Merge tag 'v4.7-rc6' into patchwork

Linux 4.7-rc6

* tag 'v4.7-rc6': (1245 commits)
  Linux 4.7-rc6
  ovl: warn instead of error if d_type is not supported
  MIPS: Fix possible corruption of cache mode by mprotect.
  locks: use file_inode()
  usb: dwc3: st: Use explicit reset_control_get_exclusive() API
  phy: phy-stih407-usb: Use explicit reset_control_get_exclusive() API
  phy: miphy28lp: Inform the reset framework that our reset line may be shared
  namespace: update event counter when umounting a deleted dentry
  9p: use file_dentry()
  lockd: unregister notifier blocks if the service fails to come up completely
  ACPI,PCI,IRQ: correct operator precedence
  fuse: serialize dirops by default
  drm/i915: Fix missing unlock on error in i915_ppgtt_info()
  powerpc: Initialise pci_io_base as early as possible
  mfd: da9053: Fix compiler warning message for uninitialised variable
  mfd: max77620: Fix FPS switch statements
  phy: phy-stih407-usb: Inform the reset framework that our reset line may be shared
  usb: dwc3: st: Inform the reset framework that our reset line may be shared
  usb: host: ehci-st: Inform the reset framework that our reset line may be shared
  usb: host: ohci-st: Inform the reset framework that our reset line may be shared
  ...

1 files changed, 11 insertions, 3 deletions

diff --git a/kernel/futex.c b/kernel/futex.c
index ee25f5ba4aca..33664f70e2d2 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -469,7 +469,7 @@ get_futex_key(u32 __user *uaddr, int fshared, union futex_key *key, int rw)
 {
 	unsigned long address = (unsigned long)uaddr;
 	struct mm_struct *mm = current->mm;
-	struct page *page;
+	struct page *page, *tail;
 	struct address_space *mapping;
 	int err, ro = 0;
 
@@ -530,7 +530,15 @@ again:
 	 * considered here and page lock forces unnecessarily serialization
 	 * From this point on, mapping will be re-verified if necessary and
 	 * page lock will be acquired only if it is unavoidable
-	 */
+	 *
+	 * Mapping checks require the head page for any compound page so the
+	 * head page and mapping is looked up now. For anonymous pages, it
+	 * does not matter if the page splits in the future as the key is
+	 * based on the address. For filesystem-backed pages, the tail is
+	 * required as the index of the page determines the key. For
+	 * base pages, there is no tail page and tail == page.
+	 */
+	tail = page;
 	page = compound_head(page);
 	mapping = READ_ONCE(page->mapping);
 
@@ -654,7 +662,7 @@ again:
 
 		key->both.offset |= FUT_OFF_INODE; /* inode-based key */
 		key->shared.inode = inode;
-		key->shared.pgoff = basepage_index(page);
+		key->shared.pgoff = basepage_index(tail);
 		rcu_read_unlock();
 	}