Commit Graph

3678 Commits

Author SHA1 Message Date
Huang, Tao
ef179e79e9 Merge branch 'linux-linaro-lsk-v4.4-android' of git://git.linaro.org/kernel/linux-linaro-stable.git
* linux-linaro-lsk-v4.4-android: (61 commits)
  Linux 4.4.36
  scsi: mpt3sas: Unblock device after controller reset
  flow_dissect: call init_default_flow_dissectors() earlier
  mei: fix return value on disconnection
  mei: me: fix place for kaby point device ids.
  mei: me: disable driver on SPT SPS firmware
  drm/radeon: Ensure vblank interrupt is enabled on DPMS transition to on
  mpi: Fix NULL ptr dereference in mpi_powm() [ver #3]
  parisc: Also flush data TLB in flush_icache_page_asm
  parisc: Fix race in pci-dma.c
  parisc: Fix races in parisc_setup_cache_timing()
  NFSv4.x: hide array-bounds warning
  apparmor: fix change_hat not finding hat after policy replacement
  cfg80211: limit scan results cache size
  tile: avoid using clocksource_cyc2ns with absolute cycle count
  scsi: mpt3sas: Fix secure erase premature termination
  Fix USB CB/CBI storage devices with CONFIG_VMAP_STACK=y
  USB: serial: ftdi_sio: add support for TI CC3200 LaunchPad
  USB: serial: cp210x: add ID for the Zone DPMX
  usb: chipidea: move the lock initialization to core file
  ...
2016-12-06 20:58:56 +08:00
Alex Shi
bdcf7d8df4 Merge branch 'linux-linaro-lsk-v4.4' into linux-linaro-lsk-v4.4-android
Conflicts:
	keep low scan freq in android in net/wireless/scan.c
2016-12-06 13:01:29 +08:00
Alex Shi
3ba1692e72 Merge tag 'v4.4.36' into linux-linaro-lsk-v4.4
This is the 4.4.36 stable release
2016-12-05 12:01:22 +08:00
Huang, Tao
45cd824a30 Merge branch 'linux-linaro-lsk-v4.4-android' of git://git.linaro.org/kernel/linux-linaro-stable.git
* linux-linaro-lsk-v4.4-android: (315 commits)
  Linux 4.4.35
  netfilter: nft_dynset: fix element timeout for HZ != 1000
  IB/cm: Mark stale CM id's whenever the mad agent was unregistered
  IB/uverbs: Fix leak of XRC target QPs
  IB/core: Avoid unsigned int overflow in sg_alloc_table
  IB/mlx5: Fix fatal error dispatching
  IB/mlx5: Use cache line size to select CQE stride
  IB/mlx4: Fix create CQ error flow
  IB/mlx4: Check gid_index return value
  PM / sleep: don't suspend parent when async child suspend_{noirq, late} fails
  PM / sleep: fix device reference leak in test_suspend
  uwb: fix device reference leaks
  mfd: core: Fix device reference leak in mfd_clone_cell
  iwlwifi: pcie: fix SPLC structure parsing
  rtc: omap: Fix selecting external osc
  clk: mmp: mmp2: fix return value check in mmp2_clk_init()
  clk: mmp: pxa168: fix return value check in pxa168_clk_init()
  clk: mmp: pxa910: fix return value check in pxa910_clk_init()
  drm/amdgpu: Attach exclusive fence to prime exported bo's. (v5)
  crypto: caam - do not register AES-XTS mode on LP units
  ...

Change-Id: Ic14c01a22a5e8a0356d6c0ef6bcca7bc6cad6b4b
2016-12-02 20:31:31 +08:00
Andrey Ryabinin
2490908309 mpi: Fix NULL ptr dereference in mpi_powm() [ver #3]
commit f5527fffff3f002b0a6b376163613b82f69de073 upstream.

This fixes CVE-2016-8650.

