user/sven/linux.git, branch v3.18.24

Linux 3.18.24

2015-10-31T20:39:51Z

Signed-off-by: Sasha Levin

tty: fix stall caused by missing memory barrier in drivers/tty/n_tty.c

2015-10-31T13:00:00Z

[ Upstream commit e81107d4c6bd098878af9796b24edc8d4a9524fd ] My colleague ran into a program stall on a x86_64 server, where n_tty_read() was waiting for data even if there was data in the buffer in the pty. kernel stack for the stuck process looks like below. #0 [ffff88303d107b58] __schedule at ffffffff815c4b20 #1 [ffff88303d107bd0] schedule at ffffffff815c513e #2 [ffff88303d107bf0] schedule_timeout at ffffffff815c7818 #3 [ffff88303d107ca0] wait_woken at ffffffff81096bd2 #4 [ffff88303d107ce0] n_tty_read at ffffffff8136fa23 #5 [ffff88303d107dd0] tty_read at ffffffff81368013 #6 [ffff88303d107e20] __vfs_read at ffffffff811a3704 #7 [ffff88303d107ec0] vfs_read at ffffffff811a3a57 #8 [ffff88303d107f00] sys_read at ffffffff811a4306 #9 [ffff88303d107f50] entry_SYSCALL_64_fastpath at ffffffff815c86d7 There seems to be two problems causing this issue. First, in drivers/tty/n_tty.c, __receive_buf() stores the data and updates ldata->commit_head using smp_store_release() and then checks the wait queue using waitqueue_active(). However, since there is no memory barrier, __receive_buf() could return without calling wake_up_interactive_poll(), and at the same time, n_tty_read() could start to wait in wait_woken() as in the following chart. __receive_buf() n_tty_read() ------------------------------------------------------------------------ if (waitqueue_active(&tty->read_wait)) /* Memory operations issued after the RELEASE may be completed before the RELEASE operation has completed */ add_wait_queue(&tty->read_wait, &wait); ... if (!input_available_p(tty, 0)) { smp_store_release(&ldata->commit_head, ldata->read_head); ... timeout = wait_woken(&wait, TASK_INTERRUPTIBLE, timeout); ------------------------------------------------------------------------ The second problem is that n_tty_read() also lacks a memory barrier call and could also cause __receive_buf() to return without calling wake_up_interactive_poll(), and n_tty_read() to wait in wait_woken() as in the chart below. __receive_buf() n_tty_read() ------------------------------------------------------------------------ spin_lock_irqsave(&q->lock, flags); /* from add_wait_queue() */ ... if (!input_available_p(tty, 0)) { /* Memory operations issued after the RELEASE may be completed before the RELEASE operation has completed */ smp_store_release(&ldata->commit_head, ldata->read_head); if (waitqueue_active(&tty->read_wait)) __add_wait_queue(q, wait); spin_unlock_irqrestore(&q->lock,flags); /* from add_wait_queue() */ ... timeout = wait_woken(&wait, TASK_INTERRUPTIBLE, timeout); ------------------------------------------------------------------------ There are also other places in drivers/tty/n_tty.c which have similar calls to waitqueue_active(), so instead of adding many memory barrier calls, this patch simply removes the call to waitqueue_active(), leaving just wake_up*() behind. This fixes both problems because, even though the memory access before or after the spinlocks in both wake_up*() and add_wait_queue() can sneak into the critical section, it cannot go past it and the critical section assures that they will be serialized (please see "INTER-CPU ACQUIRING BARRIER EFFECTS" in Documentation/memory-barriers.txt for a better explanation). Moreover, the resulting code is much simpler. Latency measurement using a ping-pong test over a pty doesn't show any visible performance drop. Signed-off-by: Kosuke Tatsukawa Cc: stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin

Revert "tty: fix stall caused by missing memory barrier in drivers/tty/n_tty.c"

2015-10-31T12:54:32Z

This reverts commit af32cc7bde6304dac92e6a74fe4b2cc8120cb29a. The commit was incorrectly backported and was causing hangs. Reported-by: Corey Wright Signed-off-by: Sasha Levin

