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  1. 04 Oct, 2016 6 commits
    • Vegard Nossum's avatar
      ALSA: timer: fix division by zero after SNDRV_TIMER_IOCTL_CONTINUE · a987c625
      Vegard Nossum authored 
      [ Upstream commit 6b760bb2 ]

I got this:

    divide error: 0000 [#1] PREEMPT SMP KASAN
    CPU: 1 PID: 1327 Comm: a.out Not tainted 4.8.0-rc2+ #189
    Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.9.3-0-ge2fc41e-prebuilt.qemu-project.org 04/01/2014
    task: ffff8801120a9580 task.stack: ffff8801120b0000
    RIP: 0010:[<ffffffff82c8bd9a>]  [<ffffffff82c8bd9a>] snd_hrtimer_callback+0x1da/0x3f0
    RSP: 0018:ffff88011aa87da8  EFLAGS: 00010006
    RAX: 0000000000004f76 RBX: ffff880112655e88 RCX: 0000000000000000
    RDX: 0000000000000000 RSI: ffff880112655ea0 RDI: 0000000000000001
    RBP: ffff88011aa87e00 R08: ffff88013fff905c R09: ffff88013fff9048
    R10: ffff88013fff9050 R11: 00000001050a7b8c R12: ffff880114778a00
    R13: ffff880114778ab4 R14: ffff880114778b30 R15: 0000000000000000
    FS:  00007f071647c700(0000) GS:ffff88011aa80000(0000) knlGS:0000000000000000
    CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
    CR2: 0000000000603001 CR3: 0000000112021000 CR4: 00000000000006e0
    Stack:
     0000000000000000 ffff880114778ab8 ffff880112655ea0 0000000000004f76
     ffff880112655ec8 ffff880112655e80 ffff880112655e88 ffff88011aa98fc0
     00000000b97ccf2b dffffc0000000000 ffff88011aa98fc0 ffff88011aa87ef0
    Call Trace:
     <IRQ>
     [<ffffffff813abce7>] __hrtimer_run_queues+0x347/0xa00
     [<ffffffff82c8bbc0>] ? snd_hrtimer_close+0x130/0x130
     [<ffffffff813ab9a0>] ? retrigger_next_event+0x1b0/0x1b0
     [<ffffffff813ae1a6>] ? hrtimer_interrupt+0x136/0x4b0
     [<ffffffff813ae220>] hrtimer_interrupt+0x1b0/0x4b0
     [<ffffffff8120f91e>] local_apic_timer_interrupt+0x6e/0xf0
     [<ffffffff81227ad3>] ? kvm_guest_apic_eoi_write+0x13/0xc0
     [<ffffffff83c35086>] smp_apic_timer_interrupt+0x76/0xa0
     [<ffffffff83c3416c>] apic_timer_interrupt+0x8c/0xa0
     <EOI>
     [<ffffffff83c3239c>] ? _raw_spin_unlock_irqrestore+0x2c/0x60
     [<ffffffff82c8185d>] snd_timer_start1+0xdd/0x670
     [<ffffffff82c87015>] snd_timer_continue+0x45/0x80
     [<ffffffff82c88100>] snd_timer_user_ioctl+0x1030/0x2830
     [<ffffffff8159f3a0>] ? __follow_pte.isra.49+0x430/0x430
     [<ffffffff82c870d0>] ? snd_timer_pause+0x80/0x80
     [<ffffffff815a26fa>] ? do_wp_page+0x3aa/0x1c90
     [<ffffffff815aa4f8>] ? handle_mm_fault+0xbc8/0x27f0
     [<ffffffff815a9930>] ? __pmd_alloc+0x370/0x370
     [<ffffffff82c870d0>] ? snd_timer_pause+0x80/0x80
     [<ffffffff816b0733>] do_vfs_ioctl+0x193/0x1050
     [<ffffffff816b05a0>] ? ioctl_preallocate+0x200/0x200
     [<ffffffff81002f2f>] ? syscall_trace_enter+0x3cf/0xdb0
     [<ffffffff815045ba>] ? __context_tracking_exit.part.4+0x9a/0x1e0
     [<ffffffff81002b60>] ? exit_to_usermode_loop+0x190/0x190
     [<ffffffff82001a97>] ? check_preemption_disabled+0x37/0x1e0
     [<ffffffff81d93889>] ? security_file_ioctl+0x89/0xb0
     [<ffffffff816b167f>] SyS_ioctl+0x8f/0xc0
     [<ffffffff816b15f0>] ? do_vfs_ioctl+0x1050/0x1050
     [<ffffffff81005524>] do_syscall_64+0x1c4/0x4e0
     [<ffffffff83c32b2a>] entry_SYSCALL64_slow_path+0x25/0x25
    Code: e8 fc 42 7b fe 8b 0d 06 8a 50 03 49 0f af cf 48 85 c9 0f 88 7c 01 00 00 48 89 4d a8 e8 e0 42 7b fe 48 8b 45 c0 48 8b 4d a8 48 99 <48> f7 f9 49 01 c7 e8 cb 42 7b fe 48 8b 55 d0 48 b8 00 00 00 00
    RIP  [<ffffffff82c8bd9a>] snd_hrtimer_callback+0x1da/0x3f0
     RSP <ffff88011aa87da8>
    ---[ end trace 6aa380f756a21074 ]---