If mpi_powm() is given a zero exponent, it wants to immediately return
either 1 or 0, depending on the modulus.  However, if the result was
initalised with zero limb space, no limbs space is allocated and a
NULL-pointer exception ensues.

Fix this by allocating a minimal amount of limb space for the result when
the 0-exponent case when the result is 1 and not touching the limb space
when the result is 0.

This affects the use of RSA keys and X.509 certificates that carry them.

BUG: unable to handle kernel NULL pointer dereference at           (null)
IP: [<ffffffff8138ce5d>] mpi_powm+0x32/0x7e6
PGD 0
Oops: 0002 [#1] SMP
Modules linked in:
CPU: 3 PID: 3014 Comm: keyctl Not tainted 4.9.0-rc6-fscache+ #278
Hardware name: ASUS All Series/H97-PLUS, BIOS 2306 10/09/2014
task: ffff8804011944c0 task.stack: ffff880401294000
RIP: 0010:[<ffffffff8138ce5d>]  [<ffffffff8138ce5d>] mpi_powm+0x32/0x7e6
RSP: 0018:ffff880401297ad8  EFLAGS: 00010212
RAX: 0000000000000000 RBX: ffff88040868bec0 RCX: ffff88040868bba0
RDX: ffff88040868b260 RSI: ffff88040868bec0 RDI: ffff88040868bee0
RBP: ffff880401297ba8 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000047 R11: ffffffff8183b210 R12: 0000000000000000
R13: ffff8804087c7600 R14: 000000000000001f R15: ffff880401297c50
FS:  00007f7a7918c700(0000) GS:ffff88041fb80000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 0000000401250000 CR4: 00000000001406e0
Stack:
 ffff88040868bec0 0000000000000020 ffff880401297b00 ffffffff81376cd4
 0000000000000100 ffff880401297b10 ffffffff81376d12 ffff880401297b30
 ffffffff81376f37 0000000000000100 0000000000000000 ffff880401297ba8
Call Trace:
 [<ffffffff81376cd4>] ? __sg_page_iter_next+0x43/0x66
 [<ffffffff81376d12>] ? sg_miter_get_next_page+0x1b/0x5d
 [<ffffffff81376f37>] ? sg_miter_next+0x17/0xbd
 [<ffffffff8138ba3a>] ? mpi_read_raw_from_sgl+0xf2/0x146
 [<ffffffff8132a95c>] rsa_verify+0x9d/0xee
 [<ffffffff8132acca>] ? pkcs1pad_sg_set_buf+0x2e/0xbb
 [<ffffffff8132af40>] pkcs1pad_verify+0xc0/0xe1
 [<ffffffff8133cb5e>] public_key_verify_signature+0x1b0/0x228
 [<ffffffff8133d974>] x509_check_for_self_signed+0xa1/0xc4
 [<ffffffff8133cdde>] x509_cert_parse+0x167/0x1a1
 [<ffffffff8133d609>] x509_key_preparse+0x21/0x1a1
 [<ffffffff8133c3d7>] asymmetric_key_preparse+0x34/0x61
 [<ffffffff812fc9f3>] key_create_or_update+0x145/0x399
 [<ffffffff812fe227>] SyS_add_key+0x154/0x19e
 [<ffffffff81001c2b>] do_syscall_64+0x80/0x191
 [<ffffffff816825e4>] entry_SYSCALL64_slow_path+0x25/0x25
Code: 56 41 55 41 54 53 48 81 ec a8 00 00 00 44 8b 71 04 8b 42 04 4c 8b 67 18 45 85 f6 89 45 80 0f 84 b4 06 00 00 85 c0 75 2f 41 ff ce <49> c7 04 24 01 00 00 00 b0 01 75 0b 48 8b 41 18 48 83 38 01 0f
RIP  [<ffffffff8138ce5d>] mpi_powm+0x32/0x7e6
 RSP <ffff880401297ad8>
CR2: 0000000000000000
---[ end trace d82015255d4a5d8d ]---

