Re: [PATCH 4.3 2/2] vrf: fix double free and memory corruption on register_netdevice failure

[Ben Hutchings]

Sorry, this was from me; I didn't mean to forge Nikolay's address.

Ben.

On Tue, 2015-12-15 at 15:32 +0000, Nikolay Aleksandrov wrote:
> commit 7f109f7cc37108cba7243bc832988525b0d85909 upstream.
> 
> When vrf's ->newlink is called, if register_netdevice() fails then it
> does free_netdev(), but that's also done by rtnl_newlink() so a
> second
> free happens and memory gets corrupted, to reproduce execute the
> following line a couple of times (1 - 5 usually is enough):
> $ for i in `seq 1 5`; do ip link add vrf: type vrf table 1; done;
> This works because we fail in register_netdevice() because of the
> wrong
> name "vrf:".
> 
> And here's a trace of one crash:
> [ÂÂÂ28.792157] ------------[ cut here ]------------
> [ÂÂÂ28.792407] kernel BUG at fs/namei.c:246!
> [ÂÂÂ28.792608] invalid opcode: 0000 [#1] SMP
> [ÂÂÂ28.793240] Modules linked in: vrf nfsd auth_rpcgss oid_registry
> nfs_acl nfs lockd grace sunrpc crct10dif_pclmul crc32_pclmul
> crc32c_intel qxl drm_kms_helper ttm drm aesni_intel aes_x86_64
> psmouse
> glue_helper lrw evdev gf128mul i2c_piix4 ablk_helper cryptd ppdev
> parport_pc parport serio_raw pcspkr virtio_balloon virtio_console
> i2c_core acpi_cpufreq button 9pnet_virtio 9p 9pnet fscache ipv6
> autofs4
> ext4 crc16 mbcache jbd2 virtio_blk virtio_net sg sr_mod cdrom
> ata_generic ehci_pci uhci_hcd ehci_hcd e1000 usbcore usb_common
> ata_piix
> libata virtio_pci virtio_ring virtio scsi_mod floppy
> [ÂÂÂ28.796016] CPU: 0 PID: 1148 Comm: ld-linux-x86-64 Not tainted
> 4.4.0-rc1+ #24
> [ÂÂÂ28.796016] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
> BIOS 1.8.1-20150318_183358- 04/01/2014
> [ÂÂÂ28.796016] task: ffff8800352561c0 ti: ffff88003592c000 task.ti:
> ffff88003592c000
> [ÂÂÂ28.796016] RIP: 0010:[<ffffffff812187b3>]ÂÂ[<ffffffff812187b3>]
> putname+0x43/0x60
> [ÂÂÂ28.796016] RSP: 0018:ffff88003592fe88ÂÂEFLAGS: 00010246
> [ÂÂÂ28.796016] RAX: 0000000000000000 RBX: ffff8800352561c0 RCX:
> 0000000000000001
> [ÂÂÂ28.796016] RDX: 0000000000000000 RSI: 0000000000000000 RDI:
> ffff88003784f000
> [ÂÂÂ28.796016] RBP: ffff88003592ff08 R08: 0000000000000001 R09:
> 0000000000000000
> [ÂÂÂ28.796016] R10: 0000000000000000 R11: 0000000000000001 R12:
> 0000000000000000
> [ÂÂÂ28.796016] R13: 000000000000047c R14: ffff88003784f000 R15:
> ffff8800358c4a00
> [ÂÂÂ28.796016] FS:ÂÂ0000000000000000(0000) GS:ffff88003fc00000(0000)
> knlGS:0000000000000000
> [ÂÂÂ28.796016] CS:ÂÂ0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [ÂÂÂ28.796016] CR2: 00007ffd583bc2d9 CR3: 0000000035a99000 CR4:
> 00000000000406f0
> [ÂÂÂ28.796016] Stack:
> [ÂÂÂ28.796016]ÂÂffffffff8121045d ffffffff812102d3 ffff8800352561c0
> ffff880035a91660
> [ÂÂÂ28.796016]ÂÂffff8800008a9880 0000000000000000 ffffffff81a49940
> 00ffffff81218684
> [ÂÂÂ28.796016]ÂÂffff8800352561c0 000000000000047c 0000000000000000
> ffff880035b36d80
> [ÂÂÂ28.796016] Call Trace:
> [ÂÂÂ28.796016]ÂÂ[<ffffffff8121045d>] ?
> do_execveat_common.isra.34+0x74d/0x930
> [ÂÂÂ28.796016]ÂÂ[<ffffffff812102d3>] ?
> do_execveat_common.isra.34+0x5c3/0x930
> [ÂÂÂ28.796016]ÂÂ[<ffffffff8121066c>] do_execve+0x2c/0x30
> [ÂÂÂ28.796016]ÂÂ[<ffffffff810939a0>]
> call_usermodehelper_exec_async+0xf0/0x140
> [ÂÂÂ28.796016]ÂÂ[<ffffffff810938b0>] ? umh_complete+0x40/0x40
> [ÂÂÂ28.796016]ÂÂ[<ffffffff815cb1af>] ret_from_fork+0x3f/0x70
> [ÂÂÂ28.796016] Code: 48 8d 47 1c 48 89 e5 53 48 8b 37 48 89 fb 48 39
> c6
> 74 1a 48 8b 3d 7e e9 8f 00 e8 49 fa fc ff 48 89 df e8 f1 01 fd ff 5b
> 5d
> f3 c3 <0f> 0b 48 89 fe 48 8b 3d 61 e9 8f 00 e8 2c fa fc ff 5b 5d eb
> e9
> [ÂÂÂ28.796016] RIPÂÂ[<ffffffff812187b3>] putname+0x43/0x60
> [ÂÂÂ28.796016]ÂÂRSP <ffff88003592fe88>
> 
> Fixes: 193125dbd8eb ("net: Introduce VRF device driver")
> Signed-off-by: Nikolay Aleksandrov <nikolay@xxxxxxxxxxxxxxxxxxx>
> Acked-by: David Ahern <dsa@xxxxxxxxxxxxxxxxxxx>
> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
> [bwh: For 4.3, retain the kfree() on failure]
> Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
> ---
> Âdrivers/net/vrf.c | 1 -
> Â1 file changed, 1 deletion(-)
> 
> diff --git a/drivers/net/vrf.c b/drivers/net/vrf.c
> index 488c6f5..374feba 100644
> --- a/drivers/net/vrf.c
> +++ b/drivers/net/vrf.c
> @@ -608,7 +608,6 @@ static int vrf_newlink(struct net *src_net,
> struct net_device *dev,
> Â
> Âout_fail:
> Â	kfree(vrf_ptr);
> -	free_netdev(dev);
> Â	return err;
> Â}
> Â
-- 
Ben Hutchings
Logic doesn't apply to the real world. - Marvin Minsky

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