Stack guard page is a useful feature to reduce a risk of stack smashing
into a different mapping. We have been using a single page gap which
is sufficient to prevent having stack adjacent to a different mapping.
But this seems to be insufficient in the light of the stack usage in
userspace. E.g. glibc uses as large as 64kB alloca() in many commonly
used functions. Others use constructs liks gid_t buffer[NGROUPS_MAX]
which is 256kB or stack strings with MAX_ARG_STRLEN.

This will become especially dangerous for suid binaries and the default
no limit for the stack size limit because those applications can be
tricked to consume a large portion of the stack and a single glibc call
could jump over the guard page. These attacks are not theoretical,
unfortunatelly.

Make those attacks less probable by increasing the stack guard gap
to 1MB (on systems with 4k pages; but make it depend on the page size
because systems with larger base pages might cap stack allocations in
the PAGE_SIZE units) which should cover larger alloca() and VLA stack
allocations. It is obviously not a full fix because the problem is
somehow inherent, but it should reduce attack space a lot.

One could argue that the gap size should be configurable from userspace,
but that can be done later when somebody finds that the new 1MB is wrong
for some special case applications.  For now, add a kernel command line
option (stack_guard_gap) to specify the stack gap size (in page units).

Implementation wise, first delete all the old code for stack guard page:
because although we could get away with accounting one extra page in a
stack vma, accounting a larger gap can break userspace - case in point,
a program run with "ulimit -S -v 20000" failed when the 1MB gap was
counted for RLIMIT_AS; similar problems could come with RLIMIT_MLOCK
and strict non-overcommit mode.

Instead of keeping gap inside the stack vma, maintain the stack guard
gap as a gap between vmas: using vm_start_gap() in place of vm_start
(or vm_end_gap() in place of vm_end if VM_GROWSUP) in just those few
places which need to respect the gap - mainly arch_get_unmapped_area(),
and and the vma tree's subtree_gap support for that.

Original-patch-by: Oleg Nesterov <oleg@redhat.com>
Original-patch-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Hugh Dickins <hughd@google.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Tested-by: Helge Deller <deller@gmx.de> # parisc
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Pull networking fixes from David Miller:

 1) The netlink attribute passed in to dev_set_alias() is not
    necessarily NULL terminated, don't use strlcpy() on it. From
    Alexander Potapenko.

 2) Fix implementation of atomics in arm64 bpf JIT, from Daniel
    Borkmann.

 3) Correct the release of netdevs and driver private data in certain
    circumstances.

 4) Sanitize netlink message length properly in decnet, from Mateusz
    Jurczyk.

 5) Don't leak kernel data in rtnl_fill_vfinfo() netlink blobs. From
    Yuval Mintz.

 6) Hash secret is never initialized in ipv6 ILA translation code, from
    Arnd Bergmann. I guess those clang warnings about unused inline
    functions are useful for something!

 7) Fix endian selection in bpf_endian.h, from Daniel Borkmann.

 8) Sanitize sockaddr length before dereferncing any fields in AF_UNIX
    and CAIF. From Mateusz Jurczyk.

 9) Fix timestamping for GMAC3 chips in stmmac driver, from Mario
    Molitor.

10) Do not leak netdev on dev_alloc_name() errors in mac80211, from
    Johannes Berg.

11) Fix locking in sctp_for_each_endpoint(), from Xin Long.

12) Fix wrong memset size on 32-bit in snmp6, from Christian Perle.

13) Fix use after free in ip_mc_clear_src(), from WANG Cong.

14) Fix regressions caused by ICMP rate limiting changes in 4.11, from
    Jesper Dangaard Brouer.

* git://git.kernel.org/pub/scm/linux/kernel/git/davem/net: (91 commits)
  i40e: Fix a sleep-in-atomic bug
  net: don't global ICMP rate limit packets originating from loopback
  net/act_pedit: fix an error code
  net: update undefined ->ndo_change_mtu() comment
  net_sched: move tcf_lock down after gen_replace_estimator()
  caif: Add sockaddr length check before accessing sa_family in connect handler
  qed: fix dump of context data
  qmi_wwan: new Telewell and Sierra device IDs
  net: phy: Fix MDIO_THUNDER dependencies
  netconsole: Remove duplicate "netconsole: " logging prefix
  igmp: acquire pmc lock for ip_mc_clear_src()
  r8152: give the device version
  net: rps: fix uninitialized symbol warning
  mac80211: don't send SMPS action frame in AP mode when not needed
  mac80211/wpa: use constant time memory comparison for MACs
  mac80211: set bss_info data before configuring the channel
  mac80211: remove 5/10 MHz rate code from station MLME
  mac80211: Fix incorrect condition when checking rx timestamp
  mac80211: don't look at the PM bit of BAR frames
  i40e: fix handling of HW ATR eviction
  ...

