phys);
  * Access another process' address space as given in mm.  If non-NULL, use the
  * given task for page fault accounting.
  */
-static int __access_remote_vm(struct task_struct *tsk, struct mm_struct *mm,
+int __access_remote_vm(struct task_struct *tsk, struct mm_struct *mm,
 		unsigned long addr, void *buf, int len, unsigned int gup_flags)
 {
 	struct vm_area_struct *vma;
diff --git a/mm/nommu.c b/mm/nommu.c
index 9720e0bab029..27bc543128e5 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -1808,7 +1808,7 @@ void filemap_map_pages(struct fault_env *fe,
 }
 EXPORT_SYMBOL(filemap_map_pages);
 
-static int __access_remote_vm(struct task_struct *tsk, struct mm_struct *mm,
+int __access_remote_vm(struct task_struct *tsk, struct mm_struct *mm,
 		unsigned long addr, void *buf, int len, unsigned int gup_flags)
 {
 	struct vm_area_struct *vma;
diff --git a/security/integrity/evm/evm_crypto.c b/security/integrity/evm/evm_crypto.c
index bf663915412e..d7f282d75cc1 100644
--- a/security/integrity/evm/evm_crypto.c
+++ b/security/integrity/evm/evm_crypto.c
@@ -151,8 +151,16 @@ static void hmac_add_misc(struct shash_desc *desc, struct inode *inode,
 	memset(&hmac_misc, 0, sizeof(hmac_misc));
 	hmac_misc.ino = inode->i_ino;
 	hmac_misc.generation = inode->i_generation;
-	hmac_misc.uid = from_kuid(inode->i_sb->s_user_ns, inode->i_uid);
-	hmac_misc.gid = from_kgid(inode->i_sb->s_user_ns, inode->i_gid);
+	/* The hmac uid and gid must be encoded in the initial user
+	 * namespace (not the filesystems user namespace) as encoding
+	 * them in the filesystems user namespace allows an attack
+	 * where first they are written in an unprivileged fuse mount
+	 * of a filesystem and then the system is tricked to mount the
+	 * filesystem for real on next boot and trust it because
+	 * everything is signed.
+	 */
+	hmac_misc.uid = from_kuid(&init_user_ns, inode->i_uid);
+	hmac_misc.gid = from_kgid(&init_user_ns, inode->i_gid);
 	hmac_misc.mode = inode->i_mode;
 	crypto_shash_update(desc, (const u8 *)&hmac_misc, sizeof(hmac_misc));
 	if (evm_hmac_attrs & EVM_ATTR_FSUUID)