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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> |
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Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.