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    Subject[PATCH AUTOSEL 5.12 43/80] media: bt8xx: Fix a missing check bug in bt878_probe
    Date
    From: Zheyu Ma <zheyuma97@gmail.com>

    [ Upstream commit 1a4520090681853e6b850cbe54b27247a013e0e5 ]

    In 'bt878_irq', the driver calls 'tasklet_schedule', but this tasklet is
    set in 'dvb_bt8xx_load_card' of another driver 'dvb-bt8xx'.
    However, this two drivers are separate. The user may not load the
    'dvb-bt8xx' driver when loading the 'bt8xx' driver, that is, the tasklet
    has not been initialized when 'tasklet_schedule' is called, so it is
    necessary to check whether the tasklet is initialized in 'bt878_probe'.

    Fix this by adding a check at the end of bt878_probe.

    The KASAN's report reveals it:

    BUG: unable to handle kernel NULL pointer dereference at 0000000000000000
    PGD 800000006aab2067 P4D 800000006aab2067 PUD 6b2ea067 PMD 0
    Oops: 0010 [#1] PREEMPT SMP KASAN PTI
    CPU: 2 PID: 8724 Comm: syz-executor.0 Not tainted 4.19.177-
    gdba4159c14ef-dirty #40
    Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.0-59-
    gc9ba5276e321-prebuilt.qemu.org 04/01/2014
    RIP: 0010: (null)
    Code: Bad RIP value.
    RSP: 0018:ffff88806c287ea0 EFLAGS: 00010246
    RAX: fffffbfff1b01774 RBX: dffffc0000000000 RCX: 0000000000000000
    RDX: 0000000000000000 RSI: 1ffffffff1b01775 RDI: 0000000000000000
    RBP: ffff88806c287f00 R08: fffffbfff1b01774 R09: fffffbfff1b01774
    R10: 0000000000000001 R11: fffffbfff1b01773 R12: 0000000000000000
    R13: ffff88806c29f530 R14: ffffffff8d80bb88 R15: ffffffff8d80bb90
    FS: 00007f6b550e6700(0000) GS:ffff88806c280000(0000) knlGS:
    0000000000000000
    CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
    CR2: ffffffffffffffd6 CR3: 000000005ec98000 CR4: 00000000000006e0
    DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
    DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
    Call Trace:
    <IRQ>
    tasklet_action_common.isra.17+0x141/0x420 kernel/softirq.c:522
    tasklet_action+0x50/0x70 kernel/softirq.c:540
    __do_softirq+0x224/0x92c kernel/softirq.c:292
    invoke_softirq kernel/softirq.c:372 [inline]
    irq_exit+0x15a/0x180 kernel/softirq.c:412
    exiting_irq arch/x86/include/asm/apic.h:535 [inline]
    do_IRQ+0x123/0x1e0 arch/x86/kernel/irq.c:260
    common_interrupt+0xf/0xf arch/x86/entry/entry_64.S:670
    </IRQ>
    RIP: 0010:__do_sys_interrupt kernel/sys.c:2593 [inline]
    RIP: 0010:__se_sys_interrupt kernel/sys.c:2584 [inline]
    RIP: 0010:__x64_sys_interrupt+0x5b/0x80 kernel/sys.c:2584
    Code: ba 00 04 00 00 48 c7 c7 c0 99 31 8c e8 ae 76 5e 01 48 85 c0 75 21 e8
    14 ae 24 00 48 c7 c3 c0 99 31 8c b8 0c 00 00 00 0f 01 c1 <31> db e8 fe ad
    24 00 48 89 d8 5b 5d c3 48 c7 c3 ea ff ff ff eb ec
    RSP: 0018:ffff888054167f10 EFLAGS: 00000212 ORIG_RAX: ffffffffffffffde
    RAX: 000000000000000c RBX: ffffffff8c3199c0 RCX: ffffc90001ca6000
    RDX: 000000000000001a RSI: ffffffff813478fc RDI: ffffffff8c319dc0
    RBP: ffff888054167f18 R08: 0000000000000000 R09: 0000000000000000
    R10: 0000000000000080 R11: fffffbfff18633b7 R12: ffff888054167f58
    R13: ffff88805f638000 R14: 0000000000000000 R15: 0000000000000000
    do_syscall_64+0xb0/0x4e0 arch/x86/entry/common.c:293
    entry_SYSCALL_64_after_hwframe+0x49/0xbe
    RIP: 0033:0x4692a9
    Code: f7 d8 64 89 02 b8 ff ff ff ff c3 66 0f 1f 44 00 00 48 89 f8 48 89 f7
    48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff
    ff 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48
    RSP: 002b:00007f6b550e5c48 EFLAGS: 00000246 ORIG_RAX: 000000000000014f
    RAX: ffffffffffffffda RBX: 000000000077bf60 RCX: 00000000004692a9
    RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000020000140
    RBP: 00000000004cf7eb R08: 0000000000000000 R09: 0000000000000000
    R10: 0000000000000000 R11: 0000000000000246 R12: 000000000077bf60
    R13: 0000000000000000 R14: 000000000077bf60 R15: 00007fff55a1dca0
    Modules linked in:
    Dumping ftrace buffer:
    (ftrace buffer empty)
    CR2: 0000000000000000
    ---[ end trace 68e5849c3f77cbb6 ]---
    RIP: 0010: (null)
    Code: Bad RIP value.
    RSP: 0018:ffff88806c287ea0 EFLAGS: 00010246
    RAX: fffffbfff1b01774 RBX: dffffc0000000000 RCX: 0000000000000000
    RDX: 0000000000000000 RSI: 1ffffffff1b01775 RDI: 0000000000000000
    RBP: ffff88806c287f00 R08: fffffbfff1b01774 R09: fffffbfff1b01774
    R10: 0000000000000001 R11: fffffbfff1b01773 R12: 0000000000000000
    R13: ffff88806c29f530 R14: ffffffff8d80bb88 R15: ffffffff8d80bb90
    FS: 00007f6b550e6700(0000) GS:ffff88806c280000(0000) knlGS:
    0000000000000000
    CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
    CR2: ffffffffffffffd6 CR3: 000000005ec98000 CR4: 00000000000006e0
    DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
    DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400

    Reported-by: Zheyu Ma <zheyuma97@gmail.com>
    Signed-off-by: Zheyu Ma <zheyuma97@gmail.com>
    Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
    Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    drivers/media/pci/bt8xx/bt878.c | 3 +++
    1 file changed, 3 insertions(+)

    diff --git a/drivers/media/pci/bt8xx/bt878.c b/drivers/media/pci/bt8xx/bt878.c
    index 7ca309121fb5..90972d6952f1 100644
    --- a/drivers/media/pci/bt8xx/bt878.c
    +++ b/drivers/media/pci/bt8xx/bt878.c
    @@ -478,6 +478,9 @@ static int bt878_probe(struct pci_dev *dev, const struct pci_device_id *pci_id)
    btwrite(0, BT878_AINT_MASK);
    bt878_num++;

    + if (!bt->tasklet.func)
    + tasklet_disable(&bt->tasklet);
    +
    return 0;

    fail2:
    --
    2.30.2
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