The problem happens when you call ioctl(SNDRV_TIMER_IOCTL_CONTINUE) on a
completely new/unused timer -- it will have ->sticks == 0, which causes a
divide by 0 in snd_hrtimer_callback().
Signed-off-by: default avatarVegard Nossum <vegard.nossum@oracle.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
Signed-off-by: default avatarSasha Levin <alexander.levin@verizon.com>
      a987c625
    • Simon Baatz's avatar
      ARM: kirkwood: ib62x0: fix size of u-boot environment partition · d0a2d410
      Simon Baatz authored 
      [ Upstream commit a7789378 ]

Commit 148c274e ("ARM: kirkwood: ib62x0: add u-boot environment
partition") split the "u-boot" partition into "u-boot" and "u-boot
environment".  However, instead of the size of the environment, an offset
was given, resulting in overlapping partitions.
Signed-off-by: default avatarSimon Baatz <gmbnomis@gmail.com>
Fixes: 148c274e ("ARM: kirkwood: ib62x0: add u-boot environment partition")
Cc: Jason Cooper <jason@lakedaemon.net>
Cc: Andrew Lunn <andrew@lunn.ch>
Cc: Gregory Clement <gregory.clement@free-electrons.com>
Cc: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
Cc: Luka Perkov <luka@openwrt.org>
Cc: stable@vger.kernel.org # 3.13+
Reviewed-by: default avatarAndrew Lunn <andrew@lunn.ch>
Signed-off-by: default avatarGregory CLEMENT <gregory.clement@free-electrons.com>
Signed-off-by: default avatarSasha Levin <alexander.levin@verizon.com>
      d0a2d410
    • Pawel Moll's avatar
      bus: arm-ccn: Fix XP watchpoint settings bitmask · cb366258
      Pawel Moll authored 
      [ Upstream commit b928466b ]

The code setting XP watchpoint comparator and mask registers should, in
order to be fully compliant with specification, zero one or more most
significant bits of each field. In both L cases it means zeroing bit 63.
The bitmask doing this was wrong, though, zeroing bit 60 instead.
Fortunately, due to a lucky coincidence, this turned out to be fairly
innocent with the existing hardware.

Fixed now.

Cc: stable@vger.kernel.org # 3.17+
Signed-off-by: default avatarPawel Moll <pawel.moll@arm.com>
Signed-off-by: default avatarSasha Levin <alexander.levin@verizon.com>
      cb366258
    • Pawel Moll's avatar
      bus: arm-ccn: Do not attempt to configure XPs for cycle counter · 703dd66f
      Pawel Moll authored 
      [ Upstream commit b7c1beb2 ]

Fuzzing the CCN perf driver revealed a small but definitely dangerous
mistake in the event setup code. When a cycle counter is requested, the
driver should not reconfigure the events bus at all, otherwise it will
corrupt (in most but the simplest cases) its configuration and may end
up accessing XP array out of its bounds and corrupting control
registers.
Reported-by: default avatarMark Rutland <mark.rutland@arm.com>
Reviewed-by: default avatarMark Rutland <mark.rutland@arm.com>
Tested-by: default avatarMark Rutland <mark.rutland@arm.com>
Cc: stable@vger.kernel.org # 3.17+
Signed-off-by: default avatarPawel Moll <pawel.moll@arm.com>
Signed-off-by: default avatarSasha Levin <alexander.levin@verizon.com>
      703dd66f
    • Johannes Berg's avatar
      Revert "wext: Fix 32 bit iwpriv compatibility issue with 64 bit Kernel" · 26a0e0c2
      Johannes Berg authored 
      [ Upstream commit 4d0bd46a ]

This reverts commit 3d5fdff4.

