linux/arch/arm
Hugh Dickins 1be7107fbe mm: larger stack guard gap, between vmas
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>
2017-06-19 21:50:20 +08:00
..
boot ARM: SoC fixes 2017-06-19 16:50:09 +08:00
common ARM: 8675/1: MCPM: ensure not to enter __hyp_soft_restart from loopback and cpu_power_down 2017-05-23 17:26:08 +01:00
configs ARM: configs: add a gemini defconfig 2017-05-18 23:56:47 -07:00
crypto crypto: arm/aes-neonbs - resolve fallback cipher at runtime 2017-03-09 18:34:16 +08:00
firmware
include IOMMU Fixes for Linux v4.12-rc4 2017-06-09 22:30:55 -07:00
kernel arm64 2nd set of updates for 4.12: 2017-05-11 11:27:54 -07:00
kvm arm: KVM: Allow unaligned accesses at HYP 2017-06-06 22:20:02 +02:00
lib new helper: uaccess_kernel() 2017-03-28 16:43:25 -04:00
mach-alpine ARM: 8641/1: treewide: Replace uses of virt_to_phys with __pa_symbol 2017-02-28 11:06:10 +00:00
mach-artpec ARM: ARTPEC-6: add select MFD_SYSCON to MACH_ARTPEC6 2016-11-26 00:06:34 +01:00
mach-asm9260
mach-aspeed ARM: aspeed: Select pinctrl drivers 2017-01-10 22:36:06 +11:00
mach-at91 Merge tag 'at91-4.12-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/abelloni/linux into fixes 2017-06-01 17:07:31 -07:00
mach-axxia ARM: 8641/1: treewide: Replace uses of virt_to_phys with __pa_symbol 2017-02-28 11:06:10 +00:00
mach-bcm ARM: remove duplicate 'const' annotations' 2017-05-19 10:12:55 +02:00
mach-berlin ARM: 8646/1: mmu: decouple VECTORS_BASE from Kconfig 2017-02-28 11:06:12 +00:00
mach-clps711x
mach-cns3xxx ARM: remove duplicate 'const' annotations' 2017-05-19 10:12:55 +02:00
mach-davinci ARM: davinci: PM: Do not free useful resources in normal path in 'davinci_pm_init' 2017-05-17 15:25:18 +05:30
mach-digicolor
mach-dove
mach-ebsa110
mach-efm32
mach-ep93xx ARM: ep93xx: Register ts73xx-fpga manager driver for TS-7300 2017-03-17 15:10:48 +09:00
mach-exynos Merge branch 'for-linus' of git://git.armlinux.org.uk/~rmk/linux-arm 2017-02-28 11:50:53 -08:00
mach-footbridge clocksource: Use a plain u64 instead of cycle_t 2016-12-25 11:04:12 +01:00
mach-gemini ARM: gemini: don't select SERIAL_OF_PLATFORM 2017-03-24 22:12:42 +01:00
mach-highbank
mach-hisi ARM: hisi: fix error return code in hip04_smp_init() 2017-03-28 15:30:54 +01:00
mach-imx ARM: SoC driver updates 2017-05-09 10:01:15 -07:00
mach-integrator ARM: SoC platform updates for v4.10 2016-12-15 15:39:02 -08:00
mach-iop13xx Replace <asm/uaccess.h> with <linux/uaccess.h> globally 2016-12-24 11:46:01 -08:00
mach-iop32x
mach-iop33x
mach-ixp4xx scripts/spelling.txt: add regsiter -> register spelling mistake 2017-05-08 17:15:13 -07:00
mach-keystone ARM: keystone: Drop PM domain support for k2g 2017-04-04 08:59:28 -07:00
mach-ks8695
mach-lpc18xx
mach-lpc32xx ARM: SoC platform updates for v4.10 2016-12-15 15:39:02 -08:00
mach-mediatek ARM: 8641/1: treewide: Replace uses of virt_to_phys with __pa_symbol 2017-02-28 11:06:10 +00:00
mach-meson
mach-mmp ARM: mmp: let clk_disable() return immediately if clk is NULL 2017-03-30 17:38:34 +02:00
mach-moxart irqchip/faraday: Replace moxa with ftintc010 2017-04-07 10:36:30 +01:00
mach-mv78xx0 ARM: mv78xx0: fix possible PCI buffer overflow 2017-01-27 17:52:57 +01:00
mach-mvebu Merge branch 'for-linus' of git://git.armlinux.org.uk/~rmk/linux-arm 2017-02-28 11:50:53 -08:00
mach-mxs ARM: mxs: add support for I2SE Duckbill 2 boards 2017-04-10 21:25:50 +08:00
mach-netx
mach-nomadik
mach-nspire
mach-omap1 ARM: OMAP: PM: Drop useless checks for PM_SUSPEND_STANDBY 2017-03-06 10:38:19 -08:00
mach-omap2 ARM: remove duplicate 'const' annotations' 2017-05-19 10:12:55 +02:00
mach-orion5x ARM: orion5x: only call into phylib when available 2017-03-30 17:30:39 +02:00