Basically, this is a backport of a libgcrypt patch:

	http://git.gnupg.org/cgi-bin/gitweb.cgi?p=libgcrypt.git;a=patch;h=6e1adb05d290aeeb1c230c763970695f4a538526

Fixes: cdec9cb516 ("crypto: GnuPG based MPI lib - source files (part 1)")
Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Dmitry Kasatkin <dmitry.kasatkin@gmail.com>
cc: linux-ima-devel@lists.sourceforge.net
Signed-off-by: James Morris <james.l.morris@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2016-12-02 09:09:01 +01:00
Alex Shi
068e31608a Merge branch 'linux-linaro-lsk-v4.4' into linux-linaro-lsk-v4.4-android
Conflicts:
	drivers/usb/gadget/function/u_ether.c
2016-11-25 12:55:17 +08:00
Alex Shi
5497d2d7d5 Merge remote-tracking branch 'lts/linux-4.4.y' into linux-linaro-lsk-v4.4
Conflicts:
	keep check_object_size in copy_from_user
	in arch/sparc/include/asm/uaccess_64.h
2016-11-25 12:50:56 +08:00
Daniel Mentz
ba8580f6cf lib/genalloc.c: start search from start of chunk
commit 62e931fac45b17c2a42549389879411572f75804 upstream.

gen_pool_alloc_algo() iterates over the chunks of a pool trying to find
a contiguous block of memory that satisfies the allocation request.

The shortcut

	if (size > atomic_read(&chunk->avail))
		continue;

makes the loop skip over chunks that do not have enough bytes left to
fulfill the request.  There are two situations, though, where an
allocation might still fail:

(1) The available memory is not contiguous, i.e.  the request cannot
    be fulfilled due to external fragmentation.

(2) A race condition.  Another thread runs the same code concurrently
    and is quicker to grab the available memory.

In those situations, the loop calls pool->algo() to search the entire
chunk, and pool->algo() returns some value that is >= end_bit to
indicate that the search failed.  This return value is then assigned to
start_bit.  The variables start_bit and end_bit describe the range that
should be searched, and this range should be reset for every chunk that
is searched.  Today, the code fails to reset start_bit to 0.  As a
result, prefixes of subsequent chunks are ignored.  Memory allocations
might fail even though there is plenty of room left in these prefixes of
those other chunks.

Fixes: 7f184275aa ("lib, Make gen_pool memory allocator lockless")
Link: http://lkml.kernel.org/r/1477420604-28918-1-git-send-email-danielmentz@google.com
Signed-off-by: Daniel Mentz <danielmentz@google.com>
Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2016-11-18 10:48:36 +01:00
Huang, Tao
f9ae5d202b Merge branch 'linux-linaro-lsk-v4.4-android' of git://git.linaro.org/kernel/linux-linaro-stable.git
* linux-linaro-lsk-v4.4-android: (1362 commits)
  Linux 4.4.30
  Revert "fix minor infoleak in get_user_ex()"
  Revert "x86/mm: Expand the exception table logic to allow new handling options"
  Linux 4.4.29
  ARM: pxa: pxa_cplds: fix interrupt handling
  powerpc/nvram: Fix an incorrect partition merge
  mpt3sas: Don't spam logs if logging level is 0
  perf symbols: Fixup symbol sizes before picking best ones
  perf symbols: Check symbol_conf.allow_aliases for kallsyms loading too
  perf hists browser: Fix event group display
  clk: divider: Fix clk_divider_round_rate() to use clk_readl()
  clk: qoriq: fix a register offset error
  s390/con3270: fix insufficient space padding
  s390/con3270: fix use of uninitialised data
  s390/cio: fix accidental interrupt enabling during resume
  x86/mm: Expand the exception table logic to allow new handling options
  dmaengine: ipu: remove bogus NO_IRQ reference
  power: bq24257: Fix use of uninitialized pointer bq->charger
  staging: r8188eu: Fix scheduling while atomic splat
  ASoC: dapm: Fix kcontrol creation for output driver widget
  ...
2016-11-04 14:30:24 +08:00
Alex Shi
c11a255c62 Merge branch 'linux-linaro-lsk-v4.4' into linux-linaro-lsk-v4.4-android 2016-10-29 13:26:04 +08:00
Alex Shi
25f89e269f Merge tag 'v4.4.28' into linux-linaro-lsk-v4.4
This is the 4.4.28 stable release
2016-10-29 13:26:01 +08:00
Kees Cook
75bd91f51e lib: add "on"/"off" support to kstrtobool
commit a81a5a17d44b26521fb1199f8ccf27f4af337a67 upstream.

