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[PATCH 4.9 06/88] net: unix: properly re-increment inflight counter of GC discarded candidates

From Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Newsgroups linux.kernel
Subject [PATCH 4.9 06/88] net: unix: properly re-increment inflight counter of GC discarded candidates
Date 2017-03-28 15:10 +0200
Message-ID <tpZ2N-83l-13@gated-at.bofh.it> (permalink)
References <tpYJs-7Cs-3@gated-at.bofh.it>
Organization linux.* mail to news gateway

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4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Andrey Ulanov <andreyu@google.com>


[ Upstream commit 7df9c24625b9981779afb8fcdbe2bb4765e61147 ]

Dmitry has reported that a BUG_ON() condition in unix_notinflight()
may be triggered by a simple code that forwards unix socket in an
SCM_RIGHTS message.
That is caused by incorrect unix socket GC implementation in unix_gc().

The GC first collects list of candidates, then (a) decrements their
"children's" inflight counter, (b) checks which inflight counters are
now 0, and then (c) increments all inflight counters back.
(a) and (c) are done by calling scan_children() with inc_inflight or
dec_inflight as the second argument.

Commit 6209344f5a37 ("net: unix: fix inflight counting bug in garbage
collector") changed scan_children() such that it no longer considers
sockets that do not have UNIX_GC_CANDIDATE flag. It also added a block
of code that that unsets this flag _before_ invoking
scan_children(, dec_iflight, ). This may lead to incorrect inflight
counters for some sockets.

This change fixes this bug by changing order of operations:
UNIX_GC_CANDIDATE is now unset only after all inflight counters are
restored to the original state.

  kernel BUG at net/unix/garbage.c:149!
  RIP: 0010:[<ffffffff8717ebf4>]  [<ffffffff8717ebf4>]
  unix_notinflight+0x3b4/0x490 net/unix/garbage.c:149
  Call Trace:
   [<ffffffff8716cfbf>] unix_detach_fds.isra.19+0xff/0x170 net/unix/af_unix.c:1487
   [<ffffffff8716f6a9>] unix_destruct_scm+0xf9/0x210 net/unix/af_unix.c:1496
   [<ffffffff86a90a01>] skb_release_head_state+0x101/0x200 net/core/skbuff.c:655
   [<ffffffff86a9808a>] skb_release_all+0x1a/0x60 net/core/skbuff.c:668
   [<ffffffff86a980ea>] __kfree_skb+0x1a/0x30 net/core/skbuff.c:684
   [<ffffffff86a98284>] kfree_skb+0x184/0x570 net/core/skbuff.c:705
   [<ffffffff871789d5>] unix_release_sock+0x5b5/0xbd0 net/unix/af_unix.c:559
   [<ffffffff87179039>] unix_release+0x49/0x90 net/unix/af_unix.c:836
   [<ffffffff86a694b2>] sock_release+0x92/0x1f0 net/socket.c:570
   [<ffffffff86a6962b>] sock_close+0x1b/0x20 net/socket.c:1017
   [<ffffffff81a76b8e>] __fput+0x34e/0x910 fs/file_table.c:208
   [<ffffffff81a771da>] ____fput+0x1a/0x20 fs/file_table.c:244
   [<ffffffff81483ab0>] task_work_run+0x1a0/0x280 kernel/task_work.c:116
   [<     inline     >] exit_task_work include/linux/task_work.h:21
   [<ffffffff8141287a>] do_exit+0x183a/0x2640 kernel/exit.c:828
   [<ffffffff8141383e>] do_group_exit+0x14e/0x420 kernel/exit.c:931
   [<ffffffff814429d3>] get_signal+0x663/0x1880 kernel/signal.c:2307
   [<ffffffff81239b45>] do_signal+0xc5/0x2190 arch/x86/kernel/signal.c:807
   [<ffffffff8100666a>] exit_to_usermode_loop+0x1ea/0x2d0
  arch/x86/entry/common.c:156
   [<     inline     >] prepare_exit_to_usermode arch/x86/entry/common.c:190
   [<ffffffff81009693>] syscall_return_slowpath+0x4d3/0x570
  arch/x86/entry/common.c:259
   [<ffffffff881478e6>] entry_SYSCALL_64_fastpath+0xc4/0xc6

