linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
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>,
	Dmitry Vyukov <dvyukov@google.com>,
	David Ahern <dsa@cumulusnetworks.com>,
	David Ahern <dsahern@gmail.com>,
	"David S. Miller" <davem@davemloft.net>
Subject: [PATCH 4.4 01/53] af_key: do not use GFP_KERNEL in atomic contexts
Date: Mon, 28 Aug 2017 10:05:06 +0200	[thread overview]
Message-ID: <20170828080517.671416691@linuxfoundation.org> (raw)
In-Reply-To: <20170828080517.599193891@linuxfoundation.org>

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

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

From: Eric Dumazet <edumazet@google.com>


[ Upstream commit 36f41f8fc6d8aa9f8c9072d66ff7cf9055f5e69b ]

pfkey_broadcast() might be called from non process contexts,
we can not use GFP_KERNEL in these cases [1].

This patch partially reverts commit ba51b6be38c1 ("net: Fix RCU splat in
af_key"), only keeping the GFP_ATOMIC forcing under rcu_read_lock()
section.

[1] : syzkaller reported :

in_atomic(): 1, irqs_disabled(): 0, pid: 2932, name: syzkaller183439
3 locks held by syzkaller183439/2932:
 #0:  (&net->xfrm.xfrm_cfg_mutex){+.+.+.}, at: [<ffffffff83b43888>] pfkey_sendmsg+0x4c8/0x9f0 net/key/af_key.c:3649
 #1:  (&pfk->dump_lock){+.+.+.}, at: [<ffffffff83b467f6>] pfkey_do_dump+0x76/0x3f0 net/key/af_key.c:293
 #2:  (&(&net->xfrm.xfrm_policy_lock)->rlock){+...+.}, at: [<ffffffff83957632>] spin_lock_bh include/linux/spinlock.h:304 [inline]
 #2:  (&(&net->xfrm.xfrm_policy_lock)->rlock){+...+.}, at: [<ffffffff83957632>] xfrm_policy_walk+0x192/0xa30 net/xfrm/xfrm_policy.c:1028
CPU: 0 PID: 2932 Comm: syzkaller183439 Not tainted 4.13.0-rc4+ #24
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:16 [inline]
 dump_stack+0x194/0x257 lib/dump_stack.c:52
 ___might_sleep+0x2b2/0x470 kernel/sched/core.c:5994
 __might_sleep+0x95/0x190 kernel/sched/core.c:5947
 slab_pre_alloc_hook mm/slab.h:416 [inline]
 slab_alloc mm/slab.c:3383 [inline]
 kmem_cache_alloc+0x24b/0x6e0 mm/slab.c:3559
 skb_clone+0x1a0/0x400 net/core/skbuff.c:1037
 pfkey_broadcast_one+0x4b2/0x6f0 net/key/af_key.c:207
 pfkey_broadcast+0x4ba/0x770 net/key/af_key.c:281
 dump_sp+0x3d6/0x500 net/key/af_key.c:2685
 xfrm_policy_walk+0x2f1/0xa30 net/xfrm/xfrm_policy.c:1042
 pfkey_dump_sp+0x42/0x50 net/key/af_key.c:2695
 pfkey_do_dump+0xaa/0x3f0 net/key/af_key.c:299
 pfkey_spddump+0x1a0/0x210 net/key/af_key.c:2722
 pfkey_process+0x606/0x710 net/key/af_key.c:2814
 pfkey_sendmsg+0x4d6/0x9f0 net/key/af_key.c:3650
sock_sendmsg_nosec net/socket.c:633 [inline]
 sock_sendmsg+0xca/0x110 net/socket.c:643
 ___sys_sendmsg+0x755/0x890 net/socket.c:2035
 __sys_sendmsg+0xe5/0x210 net/socket.c:2069
 SYSC_sendmsg net/socket.c:2080 [inline]
 SyS_sendmsg+0x2d/0x50 net/socket.c:2076
 entry_SYSCALL_64_fastpath+0x1f/0xbe
RIP: 0033:0x445d79
RSP: 002b:00007f32447c1dc8 EFLAGS: 00000202 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 0000000000445d79
RDX: 0000000000000000 RSI: 000000002023dfc8 RDI: 0000000000000008
RBP: 0000000000000086 R08: 00007f32447c2700 R09: 00007f32447c2700
R10: 00007f32447c2700 R11: 0000000000000202 R12: 0000000000000000
R13: 00007ffe33edec4f R14: 00007f32447c29c0 R15: 0000000000000000

