From: Eric Dumazet edumazet@google.com
[ Upstream commit d836f5c69d87473ff65c06a6123e5b2cf5e56f5b ]
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@google.com Reported-by: syzbot syzkaller@googlegroups.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- include/linux/netdevice.h | 2 ++ net/core/dev.c | 29 +++++++++++++++++++---------- net/core/rtnetlink.c | 13 +++++++++++-- 3 files changed, 32 insertions(+), 12 deletions(-)
--- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -3666,6 +3666,8 @@ int dev_set_alias(struct net_device *, c 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); --- a/net/core/dev.c +++ b/net/core/dev.c @@ -7973,6 +7973,22 @@ int __dev_set_mtu(struct net_device *dev } 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 @@ -7989,16 +8005,9 @@ int dev_set_mtu_ext(struct net_device *d 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; --- a/net/core/rtnetlink.c +++ b/net/core/rtnetlink.c @@ -2959,8 +2959,17 @@ struct net_device *rtnl_create_link(stru 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]));