Link: https://lkml.org/lkml/2017/3/6/252
Signed-off-by: Andrey Ulanov <andreyu@google.com>
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Fixes: 6209344 ("net: unix: fix inflight counting bug in garbage collector")
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/unix/garbage.c |   17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

--- a/net/unix/garbage.c
+++ b/net/unix/garbage.c
@@ -146,6 +146,7 @@ void unix_notinflight(struct user_struct
 	if (s) {
 		struct unix_sock *u = unix_sk(s);
 
+		BUG_ON(!atomic_long_read(&u->inflight));
 		BUG_ON(list_empty(&u->link));
 
 		if (atomic_long_dec_and_test(&u->inflight))
@@ -341,6 +342,14 @@ void unix_gc(void)
 	}
 	list_del(&cursor);
 
+	/* Now gc_candidates contains only garbage.  Restore original
+	 * inflight counters for these as well, and remove the skbuffs
+	 * which are creating the cycle(s).
+	 */
+	skb_queue_head_init(&hitlist);
+	list_for_each_entry(u, &gc_candidates, link)
+		scan_children(&u->sk, inc_inflight, &hitlist);
+
 	/* not_cycle_list contains those sockets which do not make up a
 	 * cycle.  Restore these to the inflight list.
 	 */
@@ -350,14 +359,6 @@ void unix_gc(void)
 		list_move_tail(&u->link, &gc_inflight_list);
 	}
 
-	/* Now gc_candidates contains only garbage.  Restore original
-	 * inflight counters for these as well, and remove the skbuffs
-	 * which are creating the cycle(s).
-	 */
-	skb_queue_head_init(&hitlist);
-	list_for_each_entry(u, &gc_candidates, link)
-	scan_children(&u->sk, inc_inflight, &hitlist);
-
 	spin_unlock(&unix_gc_lock);
 