mach-oxnas ARM: oxnas: remove redundant select CPU_V6K 2017-03-20 10:13:45 +01:00
mach-picoxcell
mach-prima2 ARM: 8641/1: treewide: Replace uses of virt_to_phys with __pa_symbol 2017-02-28 11:06:10 +00:00
mach-pxa ARM: pxa/raumfeld: fix compile error in rotary controller resources 2017-04-18 11:28:38 -07:00
mach-qcom
mach-realview ARM: 8641/1: treewide: Replace uses of virt_to_phys with __pa_symbol 2017-02-28 11:06:10 +00:00
mach-rockchip Merge branch 'for-linus' of git://git.armlinux.org.uk/~rmk/linux-arm 2017-02-28 11:50:53 -08:00
mach-rpc sched/headers: Prepare for new header dependencies before moving code to <linux/sched/mm.h> 2017-03-02 08:42:28 +01:00
mach-s3c24xx Merge branch 'for-linus' of git://git.armlinux.org.uk/~rmk/linux-arm 2017-02-28 11:50:53 -08:00
mach-s3c64xx regulator: arizona-ldo1: Move pdata into a separate structure 2017-04-25 16:36:32 +01:00
mach-s5pv210 Merge branch 'for-linus' of git://git.armlinux.org.uk/~rmk/linux-arm 2017-02-28 11:50:53 -08:00
mach-sa1100 ARM: 8641/1: treewide: Replace uses of virt_to_phys with __pa_symbol 2017-02-28 11:06:10 +00:00
mach-shmobile ARM: 8660/1: shmobile: r7s72100: Enable L2 cache 2017-03-17 10:01:27 +00:00
mach-socfpga ARM: 8641/1: treewide: Replace uses of virt_to_phys with __pa_symbol 2017-02-28 11:06:10 +00:00
mach-spear ARM: remove duplicate 'const' annotations' 2017-05-19 10:12:55 +02:00
mach-sti ARM: 8641/1: treewide: Replace uses of virt_to_phys with __pa_symbol 2017-02-28 11:06:10 +00:00
mach-stm32 ARM: stm32: Add a new SOC - STM32H743 2017-03-24 11:37:24 +01:00
mach-sunxi ARM: sunxi: Select PM_OPP 2017-03-06 07:37:41 +01:00
mach-tango ARM: 8641/1: treewide: Replace uses of virt_to_phys with __pa_symbol 2017-02-28 11:06:10 +00:00
mach-tegra soc/tegra: Move Tegra flowctrl driver 2017-04-04 15:48:04 +02:00
mach-u300
mach-uniphier
mach-ux500 ARM: SoC: late DT updates for v4.11 2017-03-03 16:15:48 -08:00
mach-versatile
mach-vexpress ARM: 8641/1: treewide: Replace uses of virt_to_phys with __pa_symbol 2017-02-28 11:06:10 +00:00
mach-vt8500
mach-w90x900 ARM: w90x900: let clk_disable() return immediately if clk is NULL 2017-03-30 17:37:19 +02:00
mach-zx ARM: 8641/1: treewide: Replace uses of virt_to_phys with __pa_symbol 2017-02-28 11:06:10 +00:00
mach-zynq ARM: 8641/1: treewide: Replace uses of virt_to_phys with __pa_symbol 2017-02-28 11:06:10 +00:00
mm mm: larger stack guard gap, between vmas 2017-06-19 21:50:20 +08:00
net arm: use set_memory.h header 2017-05-08 17:15:13 -07:00
nwfpe sched/headers: Move task_struct::signal and task_struct::sighand types and accessors into <linux/sched/signal.h> 2017-03-03 01:43:37 +01:00
oprofile
plat-iop clocksource: Use a plain u64 instead of cycle_t 2016-12-25 11:04:12 +01:00
plat-omap
plat-orion ARM: orion5x: only call into phylib when available 2017-03-30 17:30:39 +02:00
plat-pxa
plat-samsung dmaengine: pl330: remove pdata based initialization 2017-03-28 21:37:48 +05:30
plat-versatile ARM: plat-versatile: remove stale clock header 2017-04-07 11:57:57 +02:00
probes arm: kprobes: Align stack to 8-bytes in test code 2017-03-21 16:24:19 +00:00
tools ARM: wire up statx syscall 2017-03-10 10:15:15 +00:00
vdso
vfp sched/headers: Prepare for new header dependencies before moving code to <linux/sched/signal.h> 2017-03-02 08:42:29 +01:00
xen xen: Implement EFI reset_system callback 2017-05-02 12:06:50 +02:00
Kconfig ARM: SoC platform updates 2017-05-09 09:49:36 -07:00
Kconfig-nommu ARM: 8635/1: nommu: allow enabling REMAP_VECTORS_TO_RAM 2017-01-10 23:32:54 +00:00
Kconfig.debug arch: Move CONFIG_DEBUG_RODATA and CONFIG_SET_MODULE_RONX to be common 2017-02-07 12:32:52 -08:00
Makefile arm: Use full path in KBUILD_IMAGE definition 2017-03-20 22:42:20 +09:00