Add support for "on" and "off" when converting to boolean.

Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: Amitkumar Karwar <akarwar@marvell.com>
Cc: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Joe Perches <joe@perches.com>
Cc: Kalle Valo <kvalo@codeaurora.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nishant Sarmukadam <nishants@marvell.com>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Steve French <sfrench@samba.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2016-10-28 03:01:31 -04:00
Kees Cook
e0d61779d3 lib: move strtobool() to kstrtobool()
commit ef951599074ba4fad2d0efa0a977129b41e6d203 upstream.

Create the kstrtobool_from_user() helper and move strtobool() logic into
the new kstrtobool() (matching all the other kstrto* functions).
Provides an inline wrapper for existing strtobool() callers.

Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: Joe Perches <joe@perches.com>
Cc: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Amitkumar Karwar <akarwar@marvell.com>
Cc: Nishant Sarmukadam <nishants@marvell.com>
Cc: Kalle Valo <kvalo@codeaurora.org>
Cc: Steve French <sfrench@samba.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2016-10-28 03:01:30 -04:00
Mark Rutland
824e71d68a BACKPORT: lib: harden strncpy_from_user
The strncpy_from_user() accessor is effectively a copy_from_user()
specialised to copy strings, terminating early at a NUL byte if possible.
In other respects it is identical, and can be used to copy an arbitrarily
large buffer from userspace into the kernel.  Conceptually, it exposes a
similar attack surface.

As with copy_from_user(), we check the destination range when the kernel
is built with KASAN, but unlike copy_from_user() we do not check the
destination buffer when using HARDENED_USERCOPY.  As strncpy_from_user()
calls get_user() in a loop, we must call check_object_size() explicitly.

This patch adds this instrumentation to strncpy_from_user(), per the same
rationale as with the regular copy_from_user().  In the absence of
hardened usercopy this will have no impact as the instrumentation expands
to an empty static inline function.

Link: http://lkml.kernel.org/r/1472221903-31181-1-git-send-email-mark.rutland@arm.com
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Kees Cook <keescook@chromium.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Bug: 31374226
Change-Id: I898e4e9f19307e37a9be497cb1a0d7f1e3911661
(cherry picked from commit bf90e56e467ed5766722972d483e6711889ed1b0)
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
2016-10-25 21:50:52 +08:00
Alex Shi
16d185eee4 Merge branch 'linux-linaro-lsk-v4.4' into linux-linaro-lsk-v4.4-android
Conflicts:
	kernel/cpuset.c
2016-10-11 23:33:37 +02:00
Alex Shi
10fd238c91 Merge remote-tracking branch 'lts/linux-4.4.y' into linux-linaro-lsk-v4.4
Conflicts:
	resovle the conflict on pax_copy for
	arch/ia64/include/asm/uaccess.h
	arch/powerpc/include/asm/uaccess.h
	arch/sparc/include/asm/uaccess_32.h
2016-10-05 13:21:50 +02:00
Alex Shi
daa56e80f3 Merge branch 'v4.4/topic/mm-kaslr-pax_usercopy' into linux-linaro-lsk-v4.4 2016-09-24 18:14:12 +08:00
Al Viro
99526912c9 fix iov_iter_fault_in_readable()
commit d4690f1e1cdabb4d61207b6787b1605a0dc0aeab upstream.