Pull USB fixes from Greg KH:
 "Here are some small USB fixes for 4.12-rc5

  They are for some reported issues in the chipidea and gadget drivers.
  Nothing major. All have been in linux-next for a while with no
  reported issues"

* tag 'usb-4.12-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb:
  usb: gadget: udc: renesas_usb3: Fix PN_INT_ENA disabling timing
  usb: gadget: udc: renesas_usb3: lock for PN_ registers access
  usb: gadget: udc: renesas_usb3: fix deadlock by spinlock
  usb: gadget: udc: renesas_usb3: fix pm_runtime functions calling
  usb: gadget: f_mass_storage: Serialize wake and sleep execution
  usb: dwc2: add support for the DWC2 controller on Meson8 SoCs
  phy: qualcomm: phy-qcom-qmp: fix application of sizeof to pointer
  usb: musb: dsps: keep VBUS on for host-only mode
  usb: chipidea: core: check before accessing ci_role in ci_role_show
  usb: chipidea: debug: check before accessing ci_role
  phy: qcom-qmp: fix return value check in qcom_qmp_phy_create()
  usb: chipidea: udc: fix NULL pointer dereference if udc_start failed
  usb: chipidea: imx: Do not access CLKONOFF on i.MX51

Pull powerpc fixes from Michael Ellerman:
 "Mostly fairly minor, of note are:

   - Fix percpu allocations to be NUMA aware

   - Limit 4k page size config to 64TB virtual address space

   - Avoid needlessly restoring FP and vector registers

  Thanks to Aneesh Kumar K.V, Breno Leitao, Christophe Leroy, Frederic
  Barrat, Madhavan Srinivasan, Michael Bringmann, Nicholas Piggin,
  Vaibhav Jain"

* tag 'powerpc-4.12-5' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux:
  powerpc/book3s64: Move PPC_DT_CPU_FTRs and enable it by default
  powerpc/mm/4k: Limit 4k page size config to 64TB virtual address space
  cxl: Fix error path on bad ioctl
  powerpc/perf: Fix Power9 test_adder fields
  powerpc/numa: Fix percpu allocations to be NUMA aware
  cxl: Avoid double free_irq() for psl,slice interrupts
  powerpc/kernel: Initialize load_tm on task creation
  powerpc/kernel: Fix FP and vector register restoration
  powerpc/64: Reclaim CPU_FTR_SUBCORE
  powerpc/hotplug-mem: Fix missing endian conversion of aa_index
  powerpc/sysdev/simple_gpio: Fix oops in gpio save_regs function
  powerpc/spufs: Fix coredump of SPU contexts
  powerpc/64s: Add dt_cpu_ftrs boot time setup option

commit 61b905da33 ("net: Rename skb->rxhash to skb->hash")
didn't update the documentation, fix this up.

Cc: Tom Herbert <therbert@google.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Pull networking fixes from David Miller:

 1) Made TCP congestion control documentation match current reality,
    from Anmol Sarma.

 2) Various build warning and failure fixes from Arnd Bergmann.

 3) Fix SKB list leak in ipv6_gso_segment().

 4) Use after free in ravb driver, from Eugeniu Rosca.

 5) Don't use udp_poll() in ping protocol driver, from Eric Dumazet.

 6) Don't crash in PCI error recovery of cxgb4 driver, from Guilherme
    Piccoli.

 7) _SRC_NAT_DONE_BIT needs to be cleared using atomics, from Liping
    Zhang.

 8) Use after free in vxlan deletion, from Mark Bloch.

 9) Fix ordering of NAPI poll enabled in ethoc driver, from Max
    Filippov.

10) Fix stmmac hangs with TSO, from Niklas Cassel.

11) Fix crash in CALIPSO ipv6, from Richard Haines.

12) Clear nh_flags properly on mpls link up. From Roopa Prabhu.

13) Fix regression in sk_err socket error queue handling, noticed by
    ping applications. From Soheil Hassas Yeganeh.

14) Update mlx4/mlx5 MAINTAINERS information.

* git://git.kernel.org/pub/scm/linux/kernel/git/davem/net: (78 commits)
  net: stmmac: fix a broken u32 less than zero check
  net: stmmac: fix completely hung TX when using TSO
  net: ethoc: enable NAPI before poll may be scheduled
  net: bridge: fix a null pointer dereference in br_afspec
  ravb: Fix use-after-free on `ifconfig eth0 down`
  net/ipv6: Fix CALIPSO causing GPF with datagram support
  net: stmmac: ensure jumbo_frm error return is correctly checked for -ve value
  Revert "sit: reload iphdr in ipip6_rcv"
  i40e/i40evf: proper update of the page_offset field
  i40e: Fix state flags for bit set and clean operations of PF
  iwlwifi: fix host command memory leaks
  iwlwifi: fix min API version for 7265D, 3168, 8000 and 8265
  iwlwifi: mvm: clear new beacon command template struct
  iwlwifi: mvm: don't fail when removing a key from an inexisting sta
  iwlwifi: pcie: only use d0i3 in suspend/resume if system_pm is set to d0i3
  iwlwifi: mvm: fix firmware debug restart recording
  iwlwifi: tt: move ucode_loaded check under mutex
  iwlwifi: mvm: support ibss in dqa mode
  iwlwifi: mvm: Fix command queue number on d0i3 flow
  iwlwifi: mvm: rs: start using LQ command color
  ...

Update tcp.txt to fix mandatory congestion control ops and default
CCA selection. Also, fix comment in tcp.h for undo_cwnd.

Signed-off-by: Anmol Sarma <me@anmolsarma.in>
Signed-off-by: David S. Miller <davem@davemloft.net>

USB support in the Meson8 SoCs is provided by a DWC2 controller which
works with the same settings as Meson8b and GXBB. Using the generic
"snps,dwc2" binding results in an endless stream of "Overcurrent change
detected" messages.

Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

Provide a dt_cpu_ftrs= cmdline option to disable the dt_cpu_ftrs CPU
feature discovery, and fall back to the "cputable" based version.

Also allow control of advertising unknown features to userspace and
with this parameter, and remove the clunky CONFIG option.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
[mpe: Add explicit early check of bootargs in dt_cpu_ftrs_init()]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

Signed-off-by: Madalin Bucur <madalin.bucur@nxp.com>
Signed-off-by: Camelia Groza <camelia.groza@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>