Ben Hutchings pointed out that the commit isn't safe since it assumes
that the structure used by the driver is iw_point, when in fact there's
no way to know about that.

Fortunately, the only driver in the tree that ever runs this code path
is the wilc1000 staging driver, so it doesn't really matter.

Clearly I should have investigated this better before applying, sorry.
Reported-by: default avatarBen Hutchings <ben@decadent.org.uk>
Cc: stable@vger.kernel.org [though I guess it doesn't matter much]
Fixes: 3d5fdff4 ("wext: Fix 32 bit iwpriv compatibility issue with 64 bit Kernel")
Signed-off-by: default avatarJohannes Berg <johannes.berg@intel.com>
Signed-off-by: default avatarSasha Levin <alexander.levin@verizon.com>
      26a0e0c2
    • Sebastian Reichel's avatar
      ARM: OMAP3: hwmod data: Add sysc information for DSI · 177b4898
      Sebastian Reichel authored 
      [ Upstream commit b46211d6 ]

Add missing sysconfig/sysstatus information
to OMAP3 hwmod. The information has been
checked against OMAP34xx and OMAP36xx TRM.

Without this change DSI block is not reset
during boot, which is required for working
Nokia N950 display.
Signed-off-by: default avatarSebastian Reichel <sre@kernel.org>
Cc: stable@vger.kernel.org
Signed-off-by: default avatarTony Lindgren <tony@atomide.com>
Signed-off-by: default avatarSasha Levin <alexander.levin@verizon.com>
      177b4898
  3. 22 Sep, 2016 1 commit
  5. 18 Sep, 2016 1 commit
    • James Hogan's avatar
      MIPS: KVM: Check for pfn noslot case · 7cc3f9b1
      James Hogan authored 
      commit ba913e4f upstream.

When mapping a page into the guest we error check using is_error_pfn(),
however this doesn't detect a value of KVM_PFN_NOSLOT, indicating an
error HVA for the page. This can only happen on MIPS right now due to
unusual memslot management (e.g. being moved / removed / resized), or
with an Enhanced Virtual Memory (EVA) configuration where the default
KVM_HVA_ERR_* and kvm_is_error_hva() definitions are unsuitable (fixed
in a later patch). This case will be treated as a pfn of zero, mapping
the first page of physical memory into the guest.

It would appear the MIPS KVM port wasn't updated prior to being merged
(in v3.10) to take commit 81c52c56 ("KVM: do not treat noslot pfn as
a error pfn") into account (merged v3.8), which converted a bunch of
is_error_pfn() calls to is_error_noslot_pfn(). Switch to using
is_error_noslot_pfn() instead to catch this case properly.

Fixes: 858dd5d4 ("KVM/MIPS32: MMU/TLB operations for the Guest.")
Signed-off-by: default avatarJames Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
[james.hogan@imgtec.com: Backport to v4.7.y]
Signed-off-by: default avatarJames Hogan <james.hogan@imgtec.com>
Signed-off-by: default avatarSasha Levin <alexander.levin@verizon.com>
      7cc3f9b1
  7. 17 Sep, 2016 1 commit
  9. 15 Sep, 2016 9 commits
    • Sasha Levin's avatar
      Revert "ARC: mm: don't loose PTE_SPECIAL in pte_modify()" · cac5e8f4
      Sasha Levin authored 
      This reverts commit 77c6ffdb.
Signed-off-by: default avatarSasha Levin <alexander.levin@verizon.com>
      cac5e8f4
    • Emanuel Czirai's avatar
      x86/AMD: Apply erratum 665 on machines without a BIOS fix · 7c17facc
      Emanuel Czirai authored 
      [ Upstream commit d1992996 ]

AMD F12h machines have an erratum which can cause DIV/IDIV to behave
unpredictably. The workaround is to set MSRC001_1029[31] but sometimes
there is no BIOS update containing that workaround so let's do it
ourselves unconditionally. It is simple enough.

