Re: [PATCH net] net/sched: fix NULL dereference in the error path of tcf_vlan_init()

[Jiri Pirko <jiri@resnulli.us>]

Thu, Mar 15, 2018 at 03:06:30PM CET, dcaratti@redhat.com wrote:
>when the following command
>
> # tc actions replace action vlan pop index 100
>
>is run for the first time, and tcf_vlan_init() fails allocating struct
>tcf_vlan_params, tcf_vlan_cleanup() calls kfree_rcu(NULL, ...). This causes
>the following error:
>
> BUG: unable to handle kernel NULL pointer dereference at 0000000000000018
> IP: __call_rcu+0x23/0x2b0
> PGD 80000000760a2067 P4D 80000000760a2067 PUD 742c1067 PMD 0
> Oops: 0002 [#1] SMP PTI
> Modules linked in: act_vlan(E) ip6table_filter ip6_tables iptable_filter binfmt_misc ext4 snd_hda_codec_generic snd_hda_intel mbcache snd_hda_codec jbd2 snd_hda_core crct10dif_pclmul crc32_pclmul ghash_clmulni_intel pcbc snd_hwdep snd_seq snd_seq_device snd_pcm aesni_intel crypto_simd snd_timer glue_helper snd cryptd joydev soundcore virtio_balloon pcspkr i2c_piix4 nfsd auth_rpcgss nfs_acl lockd grace sunrpc ip_tables xfs libcrc32c ata_generic pata_acpi qxl drm_kms_helper syscopyarea sysfillrect sysimgblt fb_sys_fops ttm drm virtio_console virtio_blk virtio_net ata_piix crc32c_intel libata virtio_pci i2c_core virtio_ring serio_raw virtio floppy dm_mirror dm_region_hash dm_log dm_mod [last unloaded: act_vlan]
> CPU: 3 PID: 3119 Comm: tc Tainted: G            E    4.16.0-rc4.act_vlan.orig+ #403
> Hardware name: Red Hat KVM, BIOS 0.5.1 01/01/2011
> RIP: 0010:__call_rcu+0x23/0x2b0
> RSP: 0018:ffffaac3005fb798 EFLAGS: 00010246
> RAX: ffffffffc0704080 RBX: ffff97f2b4bbe900 RCX: 00000000ffffffff
> RDX: ffffffffabca5f00 RSI: 0000000000000010 RDI: 0000000000000010
> RBP: 0000000000000010 R08: 0000000000000001 R09: 0000000000000044
> R10: 00000000fd003000 R11: ffff97f2faab5b91 R12: 0000000000000000
> R13: ffffffffabca5f00 R14: ffff97f2fb80202c R15: 00000000fffffff4
> FS:  00007f68f75b4740(0000) GS:ffff97f2ffd80000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000000000000018 CR3: 0000000072b52001 CR4: 00000000001606e0
> Call Trace:
>  __tcf_idr_release+0x79/0xf0
>  tcf_vlan_init+0x168/0x270 [act_vlan]
>  tcf_action_init_1+0x2cc/0x430
>  tcf_action_init+0xd3/0x1b0
>  tc_ctl_action+0x18b/0x240
>  rtnetlink_rcv_msg+0x29c/0x310
>  ? _cond_resched+0x15/0x30
>  ? __kmalloc_node_track_caller+0x1b9/0x270
>  ? rtnl_calcit.isra.28+0x100/0x100
>  netlink_rcv_skb+0xd2/0x110
>  netlink_unicast+0x17c/0x230
>  netlink_sendmsg+0x2cd/0x3c0
>  sock_sendmsg+0x30/0x40
>  ___sys_sendmsg+0x27a/0x290
>  ? filemap_map_pages+0x34a/0x3a0
>  ? __handle_mm_fault+0xbfd/0xe20
>  __sys_sendmsg+0x51/0x90
>  do_syscall_64+0x6e/0x1a0
>  entry_SYSCALL_64_after_hwframe+0x3d/0xa2
> RIP: 0033:0x7f68f69c5ba0
> RSP: 002b:00007fffd79c1118 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
> RAX: ffffffffffffffda RBX: 00007fffd79c1240 RCX: 00007f68f69c5ba0
> RDX: 0000000000000000 RSI: 00007fffd79c1190 RDI: 0000000000000003
> RBP: 000000005aaa708e R08: 0000000000000002 R09: 0000000000000000
> R10: 00007fffd79c0ba0 R11: 0000000000000246 R12: 0000000000000000
> R13: 00007fffd79c1254 R14: 0000000000000001 R15: 0000000000669f60
> Code: 5d e9 42 da ff ff 66 90 0f 1f 44 00 00 41 57 41 56 41 55 49 89 d5 41 54 55 48 89 fd 53 48 83 ec 08 40 f6 c7 07 0f 85 19 02 00 00 <48> 89 75 08 48 c7 45 00 00 00 00 00 9c 58 0f 1f 44 00 00 49 89
> RIP: __call_rcu+0x23/0x2b0 RSP: ffffaac3005fb798
> CR2: 0000000000000018
>
>fix this in tcf_vlan_cleanup(), ensuring that kfree_rcu(p, ...) is called
>only when p is not NULL.
>
>Fixes: 4c5b9d9642c8 ("act_vlan: VLAN action rewrite to use RCU lock/unlock and update")
>Signed-off-by: Davide Caratti <dcaratti@redhat.com>

Acked-by: Jiri Pirko <jiri@mellanox.com>