... by turning it into what used to be multipages counterpart

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2016-09-24 10:07:43 +02:00
Linus Torvalds
ed67fb82b1 unsafe_[get|put]_user: change interface to use a error target label
When I initially added the unsafe_[get|put]_user() helpers in commit
5b24a7a2aa20 ("Add 'unsafe' user access functions for batched
accesses"), I made the mistake of modeling the interface on our
traditional __[get|put]_user() functions, which return zero on success,
or -EFAULT on failure.

That interface is fairly easy to use, but it's actually fairly nasty for
good code generation, since it essentially forces the caller to check
the error value for each access.

In particular, since the error handling is already internally
implemented with an exception handler, and we already use "asm goto" for
various other things, we could fairly easily make the error cases just
jump directly to an error label instead, and avoid the need for explicit
checking after each operation.

So switch the interface to pass in an error label, rather than checking
the error value in the caller.  Best do it now before we start growing
more users (the signal handling code in particular would be a good place
to use the new interface).

So rather than

	if (unsafe_get_user(x, ptr))
		... handle error ..

the interface is now

	unsafe_get_user(x, ptr, label);

where an error during the user mode fetch will now just cause a jump to
'label' in the caller.

Right now the actual _implementation_ of this all still ends up being a
"if (err) goto label", and does not take advantage of any exception
label tricks, but for "unsafe_put_user()" in particular it should be
fairly straightforward to convert to using the exception table model.

Note that "unsafe_get_user()" is much harder to convert to a clever
exception table model, because current versions of gcc do not allow the
use of "asm goto" (for the exception) with output values (for the actual
value to be fetched).  But that is hopefully not a limitation in the
long term.

[ Also note that it might be a good idea to switch unsafe_get_user() to
  actually _return_ the value it fetches from user space, but this
  commit only changes the error handling semantics ]

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
(cherry picked from commit 1bd4403d86a1c06cb6cc9ac87664a0c9d3413d51)
Signed-off-by: Alex Shi <alex.shi@linaro.org>
2016-09-24 11:41:26 +08:00
Alex Shi
5f87c475f8 Merge branch 'linux-linaro-lsk-v4.4' into linux-linaro-lsk-v4.4-android
Conflicts:
	in fs/proc/task_mmu.c:
	looks like vma_get_anon_name() want have a name for anonymous
	vma when there is no name used in vma. commit: 586278d78b
	The name show is after any other names, so it maybe covered.
	but anyway, it just a show here.
2016-09-20 15:18:54 +08:00
Alex Shi
d2d693d1ba Merge remote-tracking branch 'lts/linux-4.4.y' into linux-linaro-lsk-v4.4
Conflicts:
	set ARM64_WORKAROUND_CAVIUM_27456 to 12 in
	arch/arm64/include/asm/cpufeature.h
	and add asm/memory.h in arch/arm64/kernel/entry.S
2016-09-20 10:17:00 +08:00
Nicolai Stange
11c27e850d lib/mpi: mpi_write_sgl(): fix skipping of leading zero limbs
commit f2d1362ff7d266b3d2b1c764d6c2ef4a3b457f23 upstream.

Currently, if the number of leading zeros is greater than fits into a
complete limb, mpi_write_sgl() skips them by iterating over them limb-wise.

However, it fails to adjust its internal leading zeros tracking variable,
lzeros, accordingly: it does a

  p -= sizeof(alimb);
  continue;

which should really have been a

  lzeros -= sizeof(alimb);
  continue;

Since lzeros never decreases if its initial value >= sizeof(alimb), nothing
gets copied by mpi_write_sgl() in that case.

Instead of skipping the high order zero limbs within the loop as shown
above, fix the issue by adjusting the copying loop's bounds.