[ Borislav: Wrote commit message. ]
Signed-off-by: default avatarEmanuel Czirai <icanrealizeum@gmail.com>
Signed-off-by: default avatarBorislav Petkov <bp@suse.de>
Cc: Yaowu Xu <yaowu@google.com>
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/20160902053550.18097-1-bp@alien8.deSigned-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarSasha Levin <alexander.levin@verizon.com>
      7c17facc
    • Steven Rostedt's avatar
      x86/paravirt: Do not trace _paravirt_ident_*() functions · 18ec3adc
      Steven Rostedt authored 
      [ Upstream commit 15301a57 ]

Łukasz Daniluk reported that on a RHEL kernel that his machine would lock up
after enabling function tracer. I asked him to bisect the functions within
available_filter_functions, which he did and it came down to three:

  _paravirt_nop(), _paravirt_ident_32() and _paravirt_ident_64()

It was found that this is only an issue when noreplace-paravirt is added
to the kernel command line.

This means that those functions are most likely called within critical
sections of the funtion tracer, and must not be traced.

In newer kenels _paravirt_nop() is defined within gcc asm(), and is no
longer an issue.  But both _paravirt_ident_{32,64}() causes the
following splat when they are traced:

 mm/pgtable-generic.c:33: bad pmd ffff8800d2435150(0000000001d00054)
 mm/pgtable-generic.c:33: bad pmd ffff8800d3624190(0000000001d00070)
 mm/pgtable-generic.c:33: bad pmd ffff8800d36a5110(0000000001d00054)
 mm/pgtable-generic.c:33: bad pmd ffff880118eb1450(0000000001d00054)
 NMI watchdog: BUG: soft lockup - CPU#2 stuck for 22s! [systemd-journal:469]
 Modules linked in: e1000e
 CPU: 2 PID: 469 Comm: systemd-journal Not tainted 4.6.0-rc4-test+ #513
 Hardware name: Hewlett-Packard HP Compaq Pro 6300 SFF/339A, BIOS K01 v02.05 05/07/2012
 task: ffff880118f740c0 ti: ffff8800d4aec000 task.ti: ffff8800d4aec000
 RIP: 0010:[<ffffffff81134148>]  [<ffffffff81134148>] queued_spin_lock_slowpath+0x118/0x1a0
 RSP: 0018:ffff8800d4aefb90  EFLAGS: 00000246
 RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffff88011eb16d40
 RDX: ffffffff82485760 RSI: 000000001f288820 RDI: ffffea0000008030
 RBP: ffff8800d4aefb90 R08: 00000000000c0000 R09: 0000000000000000
 R10: ffffffff821c8e0e R11: 0000000000000000 R12: ffff880000200fb8
 R13: 00007f7a4e3f7000 R14: ffffea000303f600 R15: ffff8800d4b562e0
 FS:  00007f7a4e3d7840(0000) GS:ffff88011eb00000(0000) knlGS:0000000000000000
 CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
 CR2: 00007f7a4e3f7000 CR3: 00000000d3e71000 CR4: 00000000001406e0
 Call Trace:
   _raw_spin_lock+0x27/0x30
   handle_pte_fault+0x13db/0x16b0
   handle_mm_fault+0x312/0x670
   __do_page_fault+0x1b1/0x4e0
   do_page_fault+0x22/0x30
   page_fault+0x28/0x30
   __vfs_read+0x28/0xe0
   vfs_read+0x86/0x130
   SyS_read+0x46/0xa0
   entry_SYSCALL_64_fastpath+0x1e/0xa8
 Code: 12 48 c1 ea 0c 83 e8 01 83 e2 30 48 98 48 81 c2 40 6d 01 00 48 03 14 c5 80 6a 5d 82 48 89 0a 8b 41 08 85 c0 75 09 f3 90 8b 41 08 <85> c0 74 f7 4c 8b 09 4d 85 c9 74 08 41 0f 18 09 eb 02 f3 90 8b
Reported-by: default avatarŁukasz Daniluk <lukasz.daniluk@intel.com>
Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
Cc: stable@vger.kernel.org
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: default avatarSasha Levin <alexander.levin@verizon.com>
      18ec3adc
    • Miklos Szeredi's avatar
      ovl: listxattr: use strnlen() · f4572434
      Miklos Szeredi authored 
      [ Upstream commit 7cb35119 ]

