Merge 4.4.148 into android-4.4-p

Changes in 4.4.148
	ext4: fix check to prevent initializing reserved inodes
	tpm: fix race condition in tpm_common_write()
	ipv4+ipv6: Make INET*_ESP select CRYPTO_ECHAINIV
	fork: unconditionally clear stack on fork
	parisc: Enable CONFIG_MLONGCALLS by default
	parisc: Define mb() and add memory barriers to assembler unlock sequences
	xen/netfront: don't cache skb_shinfo()
	ACPI / LPSS: Add missing prv_offset setting for byt/cht PWM devices
	scsi: sr: Avoid that opening a CD-ROM hangs with runtime power management enabled
	root dentries need RCU-delayed freeing
	fix mntput/mntput race
	fix __legitimize_mnt()/mntput() race
	IB/core: Make testing MR flags for writability a static inline function
	IB/mlx4: Mark user MR as writable if actual virtual memory is writable
	IB/ocrdma: fix out of bounds access to local buffer
	ARM: dts: imx6sx: fix irq for pcie bridge
	x86/paravirt: Fix spectre-v2 mitigations for paravirt guests
	x86/speculation: Protect against userspace-userspace spectreRSB
	kprobes/x86: Fix %p uses in error messages
	x86/irqflags: Provide a declaration for native_save_fl
	x86/speculation/l1tf: Increase 32bit PAE __PHYSICAL_PAGE_SHIFT
	x86/mm: Move swap offset/type up in PTE to work around erratum
	x86/mm: Fix swap entry comment and macro
	mm: x86: move _PAGE_SWP_SOFT_DIRTY from bit 7 to bit 1
	x86/speculation/l1tf: Change order of offset/type in swap entry
	x86/speculation/l1tf: Protect swap entries against L1TF
	x86/speculation/l1tf: Protect PROT_NONE PTEs against speculation
	x86/speculation/l1tf: Make sure the first page is always reserved
	x86/speculation/l1tf: Add sysfs reporting for l1tf
	mm: Add vm_insert_pfn_prot()
	mm: fix cache mode tracking in vm_insert_mixed()
	x86/speculation/l1tf: Disallow non privileged high MMIO PROT_NONE mappings
	x86/speculation/l1tf: Limit swap file size to MAX_PA/2
	x86/bugs: Move the l1tf function and define pr_fmt properly
	x86/speculation/l1tf: Extend 64bit swap file size limit
	x86/cpufeatures: Add detection of L1D cache flush support.
	x86/speculation/l1tf: Protect PAE swap entries against L1TF
	x86/speculation/l1tf: Fix up pte->pfn conversion for PAE
	x86/speculation/l1tf: Invert all not present mappings
	x86/speculation/l1tf: Make pmd/pud_mknotpresent() invert
	x86/mm/pat: Make set_memory_np() L1TF safe
	x86/mm/kmmio: Make the tracer robust against L1TF
	x86/speculation/l1tf: Fix up CPU feature flags
	x86/init: fix build with CONFIG_SWAP=n
	x86/speculation/l1tf: Unbreak !__HAVE_ARCH_PFN_MODIFY_ALLOWED architectures
	Linux 4.4.148

Change-Id: Id593840e382389d43e5e54f9d1cfa1d679d8d8be
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>

1 files changed, 26 insertions, 2 deletions

diff --git a/fs/namespace.c b/fs/namespace.c
index ce282400d13e..996e1046e1ff 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -605,12 +605,21 @@ int __legitimize_mnt(struct vfsmount *bastard, unsigned seq)
 		return 0;
 	mnt = real_mount(bastard);
 	mnt_add_count(mnt, 1);
+	smp_mb();			// see mntput_no_expire()
 	if (likely(!read_seqretry(&mount_lock, seq)))
 		return 0;
 	if (bastard->mnt_flags & MNT_SYNC_UMOUNT) {
 		mnt_add_count(mnt, -1);
 		return 1;
 	}
+	lock_mount_hash();
+	if (unlikely(bastard->mnt_flags & MNT_DOOMED)) {
+		mnt_add_count(mnt, -1);
+		unlock_mount_hash();
+		return 1;
+	}
+	unlock_mount_hash();
+	/* caller will mntput() */
 	return -1;
 }
 
@@ -1142,12 +1151,27 @@ static DECLARE_DELAYED_WORK(delayed_mntput_work, delayed_mntput);
 static void mntput_no_expire(struct mount *mnt)
 {
 	rcu_read_lock();
-	mnt_add_count(mnt, -1);
-	if (likely(mnt->mnt_ns)) { /* shouldn't be the last one */
+	if (likely(READ_ONCE(mnt->mnt_ns))) {
+		/*
+		 * Since we don't do lock_mount_hash() here,
+		 * ->mnt_ns can change under us.  However, if it's
+		 * non-NULL, then there's a reference that won't
+		 * be dropped until after an RCU delay done after
+		 * turning ->mnt_ns NULL.  So if we observe it
+		 * non-NULL under rcu_read_lock(), the reference
+		 * we are dropping is not the final one.
+		 */
+		mnt_add_count(mnt, -1);
 		rcu_read_unlock();
 		return;
 	}
 	lock_mount_hash();
+	/*
+	 * make sure that if __legitimize_mnt() has not seen us grab
+	 * mount_lock, we'll see their refcount increment here.
+	 */
+	smp_mb();
+	mnt_add_count(mnt, -1);
 	if (mnt_get_count(mnt)) {
 		rcu_read_unlock();
 		unlock_mount_hash();