On April 12, 2017 6:52 AM Mike Kravetz wrote:
>
> If mmap() maps a file, it can be passed an offset into the file at
> which the mapping is to start. Offset could be a negative value when
> represented as a loff_t. The offset plus length will be used to
> update the file size (i_size) which is also a loff_t. Validate the
> value of offset and offset + length to make sure they do not overflow
> and appear as negative.
>
> Found by syzcaller with commit ff8c0c53c475 ("mm/hugetlb.c: don't call
> region_abort if region_chg fails") applied. Prior to this commit, the
> overflow would still occur but we would luckily return ENOMEM.
> To reproduce:
> mmap(0, 0x2000, 0, 0x40021, 0xffffffffffffffffULL, 0x8000000000000000ULL);
>
> Resulted in,
> kernel BUG at mm/hugetlb.c:742!
> Call Trace:
> hugetlbfs_evict_inode+0x80/0xa0
> ? hugetlbfs_setattr+0x3c0/0x3c0
> evict+0x24a/0x620
> iput+0x48f/0x8c0
> dentry_unlink_inode+0x31f/0x4d0
> __dentry_kill+0x292/0x5e0
> dput+0x730/0x830
> __fput+0x438/0x720
> ____fput+0x1a/0x20
> task_work_run+0xfe/0x180
> exit_to_usermode_loop+0x133/0x150
> syscall_return_slowpath+0x184/0x1c0
> entry_SYSCALL_64_fastpath+0xab/0xad
>
> Reported-by: Vegard Nossum <vegard.nossum@xxxxxxxxx>
> Signed-off-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
> ---
Acked-by: Hillf Danton <hillf.zj@xxxxxxxxxxxxxxx>
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