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    Subject[PATCH 4.19 13/30] net-sysfs: add check for netdevice being present to speed_show
    Date
    From: suresh kumar <suresh2514@gmail.com>

    [ Upstream commit 4224cfd7fb6523f7a9d1c8bb91bb5df1e38eb624 ]

    When bringing down the netdevice or system shutdown, a panic can be
    triggered while accessing the sysfs path because the device is already
    removed.

    [ 755.549084] mlx5_core 0000:12:00.1: Shutdown was called
    [ 756.404455] mlx5_core 0000:12:00.0: Shutdown was called
    ...
    [ 757.937260] BUG: unable to handle kernel NULL pointer dereference at (null)
    [ 758.031397] IP: [<ffffffff8ee11acb>] dma_pool_alloc+0x1ab/0x280

    crash> bt
    ...
    PID: 12649 TASK: ffff8924108f2100 CPU: 1 COMMAND: "amsd"
    ...
    #9 [ffff89240e1a38b0] page_fault at ffffffff8f38c778
    [exception RIP: dma_pool_alloc+0x1ab]
    RIP: ffffffff8ee11acb RSP: ffff89240e1a3968 RFLAGS: 00010046
    RAX: 0000000000000246 RBX: ffff89243d874100 RCX: 0000000000001000
    RDX: 0000000000000000 RSI: 0000000000000246 RDI: ffff89243d874090
    RBP: ffff89240e1a39c0 R8: 000000000001f080 R9: ffff8905ffc03c00
    R10: ffffffffc04680d4 R11: ffffffff8edde9fd R12: 00000000000080d0
    R13: ffff89243d874090 R14: ffff89243d874080 R15: 0000000000000000
    ORIG_RAX: ffffffffffffffff CS: 0010 SS: 0018
    #10 [ffff89240e1a39c8] mlx5_alloc_cmd_msg at ffffffffc04680f3 [mlx5_core]
    #11 [ffff89240e1a3a18] cmd_exec at ffffffffc046ad62 [mlx5_core]
    #12 [ffff89240e1a3ab8] mlx5_cmd_exec at ffffffffc046b4fb [mlx5_core]
    #13 [ffff89240e1a3ae8] mlx5_core_access_reg at ffffffffc0475434 [mlx5_core]
    #14 [ffff89240e1a3b40] mlx5e_get_fec_caps at ffffffffc04a7348 [mlx5_core]
    #15 [ffff89240e1a3bb0] get_fec_supported_advertised at ffffffffc04992bf [mlx5_core]
    #16 [ffff89240e1a3c08] mlx5e_get_link_ksettings at ffffffffc049ab36 [mlx5_core]
    #17 [ffff89240e1a3ce8] __ethtool_get_link_ksettings at ffffffff8f25db46
    #18 [ffff89240e1a3d48] speed_show at ffffffff8f277208
    #19 [ffff89240e1a3dd8] dev_attr_show at ffffffff8f0b70e3
    #20 [ffff89240e1a3df8] sysfs_kf_seq_show at ffffffff8eedbedf
    #21 [ffff89240e1a3e18] kernfs_seq_show at ffffffff8eeda596
    #22 [ffff89240e1a3e28] seq_read at ffffffff8ee76d10
    #23 [ffff89240e1a3e98] kernfs_fop_read at ffffffff8eedaef5
    #24 [ffff89240e1a3ed8] vfs_read at ffffffff8ee4e3ff
    #25 [ffff89240e1a3f08] sys_read at ffffffff8ee4f27f
    #26 [ffff89240e1a3f50] system_call_fastpath at ffffffff8f395f92

    crash> net_device.state ffff89443b0c0000
    state = 0x5 (__LINK_STATE_START| __LINK_STATE_NOCARRIER)

    To prevent this scenario, we also make sure that the netdevice is present.

    Signed-off-by: suresh kumar <suresh2514@gmail.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    net/core/net-sysfs.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
    index e5dc04cb5599..7a11b2d90975 100644
    --- a/net/core/net-sysfs.c
    +++ b/net/core/net-sysfs.c
    @@ -203,7 +203,7 @@ static ssize_t speed_show(struct device *dev,
    if (!rtnl_trylock())
    return restart_syscall();

    - if (netif_running(netdev)) {
    + if (netif_running(netdev) && netif_device_present(netdev)) {
    struct ethtool_link_ksettings cmd;

    if (!__ethtool_get_link_ksettings(netdev, &cmd))
    --
    2.34.1


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