Fixes: ba51b6be38c1 ("net: Fix RCU splat in af_key")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Cc: David Ahern <dsa@cumulusnetworks.com>
Acked-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/key/af_key.c |   48 ++++++++++++++++++++++++++----------------------
 1 file changed, 26 insertions(+), 22 deletions(-)

--- a/net/key/af_key.c
+++ b/net/key/af_key.c
@@ -228,7 +228,7 @@ static int pfkey_broadcast_one(struct sk
 #define BROADCAST_ONE		1
 #define BROADCAST_REGISTERED	2
 #define BROADCAST_PROMISC_ONLY	4
-static int pfkey_broadcast(struct sk_buff *skb,
+static int pfkey_broadcast(struct sk_buff *skb, gfp_t allocation,
 			   int broadcast_flags, struct sock *one_sk,
 			   struct net *net)
 {
@@ -278,7 +278,7 @@ static int pfkey_broadcast(struct sk_buf
 	rcu_read_unlock();
 
 	if (one_sk != NULL)
-		err = pfkey_broadcast_one(skb, &skb2, GFP_KERNEL, one_sk);
+		err = pfkey_broadcast_one(skb, &skb2, allocation, one_sk);
 
 	kfree_skb(skb2);
 	kfree_skb(skb);
@@ -311,7 +311,7 @@ static int pfkey_do_dump(struct pfkey_so
 		hdr = (struct sadb_msg *) pfk->dump.skb->data;
 		hdr->sadb_msg_seq = 0;
 		hdr->sadb_msg_errno = rc;
-		pfkey_broadcast(pfk->dump.skb, BROADCAST_ONE,
+		pfkey_broadcast(pfk->dump.skb, GFP_ATOMIC, BROADCAST_ONE,
 				&pfk->sk, sock_net(&pfk->sk));
 		pfk->dump.skb = NULL;
 	}
@@ -355,7 +355,7 @@ static int pfkey_error(const struct sadb
 	hdr->sadb_msg_len = (sizeof(struct sadb_msg) /
 			     sizeof(uint64_t));
 
-	pfkey_broadcast(skb, BROADCAST_ONE, sk, sock_net(sk));
+	pfkey_broadcast(skb, GFP_KERNEL, BROADCAST_ONE, sk, sock_net(sk));
 
 	return 0;
 }
@@ -1396,7 +1396,7 @@ static int pfkey_getspi(struct sock *sk,
 
 	xfrm_state_put(x);
 
-	pfkey_broadcast(resp_skb, BROADCAST_ONE, sk, net);
+	pfkey_broadcast(resp_skb, GFP_KERNEL, BROADCAST_ONE, sk, net);
 
 	return 0;
 }
@@ -1483,7 +1483,7 @@ static int key_notify_sa(struct xfrm_sta
 	hdr->sadb_msg_seq = c->seq;
 	hdr->sadb_msg_pid = c->portid;
 
-	pfkey_broadcast(skb, BROADCAST_ALL, NULL, xs_net(x));
+	pfkey_broadcast(skb, GFP_ATOMIC, BROADCAST_ALL, NULL, xs_net(x));
 
 	return 0;
 }
@@ -1596,7 +1596,7 @@ static int pfkey_get(struct sock *sk, st
 	out_hdr->sadb_msg_reserved = 0;
 	out_hdr->sadb_msg_seq = hdr->sadb_msg_seq;
 	out_hdr->sadb_msg_pid = hdr->sadb_msg_pid;
-	pfkey_broadcast(out_skb, BROADCAST_ONE, sk, sock_net(sk));
+	pfkey_broadcast(out_skb, GFP_ATOMIC, BROADCAST_ONE, sk, sock_net(sk));
 
 	return 0;
 }
@@ -1701,8 +1701,8 @@ static int pfkey_register(struct sock *s
 		return -ENOBUFS;
 	}
 
