Merge 4.4.281 into android-4.4-p

Changes in 4.4.281
	ALSA: seq: Fix racy deletion of subscriber
	scsi: sr: Return correct event when media event code is 3
	media: videobuf2-core: dequeue if start_streaming fails
	net: natsemi: Fix missing pci_disable_device() in probe and remove
	mips: Fix non-POSIX regexp
	bnx2x: fix an error code in bnx2x_nic_load()
	net: pegasus: fix uninit-value in get_interrupt_interval
	net: vxge: fix use-after-free in vxge_device_unregister
	Bluetooth: defer cleanup of resources in hci_unregister_dev()
	USB: serial: option: add Telit FD980 composition 0x1056
	USB: serial: ch341: fix character loss at high transfer rates
	USB: serial: ftdi_sio: add device ID for Auto-M3 OP-COM v2
	scripts/tracing: fix the bug that can't parse raw_trace_func
	media: rtl28xxu: fix zero-length control request
	serial: 8250: Mask out floating 16/32-bit bus bits
	MIPS: Malta: Do not byte-swap accesses to the CBUS UART
	pcmcia: i82092: fix a null pointer dereference bug
	reiserfs: add check for root_inode in reiserfs_fill_super
	reiserfs: check directory items on read from disk
	alpha: Send stop IPI to send to online CPUs
	net/qla3xxx: fix schedule while atomic in ql_wait_for_drvr_lock and ql_adapter_reset
	pipe: increase minimum default pipe size to 2 pages
	USB:ehci:fix Kunpeng920 ehci hardware problem
	net: xilinx_emaclite: Do not print real IOMEM pointer
	ovl: prevent private clone if bind mount is not allowed
	Linux 4.4.281

Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Change-Id: I23014eec5c0648b030387cc4469a1cdfaa2c14a1

1 files changed, 16 insertions, 1 deletions

diff --git a/fs/pipe.c b/fs/pipe.c
index 6534470a6c19..37a003b645ef 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -28,6 +28,21 @@
 #include "internal.h"
 
 /*
+ * New pipe buffers will be restricted to this size while the user is exceeding
+ * their pipe buffer quota. The general pipe use case needs at least two
+ * buffers: one for data yet to be read, and one for new data. If this is less
+ * than two, then a write to a non-empty pipe may block even if the pipe is not
+ * full. This can occur with GNU make jobserver or similar uses of pipes as
+ * semaphores: multiple processes may be waiting to write tokens back to the
+ * pipe before reading tokens: https://lore.kernel.org/lkml/1628086770.5rn8p04n6j.none@localhost/.
+ *
+ * Users can reduce their pipe buffers with F_SETPIPE_SZ below this at their
+ * own risk, namely: pipe writes to non-full pipes may block until the pipe is
+ * emptied.
+ */
+#define PIPE_MIN_DEF_BUFFERS 2
+
+/*
  * The max size that a non-root user is allowed to grow the pipe. Can
  * be set by root in /proc/sys/fs/pipe-max-size
  */
@@ -621,7 +636,7 @@ struct pipe_inode_info *alloc_pipe_info(void)
 
 		if (!too_many_pipe_buffers_hard(user)) {
 			if (too_many_pipe_buffers_soft(user))
-				pipe_bufs = 1;
+				pipe_bufs = PIPE_MIN_DEF_BUFFERS;
 			pipe->bufs = kzalloc(sizeof(struct pipe_buffer) * pipe_bufs, GFP_KERNEL);
 		}