netdev - Re: [PATCH] ravb: Fix use-after-free on `ifconfig eth0 down`

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Message-ID: <eaf9aa22-9087-977b-b048-3d1906176d1a@cogentembedded.com>
Date:   Tue, 6 Jun 2017 12:35:30 +0300
From:   Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
To:     Eugeniu Rosca <erosca@...adit-jv.com>, davem@...emloft.net,
        horms+renesas@...ge.net.au, kazuya.mizuguchi.ks@...esas.com
Cc:     netdev@...r.kernel.org, linux-renesas-soc@...r.kernel.org
Subject: Re: [PATCH] ravb: Fix use-after-free on `ifconfig eth0 down`

Hello!

On 6/6/2017 1:08 AM, Eugeniu Rosca wrote:

> Commit a47b70ea86bd ("ravb: unmap descriptors when freeing rings") has
> introduced the issue seen in [1] reproduced on H3ULCB board.
>
> Fix this by relocating the RX skb ringbuffer free operation, so that
> swiotlb page unmapping can be done first. Freeing of aligned TX buffers
> is not relevant to the issue seen in [1]. Still, reposition TX free
> calls as well, to have all kfree() operations performed consistently
> _after_ dma_unmap_*()/dma_free_*().

    Perhaps it's a material of a separate cleanup patch?

> [1] Console screenshot with the problem reproduced:
>
> salvator-x login: root
> root@...vator-x:~# ifconfig eth0 up
> Micrel KSZ9031 Gigabit PHY e6800000.ethernet-ffffffff:00: \
>        attached PHY driver [Micrel KSZ9031 Gigabit PHY]   \
>        (mii_bus:phy_addr=e6800000.ethernet-ffffffff:00, irq=235)
> IPv6: ADDRCONF(NETDEV_UP): eth0: link is not ready
> root@...vator-x:~#
> root@...vator-x:~# ifconfig eth0 down
> ==================================================================
> BUG: KASAN: use-after-free in swiotlb_tbl_unmap_single+0xc4/0x35c
> Write of size 1538 at addr ffff8006d884f780 by task ifconfig/1649
>
> CPU: 0 PID: 1649 Comm: ifconfig Not tainted 4.12.0-rc4-00004-g112eb07287d1 #32
> Hardware name: Renesas H3ULCB board based on r8a7795 (DT)
> Call trace:
> [<ffff20000808f11c>] dump_backtrace+0x0/0x3a4
> [<ffff20000808f4d4>] show_stack+0x14/0x1c
> [<ffff20000865970c>] dump_stack+0xf8/0x150
> [<ffff20000831f8b0>] print_address_description+0x7c/0x330
> [<ffff200008320010>] kasan_report+0x2e0/0x2f4
> [<ffff20000831eac0>] check_memory_region+0x20/0x14c
> [<ffff20000831f054>] memcpy+0x48/0x68
> [<ffff20000869ed50>] swiotlb_tbl_unmap_single+0xc4/0x35c
> [<ffff20000869fcf4>] unmap_single+0x90/0xa4
> [<ffff20000869fd14>] swiotlb_unmap_page+0xc/0x14
> [<ffff2000080a2974>] __swiotlb_unmap_page+0xcc/0xe4
> [<ffff2000088acdb8>] ravb_ring_free+0x514/0x870
> [<ffff2000088b25dc>] ravb_close+0x288/0x36c
> [<ffff200008aaf8c4>] __dev_close_many+0x14c/0x174
> [<ffff200008aaf9b4>] __dev_close+0xc8/0x144
> [<ffff200008ac2100>] __dev_change_flags+0xd8/0x194
> [<ffff200008ac221c>] dev_change_flags+0x60/0xb0
> [<ffff200008ba2dec>] devinet_ioctl+0x484/0x9d4
> [<ffff200008ba7b78>] inet_ioctl+0x190/0x194
> [<ffff200008a78c44>] sock_do_ioctl+0x78/0xa8
> [<ffff200008a7a128>] sock_ioctl+0x110/0x3c4
> [<ffff200008365a70>] vfs_ioctl+0x90/0xa0
> [<ffff200008365dbc>] do_vfs_ioctl+0x148/0xc38
> [<ffff2000083668f0>] SyS_ioctl+0x44/0x74
> [<ffff200008083770>] el0_svc_naked+0x24/0x28
>
> The buggy address belongs to the page:
> page:ffff7e001b6213c0 count:0 mapcount:0 mapping:          (null) index:0x0
> flags: 0x4000000000000000()
> raw: 4000000000000000 0000000000000000 0000000000000000 00000000ffffffff
> raw: 0000000000000000 ffff7e001b6213e0 0000000000000000 0000000000000000
> page dumped because: kasan: bad access detected
>
> Memory state around the buggy address:
>  ffff8006d884f680: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>  ffff8006d884f700: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>> ffff8006d884f780: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>                    ^
>  ffff8006d884f800: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>  ffff8006d884f880: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
> ==================================================================
> Disabling lock debugging due to kernel taint
> root@...vator-x:~#
>
> Fixes: a47b70ea86bd ("ravb: unmap descriptors when freeing rings")
> Signed-off-by: Eugeniu Rosca <erosca@...adit-jv.com>
[...]

Acked-by: Sergei Shtylyov <sergei.shtylyov@...entembedded.com>

MBR, Sergei