-	pfkey_broadcast(supp_skb, BROADCAST_REGISTERED, sk, sock_net(sk));
-
+	pfkey_broadcast(supp_skb, GFP_KERNEL, BROADCAST_REGISTERED, sk,
+			sock_net(sk));
 	return 0;
 }
 
@@ -1720,7 +1720,8 @@ static int unicast_flush_resp(struct soc
 	hdr->sadb_msg_errno = (uint8_t) 0;
 	hdr->sadb_msg_len = (sizeof(struct sadb_msg) / sizeof(uint64_t));
 
-	return pfkey_broadcast(skb, BROADCAST_ONE, sk, sock_net(sk));
+	return pfkey_broadcast(skb, GFP_ATOMIC, BROADCAST_ONE, sk,
+			       sock_net(sk));
 }
 
 static int key_notify_sa_flush(const struct km_event *c)
@@ -1741,7 +1742,7 @@ static int key_notify_sa_flush(const str
 	hdr->sadb_msg_len = (sizeof(struct sadb_msg) / sizeof(uint64_t));
 	hdr->sadb_msg_reserved = 0;
 
-	pfkey_broadcast(skb, BROADCAST_ALL, NULL, c->net);
+	pfkey_broadcast(skb, GFP_ATOMIC, BROADCAST_ALL, NULL, c->net);
 
 	return 0;
 }
@@ -1798,7 +1799,7 @@ static int dump_sa(struct xfrm_state *x,
 	out_hdr->sadb_msg_pid = pfk->dump.msg_portid;
 
 	if (pfk->dump.skb)
-		pfkey_broadcast(pfk->dump.skb, BROADCAST_ONE,
+		pfkey_broadcast(pfk->dump.skb, GFP_ATOMIC, BROADCAST_ONE,
 				&pfk->sk, sock_net(&pfk->sk));
 	pfk->dump.skb = out_skb;
 
@@ -1886,7 +1887,7 @@ static int pfkey_promisc(struct sock *sk
 		new_hdr->sadb_msg_errno = 0;
 	}
 
-	pfkey_broadcast(skb, BROADCAST_ALL, NULL, sock_net(sk));
+	pfkey_broadcast(skb, GFP_KERNEL, BROADCAST_ALL, NULL, sock_net(sk));
 	return 0;
 }
 
@@ -2219,7 +2220,7 @@ static int key_notify_policy(struct xfrm
 	out_hdr->sadb_msg_errno = 0;
 	out_hdr->sadb_msg_seq = c->seq;
 	out_hdr->sadb_msg_pid = c->portid;
-	pfkey_broadcast(out_skb, BROADCAST_ALL, NULL, xp_net(xp));
+	pfkey_broadcast(out_skb, GFP_ATOMIC, BROADCAST_ALL, NULL, xp_net(xp));
 	return 0;
 
 }
@@ -2439,7 +2440,7 @@ static int key_pol_get_resp(struct sock
 	out_hdr->sadb_msg_errno = 0;
 	out_hdr->sadb_msg_seq = hdr->sadb_msg_seq;
 	out_hdr->sadb_msg_pid = hdr->sadb_msg_pid;
-	pfkey_broadcast(out_skb, BROADCAST_ONE, sk, xp_net(xp));
+	pfkey_broadcast(out_skb, GFP_ATOMIC, BROADCAST_ONE, sk, xp_net(xp));
 	err = 0;
 
 out:
@@ -2695,7 +2696,7 @@ static int dump_sp(struct xfrm_policy *x
 	out_hdr->sadb_msg_pid = pfk->dump.msg_portid;
 
 	if (pfk->dump.skb)
-		pfkey_broadcast(pfk->dump.skb, BROADCAST_ONE,
+		pfkey_broadcast(pfk->dump.skb, GFP_ATOMIC, BROADCAST_ONE,
 				&pfk->sk, sock_net(&pfk->sk));
 	pfk->dump.skb = out_skb;
 
