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Message-Id: <20200122064729.117730-1-edumazet@google.com>
Date: Tue, 21 Jan 2020 22:47:29 -0800
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>
Cc: netdev <netdev@...r.kernel.org>,
Eric Dumazet <edumazet@...gle.com>,
Eric Dumazet <eric.dumazet@...il.com>,
syzbot <syzkaller@...glegroups.com>
Subject: [PATCH net] net: rtnetlink: validate IFLA_MTU attribute in rtnl_create_link()
rtnl_create_link() needs to apply dev->min_mtu and dev->max_mtu
checks that we apply in do_setlink()
Otherwise malicious users can crash the kernel, for example after
an integer overflow :
BUG: KASAN: use-after-free in memset include/linux/string.h:365 [inline]
BUG: KASAN: use-after-free in __alloc_skb+0x37b/0x5e0 net/core/skbuff.c:238
Write of size 32 at addr ffff88819f20b9c0 by task swapper/0/0
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.5.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
<IRQ>
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x197/0x210 lib/dump_stack.c:118
print_address_description.constprop.0.cold+0xd4/0x30b mm/kasan/report.c:374
__kasan_report.cold+0x1b/0x41 mm/kasan/report.c:506
kasan_report+0x12/0x20 mm/kasan/common.c:639
check_memory_region_inline mm/kasan/generic.c:185 [inline]
check_memory_region+0x134/0x1a0 mm/kasan/generic.c:192
memset+0x24/0x40 mm/kasan/common.c:108
memset include/linux/string.h:365 [inline]
__alloc_skb+0x37b/0x5e0 net/core/skbuff.c:238
alloc_skb include/linux/skbuff.h:1049 [inline]
alloc_skb_with_frags+0x93/0x590 net/core/skbuff.c:5664
sock_alloc_send_pskb+0x7ad/0x920 net/core/sock.c:2242
sock_alloc_send_skb+0x32/0x40 net/core/sock.c:2259
mld_newpack+0x1d7/0x7f0 net/ipv6/mcast.c:1609
add_grhead.isra.0+0x299/0x370 net/ipv6/mcast.c:1713
add_grec+0x7db/0x10b0 net/ipv6/mcast.c:1844
mld_send_cr net/ipv6/mcast.c:1970 [inline]
mld_ifc_timer_expire+0x3d3/0x950 net/ipv6/mcast.c:2477
call_timer_fn+0x1ac/0x780 kernel/time/timer.c:1404
expire_timers kernel/time/timer.c:1449 [inline]
__run_timers kernel/time/timer.c:1773 [inline]
__run_timers kernel/time/timer.c:1740 [inline]
run_timer_softirq+0x6c3/0x1790 kernel/time/timer.c:1786
__do_softirq+0x262/0x98c kernel/softirq.c:292
invoke_softirq kernel/softirq.c:373 [inline]
irq_exit+0x19b/0x1e0 kernel/softirq.c:413
exiting_irq arch/x86/include/asm/apic.h:536 [inline]
smp_apic_timer_interrupt+0x1a3/0x610 arch/x86/kernel/apic/apic.c:1137
apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:829
</IRQ>
RIP: 0010:native_safe_halt+0xe/0x10 arch/x86/include/asm/irqflags.h:61
Code: 98 6b ea f9 eb 8a cc cc cc cc cc cc e9 07 00 00 00 0f 00 2d 44 1c 60 00 f4 c3 66 90 e9 07 00 00 00 0f 00 2d 34 1c 60 00 fb f4 <c3> cc 55 48 89 e5 41 57 41 56 41 55 41 54 53 e8 4e 5d 9a f9 e8 79
RSP: 0018:ffffffff89807ce8 EFLAGS: 00000286 ORIG_RAX: ffffffffffffff13
RAX: 1ffffffff13266ae RBX: ffffffff8987a1c0 RCX: 0000000000000000
RDX: dffffc0000000000 RSI: 0000000000000006 RDI: ffffffff8987aa54
RBP: ffffffff89807d18 R08: ffffffff8987a1c0 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: dffffc0000000000
R13: ffffffff8a799980 R14: 0000000000000000 R15: 0000000000000000
arch_cpu_idle+0xa/0x10 arch/x86/kernel/process.c:690
default_idle_call+0x84/0xb0 kernel/sched/idle.c:94
cpuidle_idle_call kernel/sched/idle.c:154 [inline]
do_idle+0x3c8/0x6e0 kernel/sched/idle.c:269
cpu_startup_entry+0x1b/0x20 kernel/sched/idle.c:361
rest_init+0x23b/0x371 init/main.c:451
arch_call_rest_init+0xe/0x1b
start_kernel+0x904/0x943 init/main.c:784
x86_64_start_reservations+0x29/0x2b arch/x86/kernel/head64.c:490
x86_64_start_kernel+0x77/0x7b arch/x86/kernel/head64.c:471
secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:242
The buggy address belongs to the page:
