Hi,
This commit fixes a race condition an unprivileged user can exploit to corrupt
kernel memory. I can't seem to get anyone to grab it for the past 4+ months.
Help please?
Thanks,
Sasha
On 04/30/2015 11:04 AM, Sasha Levin wrote:
> ping?
>
> On 01/28/2015 03:30 PM, Sasha Levin wrote:
>> We used to read file_handle twice. Once to get the amount of extra bytes, and
>> once to fetch the entire structure.
>>
>> This may be problematic since we do size verifications only after the first
>> read, so if the number of extra bytes changes in userspace between the first
>> and second calls, we'll have an incoherent view of file_handle.
>>
>> Instead, read the constant size once, and copy that over to the final
>> structure without having to re-read it again.
>>
>> Signed-off-by: Sasha Levin <sasha.levin@xxxxxxxxxx>
>> ---
>> Change in v2:
>> - Use the f_handle pointer rather than size of struct
>>
>> fs/fhandle.c | 5 +++--
>> 1 file changed, 3 insertions(+), 2 deletions(-)
>>
>> diff --git a/fs/fhandle.c b/fs/fhandle.c
>> index 999ff5c..d59712d 100644
>> --- a/fs/fhandle.c
>> +++ b/fs/fhandle.c
>> @@ -195,8 +195,9 @@ static int handle_to_path(int mountdirfd, struct file_handle __user *ufh,
>> goto out_err;
>> }
>> /* copy the full handle */
>> - if (copy_from_user(handle, ufh,
>> - sizeof(struct file_handle) +
>> + *handle = f_handle;
>> + if (copy_from_user(&handle->f_handle,
>> + &ufh->f_handle,
>> f_handle.handle_bytes)) {
>> retval = -EFAULT;
>> goto out_handle;
>>
>
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