@@ -2752,7 +2753,7 @@ static int key_notify_policy_flush(const
 	hdr->sadb_msg_satype = SADB_SATYPE_UNSPEC;
 	hdr->sadb_msg_len = (sizeof(struct sadb_msg) / sizeof(uint64_t));
 	hdr->sadb_msg_reserved = 0;
-	pfkey_broadcast(skb_out, BROADCAST_ALL, NULL, c->net);
+	pfkey_broadcast(skb_out, GFP_ATOMIC, BROADCAST_ALL, NULL, c->net);
 	return 0;
 
 }
@@ -2814,7 +2815,7 @@ static int pfkey_process(struct sock *sk
 	void *ext_hdrs[SADB_EXT_MAX];
 	int err;
 
-	pfkey_broadcast(skb_clone(skb, GFP_KERNEL),
+	pfkey_broadcast(skb_clone(skb, GFP_KERNEL), GFP_KERNEL,
 			BROADCAST_PROMISC_ONLY, NULL, sock_net(sk));
 
 	memset(ext_hdrs, 0, sizeof(ext_hdrs));
@@ -3036,7 +3037,8 @@ static int key_notify_sa_expire(struct x
 	out_hdr->sadb_msg_seq = 0;
 	out_hdr->sadb_msg_pid = 0;
 
-	pfkey_broadcast(out_skb, BROADCAST_REGISTERED, NULL, xs_net(x));
+	pfkey_broadcast(out_skb, GFP_ATOMIC, BROADCAST_REGISTERED, NULL,
+			xs_net(x));
 	return 0;
 }
 
@@ -3226,7 +3228,8 @@ static int pfkey_send_acquire(struct xfr
 		       xfrm_ctx->ctx_len);
 	}
 
-	return pfkey_broadcast(skb, BROADCAST_REGISTERED, NULL, xs_net(x));
+	return pfkey_broadcast(skb, GFP_ATOMIC, BROADCAST_REGISTERED, NULL,
+			       xs_net(x));
 }
 
 static struct xfrm_policy *pfkey_compile_policy(struct sock *sk, int opt,
@@ -3424,7 +3427,8 @@ static int pfkey_send_new_mapping(struct
 	n_port->sadb_x_nat_t_port_port = sport;
 	n_port->sadb_x_nat_t_port_reserved = 0;
 
-	return pfkey_broadcast(skb, BROADCAST_REGISTERED, NULL, xs_net(x));
+	return pfkey_broadcast(skb, GFP_ATOMIC, BROADCAST_REGISTERED, NULL,
+			       xs_net(x));
 }
 
 #ifdef CONFIG_NET_KEY_MIGRATE
@@ -3616,7 +3620,7 @@ static int pfkey_send_migrate(const stru
 	}
 
 	/* broadcast migrate message to sockets */
-	pfkey_broadcast(skb, BROADCAST_ALL, NULL, &init_net);
+	pfkey_broadcast(skb, GFP_ATOMIC, BROADCAST_ALL, NULL, &init_net);
 
 	return 0;
 

  reply	other threads:[~2017-08-28  8:13 UTC|newest]