Linux 3.18.23

2015-10-29T02:49:46Z

Signed-off-by: Sasha Levin

x86: Init per-cpu shadow copy of CR4 on 32-bit CPUs too

2015-10-28T20:20:25Z

[ Upstream commit 5b2bdbc84556774afbe11bcfd24c2f6411cfa92b ] Commit: 1e02ce4cccdc ("x86: Store a per-cpu shadow copy of CR4") added a shadow CR4 such that reads and writes that do not modify the CR4 execute much faster than always reading the register itself. The change modified cpu_init() in common.c, so that the shadow CR4 gets initialized before anything uses it. Unfortunately, there's two cpu_init()s in common.c. There's one for 64-bit and one for 32-bit. The commit only added the shadow init to the 64-bit path, but the 32-bit path needs the init too. Link: http://lkml.kernel.org/r/20150227125208.71c36402@gandalf.local.home Fixes: 1e02ce4cccdc "x86: Store a per-cpu shadow copy of CR4" Signed-off-by: Steven Rostedt Acked-by: Andy Lutomirski Cc: Peter Zijlstra (Intel) Cc: Linus Torvalds Link: http://lkml.kernel.org/r/20150227145019.2bdd4354@gandalf.local.home Signed-off-by: Ingo Molnar Signed-off-by: Sasha Levin

3w-9xxx: don't unmap bounce buffered commands

2015-10-28T07:52:26Z

[ Upstream commit 15e3d5a285ab9283136dba34bbf72886d9146706 ] 3w controller don't dma map small single SGL entry commands but instead bounce buffer them. Add a helper to identify these commands and don't call scsi_dma_unmap for them. Based on an earlier patch from James Bottomley. Fixes: 118c85 ("3w-9xxx: fix command completion race") Reported-by: Tóth Attila Tested-by: Tóth Attila Signed-off-by: Christoph Hellwig Acked-by: Adam Radford Signed-off-by: James Bottomley Signed-off-by: Sasha Levin

fib_rules: Fix dump_rules() not to exit early

2015-10-28T07:52:10Z

[ Upstream commit 8ea4b34355189e1f1eacaf2d825f2dce776b3b9c ] Backports of 41fc014332d9 ("fib_rules: fix fib rule dumps across multiple skbs") introduced a regression in "ip rule show" - it ends up dumping the first rule over and over and never exiting, because 3.19 and earlier are missing commit 053c095a82cf ("netlink: make nlmsg_end() and genlmsg_end() void"), so fib_nl_fill_rule() ends up returning skb->len (i.e. > 0) in the success case. Fix this by checking the return code for < 0 instead of != 0. Signed-off-by: Roland Dreier Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin

vfs: Test for and handle paths that are unreachable from their mnt_root

2015-10-28T02:14:58Z

[ Upstream commit 397d425dc26da728396e66d392d5dcb8dac30c37 ] In rare cases a directory can be renamed out from under a bind mount. In those cases without special handling it becomes possible to walk up the directory tree to the root dentry of the filesystem and down from the root dentry to every other file or directory on the filesystem. Like division by zero .. from an unconnected path can not be given a useful semantic as there is no predicting at which path component the code will realize it is unconnected. We certainly can not match the current behavior as the current behavior is a security hole. Therefore when encounting .. when following an unconnected path return -ENOENT. - Add a function path_connected to verify path->dentry is reachable from path->mnt.mnt_root. AKA to validate that rename did not do something nasty to the bind mount. To avoid races path_connected must be called after following a path component to it's next path component. Signed-off-by: "Eric W. Biederman" Signed-off-by: Al Viro Signed-off-by: Sasha Levin

md: flush ->event_work before stopping array.

2015-10-28T02:14:57Z

[ Upstream commit ee5d004fd0591536a061451eba2b187092e9127c ] The 'event_work' worker used by dm-raid may still be running when the array is stopped. This can result in an oops. So flush the workqueue on which it is run after detaching and before destroying the device. Reported-by: Heinz Mauelshagen Signed-off-by: NeilBrown Cc: stable@vger.kernel.org (2.6.38+ please delay 2 weeks after -final release) Fixes: 9d09e663d550 ("dm: raid456 basic support") Signed-off-by: Sasha Levin

x86/nmi/64: Fix a paravirt stack-clobbering bug in the NMI code

2015-10-28T02:14:57Z

[ Upstream commit 83c133cf11fb0e68a51681447e372489f052d40e ] The NMI entry code that switches to the normal kernel stack needs to be very careful not to clobber any extra stack slots on the NMI stack. The code is fine under the assumption that SWAPGS is just a normal instruction, but that assumption isn't really true. Use SWAPGS_UNSAFE_STACK instead. This is part of a fix for some random crashes that Sasha saw. Fixes: 9b6e6a8334d5 ("x86/nmi/64: Switch stacks on userspace NMI entry") Reported-and-tested-by: Sasha Levin Signed-off-by: Andy Lutomirski Cc: stable@vger.kernel.org Link: http://lkml.kernel.org/r/974bc40edffdb5c2950a5c4977f821a446b76178.1442791737.git.luto@kernel.org Signed-off-by: Thomas Gleixner Signed-off-by: Sasha Levin