[PATCH] erofs: fix NULL dereference of dif->bdev_handle in fscache mode

[Yue Hu]

On Tue, 14 Nov 2023 15:07:04 +0800
Jingbo Xu <jefflexu at linux.alibaba.com> wrote:

> Avoid NULL dereference of dif->bdev_handle, as dif->bdev_handle is NULL
> in fscache mode.
> 
>  BUG: kernel NULL pointer dereference, address: 0000000000000000
>  RIP: 0010:erofs_map_dev+0xbd/0x1c0
>  Call Trace:
>   <TASK>
>   erofs_fscache_data_read_slice+0xa7/0x340
>   erofs_fscache_data_read+0x11/0x30
>   erofs_fscache_readahead+0xd9/0x100
>   read_pages+0x47/0x1f0
>   page_cache_ra_order+0x1e5/0x270
>   filemap_get_pages+0xf2/0x5f0
>   filemap_read+0xb8/0x2e0
>   vfs_read+0x18d/0x2b0
>   ksys_read+0x53/0xd0
>   do_syscall_64+0x42/0xf0
>   entry_SYSCALL_64_after_hwframe+0x6e/0x76
> 
> Reported-by: Yiqun Leng <yqleng at linux.alibaba.com>
> Closes: https://bugzilla.openanolis.cn/show_bug.cgi?id=7245
> Fixes: 49845720080d ("erofs: Convert to use bdev_open_by_path()")
> Signed-off-by: Jingbo Xu <jefflexu at linux.alibaba.com>

Reviewed-by: Yue Hu <huyue2 at coolpad.com>