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From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-kernel@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	stable@vger.kernel.org, Eric Dumazet <edumazet@google.com>,
	"David S. Miller" <davem@davemloft.net>
Subject: [PATCH 4.14 42/62] net: add skb_queue_empty_lockless()
Date: Fri,  8 Nov 2019 19:50:30 +0100
Message-ID: <20191108174749.326432373@linuxfoundation.org> (raw)
In-Reply-To: <20191108174719.228826381@linuxfoundation.org>

From: Eric Dumazet <edumazet@google.com>

[ Upstream commit d7d16a89350ab263484c0aa2b523dd3a234e4a80 ]

Some paths call skb_queue_empty() without holding
the queue lock. We must use a barrier in order
to not let the compiler do strange things, and avoid
KCSAN splats.

Adding a barrier in skb_queue_empty() might be overkill,
I prefer adding a new helper to clearly identify
points where the callers might be lockless. This might
help us finding real bugs.

The corresponding WRITE_ONCE() should add zero cost
for current compilers.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 include/linux/skbuff.h |   33 ++++++++++++++++++++++++---------
 1 file changed, 24 insertions(+), 9 deletions(-)

--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -1346,6 +1346,19 @@ static inline int skb_queue_empty(const
 }
 
 /**
+ *	skb_queue_empty_lockless - check if a queue is empty
+ *	@list: queue head
+ *
+ *	Returns true if the queue is empty, false otherwise.
+ *	This variant can be used in lockless contexts.
+ */
+static inline bool skb_queue_empty_lockless(const struct sk_buff_head *list)
+{
+	return READ_ONCE(list->next) == (const struct sk_buff *) list;
+}
+
+
+/**
  *	skb_queue_is_last - check if skb is the last entry in the queue
  *	@list: queue head
  *	@skb: buffer
@@ -1709,9 +1722,11 @@ static inline void __skb_insert(struct s
 				struct sk_buff *prev, struct sk_buff *next,
 				struct sk_buff_head *list)
 {
-	newsk->next = next;
-	newsk->prev = prev;
-	next->prev  = prev->next = newsk;
+	/* see skb_queue_empty_lockless() for the opposite READ_ONCE() */
+	WRITE_ONCE(newsk->next, next);
+	WRITE_ONCE(newsk->prev, prev);
+	WRITE_ONCE(next->prev, newsk);
+	WRITE_ONCE(prev->next, newsk);
 	list->qlen++;
 }
 
@@ -1722,11 +1737,11 @@ static inline void __skb_queue_splice(co
 	struct sk_buff *first = list->next;
 	struct sk_buff *last = list->prev;
 
-	first->prev = prev;
-	prev->next = first;
+	WRITE_ONCE(first->prev, prev);
+	WRITE_ONCE(prev->next, first);
 
-	last->next = next;
-	next->prev = last;
+	WRITE_ONCE(last->next, next);
+	WRITE_ONCE(next->prev, last);
 }
 
 /**
@@ -1867,8 +1882,8 @@ static inline void __skb_unlink(struct s
 	next	   = skb->next;
 	prev	   = skb->prev;
 	skb->next  = skb->prev = NULL;
-	next->prev = prev;
-	prev->next = next;
+	WRITE_ONCE(next->prev, prev);
+	WRITE_ONCE(prev->next, next);
 }
 
