netdev - net/ipv4: null-ptr-deref in udp_rmem_release/sk_memory_allocated

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Date:   Thu, 9 Feb 2017 13:28:08 +0100
From:   Andrey Konovalov <andreyknvl@...gle.com>
To:     "David S. Miller" <davem@...emloft.net>,
        Alexey Kuznetsov <kuznet@....inr.ac.ru>,
        James Morris <jmorris@...ei.org>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        Patrick McHardy <kaber@...sh.net>,
        netdev <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Cc:     Dmitry Vyukov <dvyukov@...gle.com>,
        Kostya Serebryany <kcc@...gle.com>,
        Eric Dumazet <edumazet@...gle.com>,
        syzkaller <syzkaller@...glegroups.com>
Subject: net/ipv4: null-ptr-deref in udp_rmem_release/sk_memory_allocated_sub

Hi,

I've got the following error report while fuzzing the kernel with syzkaller.

On commit 926af6273fc683cd98cd0ce7bf0d04a02eed6742.

A reproducer and .config are attached.

BUG: unable to handle kernel NULL pointer dereference at           (null)
IP: sk_memory_allocated_sub include/net/sock.h:1214 [inline]
IP: __sk_mem_reduce_allocated+0xa9/0x390 net/core/sock.c:2215
PGD 3aa86067
PUD 33243067
PMD 0

Oops: 0002 [#1] SMP KASAN
Dumping ftrace buffer:
   (ftrace buffer empty)
Modules linked in:
CPU: 3 PID: 13215 Comm: syz-executor5 Not tainted 4.10.0-rc7+ #126
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
task: ffff88006bf59700 task.stack: ffff88005e0a8000
RIP: 0010:sk_memory_allocated_sub include/net/sock.h:1214 [inline]
RIP: 0010:__sk_mem_reduce_allocated+0xa9/0x390 net/core/sock.c:2215
RSP: 0018:ffff88005e0afa48 EFLAGS: 00010246
RAX: 0000000000000000 RBX: 1ffff1000bc15f4a RCX: 1ffffffff0bc7d8e
RDX: dffffc0000000000 RSI: ffffffff83343399 RDI: ffffffff85e3ec70
RBP: ffff88005e0afad8 R08: 0000000000000090 R09: 0000000000000000
R10: 0000000000000002 R11: 0000000000000000 R12: ffff88003dfb3c40
R13: 000000000003dfb4 R14: ffff88003dfb3c68 R15: ffffffff85e3eba0
FS:  00007f71b9ba9700(0000) GS:ffff88006df00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 00000000393b8000 CR4: 00000000000006e0
Call Trace:
 udp_rmem_release+0x14f/0x180 net/ipv4/udp.c:1199
 first_packet_length+0x215/0x6e0 net/ipv4/udp.c:1380
 udp_ioctl+0x13f/0x2c0 net/ipv4/udp.c:1401
 inet6_ioctl+0x19e/0x1e0 net/ipv6/af_inet6.c:530
 sock_do_ioctl+0x65/0xb0 net/socket.c:897
 sock_ioctl+0x28f/0x440 net/socket.c:995
 vfs_ioctl fs/ioctl.c:43 [inline]
 do_vfs_ioctl+0x1bf/0x1780 fs/ioctl.c:683
 SYSC_ioctl fs/ioctl.c:698 [inline]
 SyS_ioctl+0x8f/0xc0 fs/ioctl.c:689
 entry_SYSCALL_64_fastpath+0x1f/0xc2
RIP: 0033:0x4458b9
RSP: 002b:00007f71b9ba8b58 EFLAGS: 00000286 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000005 RCX: 00000000004458b9
RDX: 0000000020005f3e RSI: 000000000000541b RDI: 0000000000000005
RBP: 00000000006e0cc0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000286 R12: 00000000007080a8
R13: 0000000000000000 R14: 00007f71b9ba99c0 R15: 00007f71b9ba9700
Code: 24 28 48 ba 00 00 00 00 00 fc ff df 49 8d bf d0 00 00 00 48 89
f9 48 c1 e9 03 80 3c 11 00 0f 85 8b 02 00 00 49 8b 87 d0 00 00 00 <f0>
4c 29 28 4d 8b 7c 24 28 48 ba 00 00 00 00 00 fc ff df 49 8d
RIP: sk_memory_allocated_sub include/net/sock.h:1214 [inline] RSP:
ffff88005e0afa48
RIP: __sk_mem_reduce_allocated+0xa9/0x390 net/core/sock.c:2215 RSP:
ffff88005e0afa48
CR2: 0000000000000000
---[ end trace 8b75e9ae315695b0 ]---
Kernel panic - not syncing: Fatal exception in interrupt
Dumping ftrace buffer:
   (ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..

View attachment "ipv4-rmem-null-poc.c" of type "text/x-csrc" (8752 bytes)

Download attachment ".config" of type "application/octet-stream" (124975 bytes)