Thread overview: 62+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-08-28  8:05 [PATCH 4.4 00/53] 4.4.85-stable review Greg Kroah-Hartman
2017-08-28  8:05 ` Greg Kroah-Hartman [this message]
2017-08-28  8:05 ` [PATCH 4.4 02/53] dccp: purge write queue in dccp_destroy_sock() Greg Kroah-Hartman
2017-08-28  8:05 ` [PATCH 4.4 03/53] dccp: defer ccid_hc_tx_delete() at dismantle time Greg Kroah-Hartman
2017-08-28  8:05 ` [PATCH 4.4 04/53] ipv4: fix NULL dereference in free_fib_info_rcu() Greg Kroah-Hartman
2017-08-28  8:05 ` [PATCH 4.4 05/53] net_sched/sfq: update hierarchical backlog when drop packet Greg Kroah-Hartman
2017-08-28  8:05 ` [PATCH 4.4 06/53] ipv4: better IP_MAX_MTU enforcement Greg Kroah-Hartman
2017-08-28  8:05 ` [PATCH 4.4 07/53] sctp: fully initialize the IPv6 address in sctp_v6_to_addr() Greg Kroah-Hartman
2017-08-28  8:05 ` [PATCH 4.4 08/53] tipc: fix use-after-free Greg Kroah-Hartman
2017-08-28  8:05 ` [PATCH 4.4 09/53] ipv6: reset fn->rr_ptr when replacing route Greg Kroah-Hartman
2017-08-28  8:05 ` [PATCH 4.4 10/53] ipv6: repair fib6 tree in failure case Greg Kroah-Hartman
2017-08-28  8:05 ` [PATCH 4.4 11/53] tcp: when rearming RTO, if RTO time is in past then fire RTO ASAP Greg Kroah-Hartman
2017-08-28  8:05 ` [PATCH 4.4 12/53] irda: do not leak initialized list.dev to userspace Greg Kroah-Hartman
2017-08-28  8:05 ` [PATCH 4.4 13/53] net: sched: fix NULL pointer dereference when action calls some targets Greg Kroah-Hartman
2017-08-28  8:05 ` [PATCH 4.4 14/53] net_sched: fix order of queue length updates in qdisc_replace() Greg Kroah-Hartman
2017-08-28  8:05 ` [PATCH 4.4 15/53] mei: me: add broxton pci device ids Greg Kroah-Hartman
2017-08-28  8:05 ` [PATCH 4.4 16/53] mei: me: add lewisburg " Greg Kroah-Hartman
2017-08-28  8:05 ` [PATCH 4.4 17/53] Input: trackpoint - add new trackpoint firmware ID Greg Kroah-Hartman
2017-08-28  8:05 ` [PATCH 4.4 18/53] Input: elan_i2c - add ELAN0602 ACPI ID to support Lenovo Yoga310 Greg Kroah-Hartman
2017-08-28  8:05 ` [PATCH 4.4 19/53] ALSA: core: Fix unexpected error at replacing user TLV Greg Kroah-Hartman
2017-08-28  8:05 ` [PATCH 4.4 20/53] ALSA: hda - Add stereo mic quirk for Lenovo G50-70 (17aa:3978) Greg Kroah-Hartman
2017-08-28  8:05 ` [PATCH 4.4 21/53] ARCv2: PAE40: Explicitly set MSB counterpart of SLC region ops addresses Greg Kroah-Hartman
2017-08-28  8:05 ` [PATCH 4.4 22/53] i2c: designware: Fix system suspend Greg Kroah-Hartman
2017-08-28  8:05 ` [PATCH 4.4 24/53] drm/atomic: If the atomic check fails, return its value first Greg Kroah-Hartman
2017-08-28  8:05 ` [PATCH 4.4 25/53] drm: rcar-du: lvds: Fix PLL frequency-related configuration Greg Kroah-Hartman
2017-08-28  8:05 ` [PATCH 4.4 26/53] drm: rcar-du: lvds: Rename PLLEN bit to PLLON Greg Kroah-Hartman
2017-08-28  8:05 ` [PATCH 4.4 27/53] drm: rcar-du: Fix crash in encoder failure error path Greg Kroah-Hartman
2017-08-28  8:05 ` [PATCH 4.4 28/53] drm: rcar-du: Fix display timing controller parameter Greg Kroah-Hartman
2017-08-28  8:05 ` [PATCH 4.4 29/53] drm: rcar-du: Fix H/V sync signal polarity configuration Greg Kroah-Hartman
2017-08-28  8:05 ` [PATCH 4.4 30/53] tracing: Fix freeing of filter in create_filter() when set_str is false Greg Kroah-Hartman
2017-08-28  8:05 ` [PATCH 4.4 31/53] cifs: Fix df output for users with quota limits Greg Kroah-Hartman