 	/* Here we are. Hitlist is filled. Die. */

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[PATCH 4.9 00/88] 4.9.19-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 14:50 +0200
  [PATCH 4.9 23/88] Input: iforce - validate number of endpoints before using them Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 14:50 +0200
  [PATCH 4.9 21/88] Input: elan_i2c - add ASUS EeeBook X205TA special touchpad fw Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 14:50 +0200
  [PATCH 4.9 44/88] USB: usbtmc: add missing endpoint sanity check Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 14:50 +0200
  [PATCH 4.9 79/88] intel_th: Dont leak module refcount on failure to activate Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 14:50 +0200
  [PATCH 4.9 43/88] usb: hub: Fix crash after failure to read BOS descriptor Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 14:50 +0200
  [PATCH 4.9 67/88] xen/acpi: upload PM state from init-domain to Xen Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 14:50 +0200
  [PATCH 4.9 82/88] libceph: dont set weight to IN when OSD is destroyed Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 14:50 +0200
  [PATCH 4.9 22/88] Input: i8042 - add noloop quirk for Dell Embedded Box PC 3000 Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 14:50 +0200
  [PATCH 4.9 72/88] cpufreq: Restore policy min/max limits on CPU online Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 14:50 +0200
  [PATCH 4.9 24/88] Input: ims-pcu - validate number of endpoints before using them Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 14:50 +0200
  [PATCH 4.9 01/88] net/openvswitch: Set the ipv6 source tunnel key address attribute correctly Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 14:50 +0200
  [PATCH 4.9 47/88] uwb: hwa-rc: fix NULL-deref at probe Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 14:50 +0200
  [PATCH 4.9 50/88] iio: sw-device: Fix config group initialization Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 14:50 +0200
  [PATCH 4.9 17/88] socket, bpf: fix sk_filter use after free in sk_clone_lock Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 14:50 +0200
  [PATCH 4.9 41/88] USB: wusbcore: fix NULL-deref at probe Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 14:50 +0200
  [PATCH 4.9 42/88] usb: musb: cppi41: dont check early-TX-interrupt for Isoch transfer Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 14:50 +0200
  [PATCH 4.9 39/88] USB: lvtest: fix NULL-deref at probe Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 14:50 +0200
  [PATCH 4.9 56/88] powerpc/64s: Fix idle wakeup potential to clobber registers Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 14:50 +0200
  [PATCH 4.9 86/88] drm: reference count event->completion Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 14:50 +0200
  [PATCH 4.9 85/88] nl80211: fix dumpit error path RTNL deadlocks Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 14:50 +0200
  [PATCH 4.9 10/88] net/mlx5e: Use the proper UAPI values when offloading TC vlan actions Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 14:50 +0200
  [PATCH 4.9 31/88] ALSA: ctxfi: Fix the incorrect check of dma_set_mask() call Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 14:50 +0200
  [PATCH 4.9 53/88] parport: fix attempt to write duplicate procfiles Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 14:50 +0200
  [PATCH 4.9 32/88] ALSA: hda - Adding a group of pin definition to fix headset problem Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 14:50 +0200
  [PATCH 4.9 38/88] USB: uss720: fix NULL-deref at probe Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 14:50 +0200
  [PATCH 4.9 28/88] Input: kbtab - validate number of endpoints before using them Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 14:50 +0200
  [PATCH 4.9 81/88] Drivers: hv: vmbus: Dont leak memory when a channel is rescinded Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 14:50 +0200
  [PATCH 4.9 30/88] ALSA: seq: Fix racy cell insertions during snd_seq_pool_done() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 14:50 +0200
  [PATCH 4.9 88/88] crypto: algif_hash - avoid zero-sized array Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 14:50 +0200
  [PATCH 4.9 55/88] ext4: lock the xattr block before checksuming it Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 14:50 +0200
  [PATCH 4.9 61/88] hwrng: amd - Revert managed API changes Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 14:50 +0200
  [PATCH 4.9 83/88] device-dax: fix pmd/pte fault fallback handling Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 15:00 +0200
  [PATCH 4.9 45/88] USB: usbtmc: fix probe error path Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 15:00 +0200
  [PATCH 4.9 84/88] drm/bridge: analogix dp: Fix runtime PM state on driver bind Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 15:00 +0200
  [PATCH 4.9 62/88] hwrng: geode - Revert managed API changes Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 15:00 +0200
  [PATCH 4.9 87/88] fbcon: Fix vc attr at deinit Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 15:00 +0200
  [PATCH 4.9 66/88] crypto: ccp - Assign DMA commands to the channels CCP Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 15:00 +0200
  [PATCH 4.9 48/88] mmc: ushc: fix NULL-deref at probe Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 15:00 +0200
  [PATCH 4.9 46/88] uwb: i1480-dfu: fix NULL-deref at probe Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 15:00 +0200
  [PATCH 4.9 80/88] Drivers: hv: vmbus: Dont leak channel ids Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 15:00 +0200
  [PATCH 4.9 08/88] net: vrf: Reset rt6i_idev in local dst after put Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 15:10 +0200
  [PATCH 4.9 71/88] arm64: kaslr: Fix up the kernel image alignment Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 15:10 +0200
  [PATCH 4.9 06/88] net: unix: properly re-increment inflight counter of GC discarded candidates Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 15:10 +0200