Be defensive about what underlying fs provides us in the returned xattr
list buffer.  If it's not properly null terminated, bail out with a warning
insead of BUG.
Signed-off-by: default avatarMiklos Szeredi <mszeredi@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarSasha Levin <alexander.levin@verizon.com>
      f4572434
    • Miklos Szeredi's avatar
      ovl: remove posix_acl_default from workdir · cc318bc6
      Miklos Szeredi authored 
      [ Upstream commit c11b9fdd ]

Clear out posix acl xattrs on workdir and also reset the mode after
creation so that an inherited sgid bit is cleared.
Signed-off-by: default avatarMiklos Szeredi <mszeredi@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarSasha Levin <alexander.levin@verizon.com>
      cc318bc6
    • Tejun Heo's avatar
      kernfs: don't depend on d_find_any_alias() when generating notifications · 0b764b2e
      Tejun Heo authored 
      [ Upstream commit df6a58c5 ]

kernfs_notify_workfn() sends out file modified events for the
scheduled kernfs_nodes.  Because the modifications aren't from
userland, it doesn't have the matching file struct at hand and can't
use fsnotify_modify().  Instead, it looked up the inode and then used
d_find_any_alias() to find the dentry and used fsnotify_parent() and
fsnotify() directly to generate notifications.

The assumption was that the relevant dentries would have been pinned
if there are listeners, which isn't true as inotify doesn't pin
dentries at all and watching the parent doesn't pin the child dentries
even for dnotify.  This led to, for example, inotify watchers not
getting notifications if the system is under memory pressure and the
matching dentries got reclaimed.  It can also be triggered through
/proc/sys/vm/drop_caches or a remount attempt which involves shrinking
dcache.

fsnotify_parent() only uses the dentry to access the parent inode,
which kernfs can do easily.  Update kernfs_notify_workfn() so that it
uses fsnotify() directly for both the parent and target inodes without
going through d_find_any_alias().  While at it, supply the target file
name to fsnotify() from kernfs_node->name.
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Reported-by: default avatarEvgeny Vereshchagin <evvers@ya.ru>
Fixes: d911d987 ("kernfs: make kernfs_notify() trigger inotify events too")
Cc: John McCutchan <john@johnmccutchan.com>
Cc: Robert Love <rlove@rlove.org>
Cc: Eric Paris <eparis@parisplace.org>
Cc: stable@vger.kernel.org # v3.16+
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: default avatarSasha Levin <alexander.levin@verizon.com>
      0b764b2e
    • Eric Biggers's avatar
      dm crypt: fix free of bad values after tfm allocation failure · 01d0c457
      Eric Biggers authored 
      [ Upstream commit 5d0be84e ]

If crypt_alloc_tfms() had to allocate multiple tfms and it failed before
the last allocation, then it would call crypt_free_tfms() and could free
pointers from uninitialized memory -- due to the crypt_free_tfms() check
for non-zero cc->tfms[i].  Fix by allocating zeroed memory.
Signed-off-by: default avatarEric Biggers <ebiggers@google.com>
Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: default avatarSasha Levin <alexander.levin@verizon.com>
      01d0c457
    • Mikulas Patocka's avatar
      dm crypt: fix error with too large bios · ab50c732
      Mikulas Patocka authored 
      [ Upstream commit 4e870e94 ]

When dm-crypt processes writes, it allocates a new bio in
crypt_alloc_buffer().  The bio is allocated from a bio set and it can
have at most BIO_MAX_PAGES vector entries, however the incoming bio can be
larger (e.g. if it was allocated by bcache).  If the incoming bio is
larger, bio_alloc_bioset() fails and an error is returned.