2017-08-28  8:05 ` [PATCH 4.4 32/53] cifs: return ENAMETOOLONG for overlong names in cifs_open()/cifs_lookup() Greg Kroah-Hartman
2017-10-11 19:24   ` Ben Hutchings
2017-08-28  8:05 ` [PATCH 4.4 33/53] nfsd: Limit end of page list when decoding NFSv4 WRITE Greg Kroah-Hartman
2017-08-28  8:05 ` [PATCH 4.4 34/53] perf/core: Fix group {cpu,task} validation Greg Kroah-Hartman
2017-08-28  8:05 ` [PATCH 4.4 35/53] Bluetooth: hidp: fix possible might sleep error in hidp_session_thread Greg Kroah-Hartman
2017-09-26 15:32   ` Ben Hutchings
2017-08-28  8:05 ` [PATCH 4.4 36/53] Bluetooth: cmtp: fix possible might sleep error in cmtp_session Greg Kroah-Hartman
2017-08-28  8:05 ` [PATCH 4.4 37/53] Bluetooth: bnep: fix possible might sleep error in bnep_session Greg Kroah-Hartman
2017-08-28  8:05 ` [PATCH 4.4 38/53] binder: use group leader instead of open thread Greg Kroah-Hartman
2017-08-28  8:05 ` [PATCH 4.4 39/53] binder: Use wake up hint for synchronous transactions Greg Kroah-Hartman
2017-08-28  8:05 ` [PATCH 4.4 40/53] ANDROID: binder: fix proc->tsk check Greg Kroah-Hartman
2017-08-28  8:05 ` [PATCH 4.4 41/53] iio: imu: adis16480: Fix acceleration scale factor for adis16480 Greg Kroah-Hartman
2017-08-28  8:05 ` [PATCH 4.4 42/53] iio: hid-sensor-trigger: Fix the race with user space powering up sensors Greg Kroah-Hartman
2017-08-28  8:05 ` [PATCH 4.4 43/53] staging: rtl8188eu: add RNX-N150NUB support Greg Kroah-Hartman
2017-08-28  8:05 ` [PATCH 4.4 44/53] ASoC: simple-card: dont fail if sysclk setting is not supported Greg Kroah-Hartman
2017-08-28  8:05 ` [PATCH 4.4 45/53] ASoC: rsnd: disable SRC.out only when stop timing Greg Kroah-Hartman
2017-08-28  8:05 ` [PATCH 4.4 46/53] ASoC: rsnd: avoid pointless loop in rsnd_mod_interrupt() Greg Kroah-Hartman
2017-08-28  8:05 ` [PATCH 4.4 47/53] ASoC: rsnd: Add missing initialization of ADG req_rate Greg Kroah-Hartman
2017-08-28  8:05 ` [PATCH 4.4 48/53] ASoC: rsnd: ssi: 24bit data needs right-aligned settings Greg Kroah-Hartman
2017-08-28  8:05 ` [PATCH 4.4 49/53] ASoC: rsnd: dont call update callback if it was NULL Greg Kroah-Hartman
2017-08-28  8:05 ` [PATCH 4.4 50/53] ntb_transport: fix qp count bug Greg Kroah-Hartman
2017-09-26 16:32   ` Ben Hutchings
2017-09-26 17:35     ` Logan Gunthorpe
2017-09-27  8:40       ` Greg Kroah-Hartman
2017-09-27 15:57         ` Logan Gunthorpe
2017-09-28  8:14           ` Greg Kroah-Hartman
2017-08-28  8:05 ` [PATCH 4.4 51/53] ntb_transport: fix bug calculating num_qps_mw Greg Kroah-Hartman
2017-08-28  8:05 ` [PATCH 4.4 52/53] ACPI: ioapic: Clear on-stack resource before using it Greg Kroah-Hartman
2017-08-28  8:05 ` [PATCH 4.4 53/53] ACPI / APEI: Add missing synchronize_rcu() on NOTIFY_SCI removal Greg Kroah-Hartman
2017-08-28 19:39 ` [PATCH 4.4 00/53] 4.4.85-stable review Shuah Khan
2017-08-29  0:09 ` Guenter Roeck

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20170828080517.671416691@linuxfoundation.org \
    --to=gregkh@linuxfoundation.org \
    --cc=davem@davemloft.net \
    --cc=dsa@cumulusnetworks.com \
    --cc=dsahern@gmail.com \
    --cc=dvyukov@google.com \
    --cc=edumazet@google.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=stable@vger.kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).