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SubjectRe: [PATCH][next] hfsplus: Fix out-of-bounds warnings in __hfsplus_setxattr
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On 3/30/21 23:53, Matthew Wilcox wrote:
> On Tue, Mar 30, 2021 at 09:43:20PM -0700, Andrew Morton wrote:
>> On Tue, 30 Mar 2021 09:52:26 -0500 "Gustavo A. R. Silva" <gustavoars@kernel.org> wrote:
>>
>>> Fix the following out-of-bounds warnings by enclosing
>>> structure members file and finder into new struct info:
>>>
>>> fs/hfsplus/xattr.c:300:5: warning: 'memcpy' offset [65, 80] from the object at 'entry' is out of the bounds of referenced subobject 'user_info' with type 'struct DInfo' at offset 48 [-Warray-bounds]
>>> fs/hfsplus/xattr.c:313:5: warning: 'memcpy' offset [65, 80] from the object at 'entry' is out of the bounds of referenced subobject 'user_info' with type 'struct FInfo' at offset 48 [-Warray-bounds]
>>>
>>> Refactor the code by making it more "structured."
>>>
>>> Also, this helps with the ongoing efforts to enable -Warray-bounds and
>>> makes the code clearer and avoid confusing the compiler.
>>
>> Confused. What was wrong with the old code? Was this warning
>> legitimate and if so, why? Or is this patch a workaround for a
>> compiler shortcoming?
>
> The offending line is this:
>
> - memcpy(&entry.file.user_info, value,
> + memcpy(&entry.file.info, value,
> file_finderinfo_len);
>
> what it's trying to do is copy two structs which are adjacent to each
> other in a single call to memcpy(). gcc legitimately complains that the
> memcpy to this struct overruns the bounds of the struct. What Gustavo
> has done here is introduce a new struct that contains the two structs,
> and now gcc is happy that the memcpy doesn't overrun the length of this
> containing struct.

Thanks for this, Matthew. :)

--
Gustavo

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