Merge 4.4.155 into android-4.4

Changes in 4.4.155
	net: 6lowpan: fix reserved space for single frames
	net: mac802154: tx: expand tailroom if necessary
	9p/net: Fix zero-copy path in the 9p virtio transport
	net: lan78xx: Fix misplaced tasklet_schedule() call
	spi: davinci: fix a NULL pointer dereference
	drm/i915/userptr: reject zero user_size
	powerpc/fadump: handle crash memory ranges array index overflow
	powerpc/pseries: Fix endianness while restoring of r3 in MCE handler.
	fs/9p/xattr.c: catch the error of p9_client_clunk when setting xattr failed
	9p/virtio: fix off-by-one error in sg list bounds check
	net/9p/client.c: version pointer uninitialized
	net/9p/trans_fd.c: fix race-condition by flushing workqueue before the kfree()
	x86/mm/pat: Fix L1TF stable backport for CPA, 2nd call
	dm cache metadata: save in-core policy_hint_size to on-disk superblock
	iio: ad9523: Fix displayed phase
	iio: ad9523: Fix return value for ad952x_store()
	vmw_balloon: fix inflation of 64-bit GFNs
	vmw_balloon: do not use 2MB without batching
	vmw_balloon: VMCI_DOORBELL_SET does not check status
	vmw_balloon: fix VMCI use when balloon built into kernel
	tracing: Do not call start/stop() functions when tracing_on does not change
	tracing/blktrace: Fix to allow setting same value
	kthread, tracing: Don't expose half-written comm when creating kthreads
	uprobes: Use synchronize_rcu() not synchronize_sched()
	9p: fix multiple NULL-pointer-dereferences
	PM / sleep: wakeup: Fix build error caused by missing SRCU support
	pnfs/blocklayout: off by one in bl_map_stripe()
	ARM: tegra: Fix Tegra30 Cardhu PCA954x reset
	mm/tlb: Remove tlb_remove_table() non-concurrent condition
	iommu/vt-d: Add definitions for PFSID
	iommu/vt-d: Fix dev iotlb pfsid use
	osf_getdomainname(): use copy_to_user()
	sys: don't hold uts_sem while accessing userspace memory
	userns: move user access out of the mutex
	ubifs: Fix memory leak in lprobs self-check
	Revert "UBIFS: Fix potential integer overflow in allocation"
	ubifs: Check data node size before truncate
	ubifs: Fix synced_i_size calculation for xattr inodes
	pwm: tiehrpwm: Fix disabling of output of PWMs
	fb: fix lost console when the user unplugs a USB adapter
	udlfb: set optimal write delay
	getxattr: use correct xattr length
	bcache: release dc->writeback_lock properly in bch_writeback_thread()
	perf auxtrace: Fix queue resize
	fs/quota: Fix spectre gadget in do_quotactl
	x86/io: add interface to reserve io memtype for a resource range. (v1.1)
	drm/drivers: add support for using the arch wc mapping API.
	Linux 4.4.155

Change-Id: Ie455609e00dd70d3fa723cd254f544109db8a788
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>

1 files changed, 25 insertions, 16 deletions

diff --git a/kernel/utsname_sysctl.c b/kernel/utsname_sysctl.c
index c8eac43267e9..d2b3b2973456 100644
--- a/kernel/utsname_sysctl.c
+++ b/kernel/utsname_sysctl.c
@@ -17,7 +17,7 @@
 
 #ifdef CONFIG_PROC_SYSCTL
 
-static void *get_uts(struct ctl_table *table, int write)
+static void *get_uts(struct ctl_table *table)
 {
 	char *which = table->data;
 	struct uts_namespace *uts_ns;
@@ -25,21 +25,9 @@ static void *get_uts(struct ctl_table *table, int write)
 	uts_ns = current->nsproxy->uts_ns;
 	which = (which - (char *)&init_uts_ns) + (char *)uts_ns;
 
-	if (!write)
-		down_read(&uts_sem);
-	else
-		down_write(&uts_sem);
 	return which;
 }
 
-static void put_uts(struct ctl_table *table, int write, void *which)
-{
-	if (!write)
-		up_read(&uts_sem);
-	else
-		up_write(&uts_sem);
-}
-
 /*
  *	Special case of dostring for the UTS structure. This has locks
  *	to observe. Should this be in kernel/sys.c ????
@@ -49,13 +37,34 @@ static int proc_do_uts_string(struct ctl_table *table, int write,
 {
 	struct ctl_table uts_table;
 	int r;
+	char tmp_data[__NEW_UTS_LEN + 1];
+
 	memcpy(&uts_table, table, sizeof(uts_table));
-	uts_table.data = get_uts(table, write);
+	uts_table.data = tmp_data;
+
+	/*
+	 * Buffer the value in tmp_data so that proc_dostring() can be called
+	 * without holding any locks.
+	 * We also need to read the original value in the write==1 case to
+	 * support partial writes.
+	 */
+	down_read(&uts_sem);
+	memcpy(tmp_data, get_uts(table), sizeof(tmp_data));
+	up_read(&uts_sem);
 	r = proc_dostring(&uts_table, write, buffer, lenp, ppos);
-	put_uts(table, write, uts_table.data);
 
-	if (write)
+	if (write) {
+		/*
+		 * Write back the new value.
+		 * Note that, since we dropped uts_sem, the result can
+		 * theoretically be incorrect if there are two parallel writes
+		 * at non-zero offsets to the same sysctl.
+		 */
+		down_write(&uts_sem);
+		memcpy(get_uts(table), tmp_data, sizeof(tmp_data));
+		up_write(&uts_sem);
 		proc_sys_poll_notify(table->poll);
+	}
 
 	return r;
 }