linux-stable.git/Documentation/kernel-parameters.txt, branch v3.18.76

mm: larger stack guard gap, between vmas

2017-06-26T05:10:54+00:00

commit 1be7107fbe18eed3e319a6c3e83c78254b693acb upstream.

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 
Original-patch-by: Michal Hocko 
Signed-off-by: Hugh Dickins 
Acked-by: Michal Hocko 
Tested-by: Helge Deller  # parisc
Signed-off-by: Linus Torvalds 
[wt: backport to 4.11: adjust context]
[wt: backport to 4.9: adjust context ; kernel doc was not in admin-guide]
[wt: backport to 4.4: adjust context ; drop ppc hugetlb_radix changes]
[wt: backport to 3.18: adjust context ; no FOLL_POPULATE ;
     s390 uses generic arch_get_unmapped_area()]
Signed-off-by: Willy Tarreau 
[gkh: minor build fixes for 3.18]
Signed-off-by: Greg Kroah-Hartman

USB: uas: Add a new NO_REPORT_LUNS quirk

2016-04-20T13:41:07+00:00

[ Upstream commit 1363074667a6b7d0507527742ccd7bbed5e3ceaa ]

Add a new NO_REPORT_LUNS quirk and set it for Seagate drives with
an usb-id of: 0bc2:331a, as these will fail to respond to a
REPORT_LUNS command.

Cc: stable@vger.kernel.org
Reported-and-tested-by: David Webb 
Signed-off-by: Hans de Goede 
Acked-by: Alan Stern 
Signed-off-by: Greg Kroah-Hartman 
Signed-off-by: Sasha Levin

uas: Add US_FL_MAX_SECTORS_240 flag

2015-05-17T23:12:40+00:00

[ Upstream commit ee136af4a064c2f61e2025873584d2c7ec93f4ae ]

The usb-storage driver sets max_sectors = 240 in its scsi-host template,
for uas we do not want to do that for all devices, but testing has shown
that some devices need it.

This commit adds a US_FL_MAX_SECTORS_240 flag for such devices, and
implements support for it in uas.c, while at it it also adds support
for US_FL_MAX_SECTORS_64 to uas.c.

Cc: stable@vger.kernel.org # 3.16
Signed-off-by: Hans de Goede 
Acked-by: Alan Stern 
Signed-off-by: Greg Kroah-Hartman 
Signed-off-by: Sasha Levin

Input: i8042 - reset keyboard to fix Elantech touchpad detection

2015-01-27T16:29:43+00:00

commit 148e9a711e034e06310a8c36b64957934ebe30f2 upstream.

On some laptops, keyboard needs to be reset in order to successfully detect
touchpad (e.g., some Gigabyte laptop models with Elantech touchpads).
Without resettin keyboard touchpad pretends to be completely dead.

Based on the original patch by Mateusz Jończyk this version has been
expanded to include DMI based detection & application of the fix
automatically on the affected models of laptops. This has been confirmed to
fix problem by three users already on three different models of laptops.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=81331
Signed-off-by: Srihari Vijayaraghavan 
Acked-by: Mateusz Jończyk 
Tested-by: Srihari Vijayaraghavan 
Tested by: Zakariya Dehlawi 
Tested-by: Guillaum Bouchard 
Signed-off-by: Dmitry Torokhov 
Signed-off-by: Greg Kroah-Hartman

USB: Update default usb-storage delay_use value in kernel-parameters.txt

2014-11-07T16:54:53+00:00

Back in 2010 the default usb-storage delay_use time was reduced from 5 to 1
second (commit a4a47bc03fe520e95e0c4212bf97c86545fb14f9), but
kernel-parameters.txt wasn't updated to reflect that.

Signed-off-by: Mark Knibbs 
Signed-off-by: Greg Kroah-Hartman

Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/dtor/input

2014-11-01T02:51:11+00:00

Pull input updates from Dmitry Torokhov:
 "A bunch of fixes for minor defects reported by Coverity, a few driver
  fixups and revert of i8042.nomux change so that we are once again
  enable active MUX mode if box claims to support it"

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/dtor/input:
  Revert "Input: i8042 - disable active multiplexing by default"
  Input: altera_ps2 - use correct type for irq return value
  Input: altera_ps2 - write to correct register when disabling interrupts
  Input: max77693-haptic - fix potential overflow
  Input: psmouse - remove unneeded check in psmouse_reconnect()
  Input: vsxxxaa - fix code dropping bytes from queue
  Input: ims-pcu - fix dead code in ims_pcu_ofn_reg_addr_store()
  Input: opencores-kbd - fix error handling
  Input: wm97xx - adapt parameters to tosa touchscreen.
  Input: i8042 - quirks for Fujitsu Lifebook A544 and Lifebook AH544
  Input: stmpe-keypad - fix valid key line bitmask
  Input: soc_button_array - update calls to gpiod_get*()

Merge tag 'docs-for-linus' of git://git.lwn.net/linux-2.6

2014-10-31T18:55:40+00:00

Pull documentation fixes from Jonathan Corbet:
 "So this is my first pull request since I rashly agreed to look after
  the documentation subtree.  It contains some typo fixes, a few minor
  documentation improvements, and, most importantly, fixes for a couple
  of build problems in various bits of sample code.

  I fully intend to start sending pull requests with signed tags.
  However, due to poor planning on my part and the general obnoxiousness
  of life, I'm 2000 miles away from my private key which is sitting on a
  powered-down machine.  This should be fixed before my next request.

  Meanwhile git.lwn.net is a machine under my control, the patches are
  all trivial, and all have done time in linux-next"

* tag 'docs-for-linus' of git://git.lwn.net/linux-2.6:
  Documentation/SubmittingPatches: Reported-by tags and permission
  Documentation: remove outdated references to the linux-next wiki
  Documentation: Restrict TSC test code to x86
  doc: kernel-parameters.txt: Add ide-generic.probe-mask
  vdso: don't require 64-bit math in standalone test
  Documentation: Add CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF case
  Documentation: Add default kmemleak off case in kernel-parameters.txt
  Docs: Document that the sticky bit is understood by hugetlbfs
  DocBook: Reduce noise from make cleandocs
  Documentation: fix vdso_standalone_test_x86 on 32-bit
  Documentation: dt-bindings: Explain order in patch series
  Documentation/ABI/testing/sysfs-ibft: fix a typo

Revert "Input: i8042 - disable active multiplexing by default"

2014-10-31T16:35:53+00:00

This reverts commit 68da166491655bc54051bf04c78ce648e2e33508.

It turns out that the assertion about scope of regressions due to
always keeping keyboard controller in legacy mode was proven wrong.
There are laptops, such as Clevo W650SH, that only have internal
touchpad (no external PS/2 ports), that require active multiplexing
mode to switch the touchpad (Elantech) into native mode instead of
basic PS/2 emulation.

Reported-by: Roel Aaij 
Signed-off-by: Dmitry Torokhov

doc: kernel-parameters.txt: Add ide-generic.probe-mask

2014-10-27T13:50:34+00:00

Signed-off-by: Maciej W. Rozycki 
[ jc: wording tweaked slightly ]
Signed-off-by: Jonathan Corbet

Documentation: Add default kmemleak off case in kernel-parameters.txt

2014-10-24T17:57:52+00:00

Add missing explanation about CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y case.

Signed-off-by: Masanari Iida 
Acked-by: Catalin Marinas 
Signed-off-by: Jonathan Corbet