  [PATCH 4.9 63/88] clk: sunxi-ng: sun6i: Fix enable bit offset for hdmi-ddc module clock Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 15:10 +0200
  [PATCH 4.9 59/88] mmc: sdhci: Do not disable interrupts while waiting for clock Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 15:10 +0200
  [PATCH 4.9 51/88] iio: hid-sensor-trigger: Change get poll value function order to avoid sensor properties losing after resume from S3 Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 15:10 +0200
  [PATCH 4.9 52/88] iio: magnetometer: ak8974: remove incorrect __exit markups Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 15:10 +0200
  [PATCH 4.9 05/88] openvswitch: Add missing case OVS_TUNNEL_KEY_ATTR_PAD Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 15:10 +0200
  [PATCH 4.9 78/88] jbd2: dont leak memory if setting up journal fails Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 15:10 +0200
  [PATCH 4.9 58/88] mmc: sdhci-of-arasan: fix incorrect timeout clock Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 15:10 +0200
  [PATCH 4.9 54/88] ext4: mark inode dirty after converting inline directory Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 15:10 +0200
  [PATCH 4.9 73/88] cgroup, net_cls: iterate the fds of only the tasks which are being migrated Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 15:10 +0200
  [PATCH 4.9 74/88] blk-mq: dont complete un-started request in timeout handler Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 15:10 +0200
  [PATCH 4.9 40/88] USB: idmouse: fix NULL-deref at probe Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 15:10 +0200
  [PATCH 4.9 64/88] clk: sunxi-ng: mp: Adjust parent rate for pre-dividers Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 15:10 +0200
  [PATCH 4.9 77/88] auxdisplay: img-ascii-lcd: add missing sentinel entry in img_ascii_lcd_matches Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 15:10 +0200
  [PATCH 4.9 76/88] drm/amdgpu: reinstate oland workaround for sclk Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 15:10 +0200
  [PATCH 4.9 09/88] net/mlx5: Add missing entries for set/query rate limit commands Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 15:10 +0200
  [PATCH 4.9 57/88] mmc: sdhci-of-at91: Support external regulators Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 15:10 +0200
  [PATCH 4.9 69/88] Revert "ARM: at91/dt: sama5d2: Use new compatible for ohci node" Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 15:10 +0200
  [PATCH 4.9 65/88] mwifiex: pcie: dont leak DMA buffers when removing Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 15:10 +0200
  [PATCH 4.9 68/88] iommu/vt-d: Fix NULL pointer dereference in device_to_iommu Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 15:10 +0200
  [PATCH 4.9 37/88] usb-core: Add LINEAR_FRAME_INTR_BINTERVAL USB quirk Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 15:10 +0200
  [PATCH 4.9 70/88] ARM: at91: pm: cpu_idle: switch DDR to power-down mode Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 15:10 +0200
  [PATCH 4.9 49/88] iio: adc: ti_am335x_adc: fix fifo overrun recovery Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 15:10 +0200
  [PATCH 4.9 75/88] libceph: force GFP_NOIO for socket allocations Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 15:10 +0200
    Re: [PATCH 4.9 75/88] libceph: force GFP_NOIO for socket allocations Michal Hocko <mhocko@kernel.org> - 2017-03-29 10:20 +0200
  [PATCH 4.9 14/88] ipv6: make sure to initialize sockc.tsflags before first use Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 15:20 +0200
  [PATCH 4.9 16/88] ipv4: provide stronger user input validation in nl_fib_input() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 15:20 +0200
  [PATCH 4.9 02/88] net: bcmgenet: Do not suspend PHY if Wake-on-LAN is enabled Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 15:20 +0200
  [PATCH 4.9 25/88] Input: hanwang - validate number of endpoints before using them Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 15:20 +0200
  [PATCH 4.9 15/88] net: bcmgenet: remove bcmgenet_internal_phy_setup() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 15:20 +0200
  [PATCH 4.9 04/88] amd-xgbe: Fix jumbo MTU processing on newer hardware Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 15:20 +0200
  [PATCH 4.9 36/88] usb: gadget: f_uvc: Fix SuperSpeed companion descriptors wBytesPerInterval Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 15:20 +0200
  [PATCH 4.9 29/88] Input: sur40 - validate number of endpoints before using them Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 15:20 +0200
  [PATCH 4.9 03/88] net: properly release sk_frag.page Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 15:20 +0200
  [PATCH 4.9 26/88] Input: yealink - validate number of endpoints before using them Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 15:20 +0200
  [PATCH 4.9 12/88] net/mlx5e: Count GSO packets correctly Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 15:20 +0200
  [PATCH 4.9 13/88] net/mlx5e: Count LRO packets correctly Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 15:20 +0200
  [PATCH 4.9 33/88] USB: serial: option: add Quectel UC15, UC20, EC21, and EC25 modems Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 15:20 +0200
  [PATCH 4.9 20/88] Input: ALPS - fix trackstick button handling on V8 devices Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 15:20 +0200
  [PATCH 4.9 18/88] tcp: initialize icsk_ack.lrcvtime at session start time Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 15:20 +0200
  [PATCH 4.9 19/88] Input: ALPS - fix V8+ protocol handling (73 03 28) Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 15:20 +0200
  [PATCH 4.9 11/88] net/mlx5: Increase number of max QPs in default profile Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-28 15:20 +0200
  Re: [PATCH 4.9 00/88] 4.9.19-stable review Shuah Khan <shuahkh@osg.samsung.com> - 2017-03-28 21:50 +0200
  Re: [PATCH 4.9 00/88] 4.9.19-stable review Guenter Roeck <linux@roeck-us.net> - 2017-03-29 06:50 +0200
  Re: [PATCH 4.9 00/88] 4.9.19-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-29 07:50 +0200

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