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    Subject[PATCH 5.17 202/298] tty: synclink_gt: Fix null-pointer-dereference in slgt_clean()
    Date
    From: Zheyu Ma <zheyuma97@gmail.com>

    [ Upstream commit 689ca31c542687709ba21ec2195c1fbce34fd029 ]

    When the driver fails at alloc_hdlcdev(), and then we remove the driver
    module, we will get the following splat:

    [ 25.065966] general protection fault, probably for non-canonical address 0xdffffc0000000182: 0000 [#1] PREEMPT SMP KASAN PTI
    [ 25.066914] KASAN: null-ptr-deref in range [0x0000000000000c10-0x0000000000000c17]
    [ 25.069262] RIP: 0010:detach_hdlc_protocol+0x2a/0x3e0
    [ 25.077709] Call Trace:
    [ 25.077924] <TASK>
    [ 25.078108] unregister_hdlc_device+0x16/0x30
    [ 25.078481] slgt_cleanup+0x157/0x9f0 [synclink_gt]

    Fix this by checking whether the 'info->netdev' is a null pointer first.

    Reviewed-by: Jiri Slaby <jirislaby@kernel.org>
    Signed-off-by: Zheyu Ma <zheyuma97@gmail.com>
    Link: https://lore.kernel.org/r/20220410114814.3920474-1-zheyuma97@gmail.com
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    drivers/tty/synclink_gt.c | 2 ++
    1 file changed, 2 insertions(+)

    diff --git a/drivers/tty/synclink_gt.c b/drivers/tty/synclink_gt.c
    index 25c558e65ece..9bc2a9265277 100644
    --- a/drivers/tty/synclink_gt.c
    +++ b/drivers/tty/synclink_gt.c
    @@ -1746,6 +1746,8 @@ static int hdlcdev_init(struct slgt_info *info)
    */
    static void hdlcdev_exit(struct slgt_info *info)
    {
    + if (!info->netdev)
    + return;
    unregister_hdlc_device(info->netdev);
    free_netdev(info->netdev);
    info->netdev = NULL;
    --
    2.35.1


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