page:ffffea00067c82c0 refcount:0 mapcount:0 mapping:0000000000000000 index:0x0
raw: 057ffe0000000000 ffffea00067c82c8 ffffea00067c82c8 0000000000000000
raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
Memory state around the buggy address:
ffff88819f20b880: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ffff88819f20b900: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff88819f20b980: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
^
ffff88819f20ba00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ffff88819f20ba80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
Fixes: 61e84623ace3 ("net: centralize net_device min/max MTU checking")
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Reported-by: syzbot <syzkaller@...glegroups.com>
---
include/linux/netdevice.h | 2 ++
net/core/dev.c | 29 +++++++++++++++++++----------
net/core/rtnetlink.c | 13 +++++++++++--
3 files changed, 32 insertions(+), 12 deletions(-)
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index ae5e260911e289a2f9b20db71268ac0a0755f9fc..cac56fb59af85cf25c3e3b3e18faae58248c801d 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -3698,6 +3698,8 @@ int dev_set_alias(struct net_device *, const char *, size_t);
int dev_get_alias(const struct net_device *, char *, size_t);
int dev_change_net_namespace(struct net_device *, struct net *, const char *);
int __dev_set_mtu(struct net_device *, int);
+int dev_validate_mtu(struct net_device *dev, int mtu,
+ struct netlink_ext_ack *extack);
int dev_set_mtu_ext(struct net_device *dev, int mtu,
struct netlink_ext_ack *extack);
int dev_set_mtu(struct net_device *, int);
diff --git a/net/core/dev.c b/net/core/dev.c
index e82e9b82dfd93f28ebbdb64b11a86ab7ab473a99..767456b66eb76085dafd60bc93a4759c63481338 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -8194,6 +8194,22 @@ int __dev_set_mtu(struct net_device *dev, int new_mtu)
}
EXPORT_SYMBOL(__dev_set_mtu);
+int dev_validate_mtu(struct net_device *dev, int new_mtu,
+ struct netlink_ext_ack *extack)
+{
+ /* MTU must be positive, and in range */
+ if (new_mtu < 0 || new_mtu < dev->min_mtu) {
+ NL_SET_ERR_MSG(extack, "mtu less than device minimum");
+ return -EINVAL;
+ }
+
+ if (dev->max_mtu > 0 && new_mtu > dev->max_mtu) {
+ NL_SET_ERR_MSG(extack, "mtu greater than device maximum");
+ return -EINVAL;
+ }
+ return 0;
+}
+
/**
* dev_set_mtu_ext - Change maximum transfer unit
* @dev: device
@@ -8210,16 +8226,9 @@ int dev_set_mtu_ext(struct net_device *dev, int new_mtu,
if (new_mtu == dev->mtu)
return 0;
- /* MTU must be positive, and in range */
- if (new_mtu < 0 || new_mtu < dev->min_mtu) {
- NL_SET_ERR_MSG(extack, "mtu less than device minimum");
- return -EINVAL;
- }
-
- if (dev->max_mtu > 0 && new_mtu > dev->max_mtu) {
- NL_SET_ERR_MSG(extack, "mtu greater than device maximum");
- return -EINVAL;
- }
+ err = dev_validate_mtu(dev, new_mtu, extack);
+ if (err)
+ return err;
if (!netif_device_present(dev))
return -ENODEV;
diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index 02916f43bf63cdbdd7d2c7e030776d7203421232..d9001b5c48eb4e1af583f2d186451be592622e9d 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -3048,8 +3048,17 @@ struct net_device *rtnl_create_link(struct net *net, const char *ifname,
dev->rtnl_link_ops = ops;
dev->rtnl_link_state = RTNL_LINK_INITIALIZING;
- if (tb[IFLA_MTU])
- dev->mtu = nla_get_u32(tb[IFLA_MTU]);
+ if (tb[IFLA_MTU]) {
+ u32 mtu = nla_get_u32(tb[IFLA_MTU]);
+ int err;
+
+ err = dev_validate_mtu(dev, mtu, extack);
+ if (err) {
+ free_netdev(dev);
+ return ERR_PTR(err);
+ }
+ dev->mtu = mtu;
+ }
if (tb[IFLA_ADDRESS]) {
memcpy(dev->dev_addr, nla_data(tb[IFLA_ADDRESS]),
nla_len(tb[IFLA_ADDRESS]));
--
2.25.0.341.g760bfbb309-goog
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