Merge 4.4.92 into android-4.4

Changes in 4.4.92
	usb: gadget: inode.c: fix unbalanced spin_lock in ep0_write
	USB: gadgetfs: Fix crash caused by inadequate synchronization
	USB: gadgetfs: fix copy_to_user while holding spinlock
	usb: gadget: udc: atmel: set vbus irqflags explicitly
	usb-storage: unusual_devs entry to fix write-access regression for Seagate external drives
	usb: renesas_usbhs: fix the BCLR setting condition for non-DCP pipe
	usb: renesas_usbhs: fix usbhsf_fifo_clear() for RX direction
	ALSA: usb-audio: Check out-of-bounds access by corrupted buffer descriptor
	usb: pci-quirks.c: Corrected timeout values used in handshake
	USB: dummy-hcd: fix connection failures (wrong speed)
	USB: dummy-hcd: fix infinite-loop resubmission bug
	USB: dummy-hcd: Fix erroneous synchronization change
	USB: devio: Don't corrupt user memory
	usb: gadget: mass_storage: set msg_registered after msg registered
	USB: g_mass_storage: Fix deadlock when driver is unbound
	lsm: fix smack_inode_removexattr and xattr_getsecurity memleak
	ALSA: compress: Remove unused variable
	ALSA: usx2y: Suppress kernel warning at page allocation failures
	driver core: platform: Don't read past the end of "driver_override" buffer
	Drivers: hv: fcopy: restore correct transfer length
	stm class: Fix a use-after-free
	ftrace: Fix kmemleak in unregister_ftrace_graph
	HID: i2c-hid: allocate hid buffers for real worst case
	iwlwifi: add workaround to disable wide channels in 5GHz
	scsi: sd: Do not override max_sectors_kb sysfs setting
	USB: uas: fix bug in handling of alternate settings
	USB: core: harden cdc_parse_cdc_header
	usb: Increase quirk delay for USB devices
	USB: fix out-of-bounds in usb_set_configuration
	xhci: fix finding correct bus_state structure for USB 3.1 hosts
	iio: adc: twl4030: Fix an error handling path in 'twl4030_madc_probe()'
	iio: adc: twl4030: Disable the vusb3v1 rugulator in the error handling path of 'twl4030_madc_probe()'
	iio: ad_sigma_delta: Implement a dedicated reset function
	staging: iio: ad7192: Fix - use the dedicated reset function avoiding dma from stack.
	iio: core: Return error for failed read_reg
	iio: ad7793: Fix the serial interface reset
	iio: adc: mcp320x: Fix readout of negative voltages
	iio: adc: mcp320x: Fix oops on module unload
	uwb: properly check kthread_run return value
	uwb: ensure that endpoint is interrupt
	brcmfmac: setup passive scan if requested by user-space
	drm/i915/bios: ignore HDMI on port A
	nvme: protect against simultaneous shutdown invocations
	sched/cpuset/pm: Fix cpuset vs. suspend-resume bugs
	ext4: fix data corruption for mmap writes
	ext4: Don't clear SGID when inheriting ACLs
	ext4: don't allow encrypted operations without keys
	Linux 4.4.92

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

1 files changed, 19 insertions, 5 deletions

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 2ac719290869..530e790f22e0 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -1964,15 +1964,29 @@ static int ext4_writepage(struct page *page,
 static int mpage_submit_page(struct mpage_da_data *mpd, struct page *page)
 {
 	int len;
-	loff_t size = i_size_read(mpd->inode);
+	loff_t size;
 	int err;
 
 	BUG_ON(page->index != mpd->first_page);
-	if (page->index == size >> PAGE_CACHE_SHIFT)
-		len = size & ~PAGE_CACHE_MASK;
-	else
-		len = PAGE_CACHE_SIZE;
 	clear_page_dirty_for_io(page);
+	/*
+	 * We have to be very careful here!  Nothing protects writeback path
+	 * against i_size changes and the page can be writeably mapped into
+	 * page tables. So an application can be growing i_size and writing
+	 * data through mmap while writeback runs. clear_page_dirty_for_io()
+	 * write-protects our page in page tables and the page cannot get
+	 * written to again until we release page lock. So only after
+	 * clear_page_dirty_for_io() we are safe to sample i_size for
+	 * ext4_bio_write_page() to zero-out tail of the written page. We rely
+	 * on the barrier provided by TestClearPageDirty in
+	 * clear_page_dirty_for_io() to make sure i_size is really sampled only
+	 * after page tables are updated.
+	 */
+	size = i_size_read(mpd->inode);
+	if (page->index == size >> PAGE_SHIFT)
+		len = size & ~PAGE_MASK;
+	else
+		len = PAGE_SIZE;
 	err = ext4_bio_write_page(&mpd->io_submit, page, len, mpd->wbc, false);
 	if (!err)
 		mpd->wbc->nr_to_write--;