Fixes: 2d4d1eea54 ("lib/mpi: Add mpi sgl helpers")
Signed-off-by: Nicolai Stange <nicstange@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2016-09-15 08:27:54 +02:00
David Howells
5afbd223e6 KEYS: Fix ASN.1 indefinite length object parsing
[ Upstream commit 23c8a812dc3c621009e4f0e5342aa4e2ede1ceaa ]

This fixes CVE-2016-0758.

In the ASN.1 decoder, when the length field of an ASN.1 value is extracted,
it isn't validated against the remaining amount of data before being added
to the cursor.  With a sufficiently large size indicated, the check:

	datalen - dp < 2

may then fail due to integer overflow.

Fix this by checking the length indicated against the amount of remaining
data in both places a definite length is determined.

Whilst we're at it, make the following changes:

 (1) Check the maximum size of extended length does not exceed the capacity
     of the variable it's being stored in (len) rather than the type that
     variable is assumed to be (size_t).

 (2) Compare the EOC tag to the symbolic constant ASN1_EOC rather than the
     integer 0.

 (3) To reduce confusion, move the initialisation of len outside of:

	for (len = 0; n > 0; n--) {

     since it doesn't have anything to do with the loop counter n.

Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
Acked-by: David Woodhouse <David.Woodhouse@intel.com>
Acked-by: Peter Jones <pjones@redhat.com>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2016-09-15 08:27:50 +02:00
Matt Wagantall
6c6dc1632a sched/rt: Add Kconfig option to enable panicking for RT throttling
This may be useful for detecting and debugging RT throttling issues.

Change-Id: I5807a897d11997d76421c1fcaa2918aad988c6c9
Signed-off-by: Matt Wagantall <mattw@codeaurora.org>
[rameezmustafa@codeaurora.org]: Port to msm-3.18]
Signed-off-by: Syed Rameez Mustafa <rameezmustafa@codeaurora.org>
[jstultz: forwardported to 4.4]
Signed-off-by: John Stultz <john.stultz@linaro.org>
2016-09-14 15:02:22 +05:30
Linus Torvalds
1cbefb3fb1 UPSTREAM: unsafe_[get|put]_user: change interface to use a error target label
When I initially added the unsafe_[get|put]_user() helpers in commit
5b24a7a2aa20 ("Add 'unsafe' user access functions for batched
accesses"), I made the mistake of modeling the interface on our
traditional __[get|put]_user() functions, which return zero on success,
or -EFAULT on failure.

That interface is fairly easy to use, but it's actually fairly nasty for
good code generation, since it essentially forces the caller to check
the error value for each access.

In particular, since the error handling is already internally
implemented with an exception handler, and we already use "asm goto" for
various other things, we could fairly easily make the error cases just
jump directly to an error label instead, and avoid the need for explicit
checking after each operation.

So switch the interface to pass in an error label, rather than checking
the error value in the caller.  Best do it now before we start growing
more users (the signal handling code in particular would be a good place
to use the new interface).

So rather than

	if (unsafe_get_user(x, ptr))
		... handle error ..

the interface is now

	unsafe_get_user(x, ptr, label);

where an error during the user mode fetch will now just cause a jump to
'label' in the caller.

Right now the actual _implementation_ of this all still ends up being a
"if (err) goto label", and does not take advantage of any exception
label tricks, but for "unsafe_put_user()" in particular it should be
fairly straightforward to convert to using the exception table model.

Note that "unsafe_get_user()" is much harder to convert to a clever
exception table model, because current versions of gcc do not allow the
use of "asm goto" (for the exception) with output values (for the actual
value to be fetched).  But that is hopefully not a limitation in the
long term.

[ Also note that it might be a good idea to switch unsafe_get_user() to
  actually _return_ the value it fetches from user space, but this
  commit only changes the error handling semantics ]

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Change-Id: Ib905a84a04d46984320f6fd1056da4d72f3d6b53
(cherry picked from commit 1bd4403d86a1c06cb6cc9ac87664a0c9d3413d51)
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
2016-09-14 14:43:17 +05:30