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SubjectRe: [PATCH] spi: bitbang: Fix NULL pointer dereference in spi_unregister_master
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On 5/16/2019 1:26 PM, YueHaibing wrote:
> If spi_register_master fails in spi_bitbang_start
> because device_add failure, We should return the
> error code other than 0, otherwise calling
> spi_bitbang_stop may trigger NULL pointer dereference
> like this:
>
> BUG: KASAN: null-ptr-deref in __list_del_entry_valid+0x45/0xd0
> Read of size 8 at addr 0000000000000000 by task syz-executor.0/3661
>
> CPU: 0 PID: 3661 Comm: syz-executor.0 Not tainted 5.1.0+ #28
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1ubuntu1 04/01/2014
> Call Trace:
> dump_stack+0xa9/0x10e
> ? __list_del_entry_valid+0x45/0xd0
> ? __list_del_entry_valid+0x45/0xd0
> __kasan_report+0x171/0x18d
> ? __list_del_entry_valid+0x45/0xd0
> kasan_report+0xe/0x20
> __list_del_entry_valid+0x45/0xd0
> spi_unregister_controller+0x99/0x1b0
> spi_lm70llp_attach+0x3ae/0x4b0 [spi_lm70llp]
> ? 0xffffffffc1128000
> ? klist_next+0x131/0x1e0
> ? driver_detach+0x40/0x40 [parport]
> port_check+0x3b/0x50 [parport]
> bus_for_each_dev+0x115/0x180
> ? subsys_dev_iter_exit+0x20/0x20
> __parport_register_driver+0x1f0/0x210 [parport]
> ? 0xffffffffc1150000
> do_one_initcall+0xb9/0x3b5
> ? perf_trace_initcall_level+0x270/0x270
> ? kasan_unpoison_shadow+0x30/0x40
> ? kasan_unpoison_shadow+0x30/0x40
> do_init_module+0xe0/0x330
> load_module+0x38eb/0x4270
> ? module_frob_arch_sections+0x20/0x20
> ? kernel_read_file+0x188/0x3f0
> ? find_held_lock+0x6d/0xd0
> ? fput_many+0x1a/0xe0
> ? __do_sys_finit_module+0x162/0x190
> __do_sys_finit_module+0x162/0x190
> ? __ia32_sys_init_module+0x40/0x40
> ? __mutex_unlock_slowpath+0xb4/0x3f0
> ? wait_for_completion+0x240/0x240
> ? vfs_write+0x160/0x2a0
> ? lockdep_hardirqs_off+0xb5/0x100
> ? mark_held_locks+0x1a/0x90
> ? do_syscall_64+0x14/0x2a0
> do_syscall_64+0x72/0x2a0
> entry_SYSCALL_64_after_hwframe+0x49/0xbe
>
> Reported-by: Hulk Robot <hulkci@huawei.com>
> Fixes: 702a4879ec33 ("spi: bitbang: Let spi_bitbang_start() take a reference to master")
> Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Reviewed-by: Mukesh Ojha <mojha@codeaurora.org>

Cheers,
-Mukesh

> ---
> drivers/spi/spi-bitbang.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/spi/spi-bitbang.c b/drivers/spi/spi-bitbang.c
> index dd9a8c54..be95be4 100644
> --- a/drivers/spi/spi-bitbang.c
> +++ b/drivers/spi/spi-bitbang.c
> @@ -403,7 +403,7 @@ int spi_bitbang_start(struct spi_bitbang *bitbang)
> if (ret)
> spi_master_put(master);
>
> - return 0;
> + return ret;
> }
> EXPORT_SYMBOL_GPL(spi_bitbang_start);
>

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