To avoid the error, we test for a too large bio in the function
crypt_map() and use dm_accept_partial_bio() to split the bio.
dm_accept_partial_bio() trims the current bio to the desired size and
asks DM core to send another bio with the rest of the data.
Signed-off-by: default avatarMikulas Patocka <mpatocka@redhat.com>
Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org # v3.16+
Signed-off-by: default avatarSasha Levin <alexander.levin@verizon.com>
      ab50c732
    • Trond Myklebust's avatar
      NFSv4.x: Fix a refcount leak in nfs_callback_up_net · 13312f0f
      Trond Myklebust authored 
      [ Upstream commit 98b0f80c ]

On error, the callers expect us to return without bumping
nn->cb_users[].
Signed-off-by: default avatarTrond Myklebust <trond.myklebust@primarydata.com>
Cc: stable@vger.kernel.org # v3.7+
Signed-off-by: default avatarSasha Levin <alexander.levin@verizon.com>
      13312f0f
  11. 13 Sep, 2016 3 commits
  13. 12 Sep, 2016 10 commits
  15. 11 Sep, 2016 1 commit
  17. 03 Sep, 2016 6 commits
  19. 02 Sep, 2016 1 commit
  21. 01 Sep, 2016 1 commit
    • Vegard Nossum's avatar
      fs/seq_file: fix out-of-bounds read · 5de0c13e
      Vegard Nossum authored 
      [ Upstream commit 088bf2ff ]

seq_read() is a nasty piece of work, not to mention buggy.

It has (I think) an old bug which allows unprivileged userspace to read
beyond the end of m->buf.

I was getting these:

    BUG: KASAN: slab-out-of-bounds in seq_read+0xcd2/0x1480 at addr ffff880116889880
    Read of size 2713 by task trinity-c2/1329
    CPU: 2 PID: 1329 Comm: trinity-c2 Not tainted 4.8.0-rc1+ #96
    Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.9.3-0-ge2fc41e-prebuilt.qemu-project.org 04/01/2014
    Call Trace:
      kasan_object_err+0x1c/0x80
      kasan_report_error+0x2cb/0x7e0
      kasan_report+0x4e/0x80
      check_memory_region+0x13e/0x1a0
      kasan_check_read+0x11/0x20
      seq_read+0xcd2/0x1480
      proc_reg_read+0x10b/0x260
      do_loop_readv_writev.part.5+0x140/0x2c0
      do_readv_writev+0x589/0x860
      vfs_readv+0x7b/0xd0
      do_readv+0xd8/0x2c0
      SyS_readv+0xb/0x10
      do_syscall_64+0x1b3/0x4b0
      entry_SYSCALL64_slow_path+0x25/0x25
    Object at ffff880116889100, in cache kmalloc-4096 size: 4096
    Allocated:
    PID = 1329
      save_stack_trace+0x26/0x80
      save_stack+0x46/0xd0
      kasan_kmalloc+0xad/0xe0
      __kmalloc+0x1aa/0x4a0
      seq_buf_alloc+0x35/0x40
      seq_read+0x7d8/0x1480
      proc_reg_read+0x10b/0x260
      do_loop_readv_writev.part.5+0x140/0x2c0
      do_readv_writev+0x589/0x860
      vfs_readv+0x7b/0xd0
      do_readv+0xd8/0x2c0
      SyS_readv+0xb/0x10
      do_syscall_64+0x1b3/0x4b0
      return_from_SYSCALL_64+0x0/0x6a
    Freed:
    PID = 0
    (stack is not available)
    Memory state around the buggy address:
     ffff88011688a000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
     ffff88011688a080: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
    >ffff88011688a100: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
		       ^
     ffff88011688a180: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
     ffff88011688a200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
    ==================================================================
    Disabling lock debugging due to kernel taint

This seems to be the same thing that Dave Jones was seeing here:

  https://lkml.org/lkml/2016/8/12/334

There are multiple issues here:

  1) If we enter the function with a non-empty buffer, there is an attempt
     to flush it. But it was not clearing m->from after doing so, which
     means that if we try to do this flush twice in a row without any call
     to traverse() in between, we are going to be reading from the wrong
     place -- the splat above, fixed by this patch.

  2) If there's a short write to userspace because of page faults, the
     buffer may already contain multiple lines (i.e. pos has advanced by
     more than 1), but we don't save the progress that was made so the
     next call will output what we've already returned previously. Since
     that is a much less serious issue (and I have a headache after
     staring at seq_read() for the past 8 hours), I'll leave that for now.

Link: http://lkml.kernel.org/r/1471447270-32093-1-git-send-email-vegard.nossum@oracle.comSigned-off-by: default avatarVegard Nossum <vegard.nossum@oracle.com>
Reported-by: default avatarDave Jones <davej@codemonkey.org.uk>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: default avatarSasha Levin <alexander.levin@verizon.com>
      5de0c13e
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