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Date:   Thu, 9 Sep 2021 15:26:43 -0700
From:   John Hubbard <>
To:     Andrew Morton <>,
        Kees Cook <>
Cc:     kernel test robot <>,
        Matt Porter <>,
        Alexandre Bounine <>,
        Jing Xiangfeng <>,
        Ira Weiny <>,
        Souptick Joarder <>,
        "Gustavo A . R . Silva" <>,
        Dan Carpenter <>,,
Subject: Re: [PATCH] rapidio: Avoid bogus __alloc_size warning

On 9/9/21 13:27, Andrew Morton wrote:
>>     include/linux/thread_info.h:213:4: error: call to '__bad_copy_to' declared with attribute error: copy destination size is too small
>>       213 |    __bad_copy_to();
>>           |    ^~~~~~~~~~~~~~~
>> But the allocation size and the copy size are identical:
>> 	transfer = vmalloc(array_size(sizeof(*transfer), transaction.count));
>> 	if (!transfer)
>> 		return -ENOMEM;
>> 	if (unlikely(copy_from_user(transfer,
>> 				    (void __user *)(uintptr_t)transaction.block,
>> 				    array_size(sizeof(*transfer), transaction.count)))) {
> That's an "error", not a warning.  Or is this thanks to the new -Werror?
> Either way, I'm inclined to cc:stable on this, because use of gcc-9 on
> older kernels will be a common thing down the ages.
> If it's really an "error" on non-Werror kernels then definitely cc:stable.

It looks like a hard error, not a warning upgraded by -Werror: I did a local
repro, then ran with V=1, removed all -Werror parts of the gcc invocation,
ran again, and still reproduced the error.

I also verified that the patch causes the error to go away.

Also, I can't find anything wrong with the diffs, so:

Reviewed-by: John Hubbard <>

John Hubbard

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