 /**



  parent reply index

Thread overview: 66+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-08 18:49 [PATCH 4.14 00/62] 4.14.153-stable review Greg Kroah-Hartman
2019-11-08 18:49 ` [PATCH 4.14 01/62] arm64: dts: Fix gpio to pinmux mapping Greg Kroah-Hartman
2019-11-08 18:49 ` [PATCH 4.14 02/62] regulator: ti-abb: Fix timeout in ti_abb_wait_txdone/ti_abb_clear_all_txdone Greg Kroah-Hartman
2019-11-08 18:49 ` [PATCH 4.14 03/62] regulator: pfuze100-regulator: Variable "val" in pfuze100_regulator_probe() could be uninitialized Greg Kroah-Hartman
2019-11-08 18:49 ` [PATCH 4.14 04/62] ASoC: wm_adsp: Dont generate kcontrols without READ flags Greg Kroah-Hartman
2019-11-08 18:49 ` [PATCH 4.14 05/62] ASoc: rockchip: i2s: Fix RPM imbalance Greg Kroah-Hartman
2019-11-08 18:49 ` [PATCH 4.14 06/62] ARM: dts: logicpd-torpedo-som: Remove twl_keypad Greg Kroah-Hartman
2019-11-08 18:49 ` [PATCH 4.14 07/62] pinctrl: ns2: Fix off by one bugs in ns2_pinmux_enable() Greg Kroah-Hartman
2019-11-08 18:49 ` [PATCH 4.14 08/62] ARM: mm: fix alignment handler faults under memory pressure Greg Kroah-Hartman
2019-11-08 18:49 ` [PATCH 4.14 09/62] scsi: scsi_dh_alua: handle RTPG sense code correctly during state transitions Greg Kroah-Hartman
2019-11-08 18:49 ` [PATCH 4.14 10/62] scsi: sni_53c710: fix compilation error Greg Kroah-Hartman
2019-11-08 18:49 ` [PATCH 4.14 11/62] scsi: fix kconfig dependency warning related to 53C700_LE_ON_BE Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.14 12/62] ARM: dts: imx7s: Correct GPTs ipg clock source Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.14 13/62] perf c2c: Fix memory leak in build_cl_output() Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.14 14/62] perf kmem: Fix memory leak in compact_gfp_flags() Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.14 15/62] ARM: davinci: dm365: Fix McBSP dma_slave_map entry Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.14 16/62] scsi: target: core: Do not overwrite CDB byte 1 Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.14 17/62] ARM: 8926/1: v7m: remove register save to stack before svc Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.14 18/62] of: unittest: fix memory leak in unittest_data_add Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.14 19/62] MIPS: bmips: mark exception vectors as char arrays Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.14 20/62] i2c: stm32f7: remove warning when compiling with W=1 Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.14 21/62] cifs: Fix cifsInodeInfo lock_sem deadlock when reconnect occurs Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.14 22/62] nbd: handle racing with errored out commands Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.14 23/62] cxgb4: fix panic when attaching to ULD fail Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.14 24/62] dccp: do not leak jiffies on the wire Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.14 25/62] net: annotate accesses to sk->sk_incoming_cpu Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.14 26/62] net: annotate lockless accesses to sk->sk_napi_id Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.14 27/62] net: dsa: bcm_sf2: Fix IMP setup for port different than 8 Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.14 28/62] net: ethernet: ftgmac100: Fix DMA coherency issue with SW checksum Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.14 29/62] net: fix sk_page_frag() recursion from memory reclaim Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.14 30/62] net: hisilicon: Fix ping latency when deal with high throughput Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.14 31/62] net/mlx4_core: Dynamically set guaranteed amount of counters per VF Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.14 32/62] net: Zeroing the structure ethtool_wolinfo in ethtool_get_wol() Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.14 33/62] selftests: net: reuseport_dualstack: fix uninitalized parameter Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.14 34/62] udp: fix data-race in udp_set_dev_scratch() Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.14 35/62] net: add READ_ONCE() annotation in __skb_wait_for_more_packets() Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.14 36/62] net/mlx5e: Fix handling of compressed CQEs in case of low NAPI budget Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.14 37/62] net: dsa: b53: Do not clear existing mirrored port mask Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.14 38/62] net: usb: lan78xx: Connect PHY before registering MAC Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.14 39/62] r8152: add device id for Lenovo ThinkPad USB-C Dock Gen 2 Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.14 40/62] net: dsa: fix switch tree list Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.14 41/62] net: bcmgenet: reset 40nm EPHY on energy detect Greg Kroah-Hartman
2019-11-08 18:50 ` Greg Kroah-Hartman [this message]
2019-11-08 18:50 ` [PATCH 4.14 43/62] udp: use skb_queue_empty_lockless() Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.14 44/62] net: use skb_queue_empty_lockless() in poll() handlers Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.14 45/62] net: use skb_queue_empty_lockless() in busy poll contexts Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.14 46/62] vxlan: check tun_info options_len properly Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.14 47/62] erspan: fix the tun_info options_len check for erspan Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.14 48/62] inet: stop leaking jiffies on the wire Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.14 49/62] net/flow_dissector: switch to siphash Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.14 50/62] dmaengine: qcom: bam_dma: Fix resource leak Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.14 51/62] sched/wake_q: Fix wakeup ordering for wake_q Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.14 52/62] kbuild: use -fmacro-prefix-map to make __FILE__ a relative path Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.14 53/62] kbuild: add -fcf-protection=none when using retpoline flags Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.14 54/62] platform/x86: pmc_atom: Add Siemens SIMATIC IPC227E to critclk_systems DMI table Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.14 55/62] iio: adc: stm32-adc: move registers definitions Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.14 56/62] iio: adc: stm32-adc: fix a race when using several adcs with dma and irq Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.14 57/62] powerpc/mm: Fixup tlbie vs store ordering issue on POWER9 Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.14 58/62] powerpc/book3s64/mm: Dont do tlbie fixup for some hardware revisions Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.14 59/62] powerpc/book3s64/radix: Rename CPU_FTR_P9_TLBIE_BUG feature flag Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.14 60/62] powerpc/mm: Fixup tlbie vs mtpidr/mtlpidr ordering issue on POWER9 Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.14 61/62] selftests/powerpc: Add test case for tlbie vs mtpidr ordering issue Greg Kroah-Hartman
2019-11-08 18:50 ` [PATCH 4.14 62/62] selftests/powerpc: Fix compile error on tlbie_test due to newer gcc Greg Kroah-Hartman
2019-11-09  1:57 ` [PATCH 4.14 00/62] 4.14.153-stable review kernelci.org bot
2019-11-09 10:19 ` Naresh Kamboju
2019-11-09 15:40 ` Guenter Roeck

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