Re: [iwl-next,v3] ixgbe: fix unaligned u32 access in ixgbe_update_flash_X550()

[Simon Horman <horms@kernel.org>]

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---
ixgbe: fix unaligned u32 access in ixgbe_update_flash_X550()

This commit adds a u32 member to union ixgbe_hic_hdr2 to ensure 4-byte
alignment on the stack, preventing unaligned 32-bit accesses when
ixgbe_host_interface_command() treats the buffer as a u32 array.

> ixgbe: fix unaligned u32 access in ixgbe_update_flash_X550()
>
> ixgbe_host_interface_command() treats its buffer as a u32 array. The
> local buffer we pass in was a union of byte-sized fields, which gives
> it 1-byte alignment on the stack. On strict-align architectures this
> can cause unaligned 32-bit accesses.
>
> Add a u32 member to union ixgbe_hic_hdr2 so the object is 4-byte
> aligned, and pass the u32 member when calling
> ixgbe_host_interface_command().
>
> No functional change on x86; prevents unaligned accesses on
> architectures that enforce natural alignment.
>
> Fixes: 49425dfc7451 ("ixgbe: Add support for x550em_a 10G MAC type")

Does this Fixes tag point to the correct commit? The alignment issue
appears to have been introduced by commit 6a14ee0cfb19 ("ixgbe: Add X550
support function pointers") from 2014-12-05, which introduced both the
union ixgbe_hic_hdr2 without a u32 member for proper alignment and the
ixgbe_update_flash_X550() function that passes this buffer to
ixgbe_host_interface_command().

Commit 49425dfc7451 from 2016-04-01 only added support for the x550em_a
MAC type and did not introduce the alignment bug.

Should the Fixes tag be:
Fixes: 6a14ee0cfb19 ("ixgbe: Add X550 support function pointers")

> diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_type.h b/drivers/net/ethernet/intel/ixgbe/ixgbe_type.h
> index 61f2ef67defd..eb5bf3b6bbb5 100644
> --- a/drivers/net/ethernet/intel/ixgbe/ixgbe_type.h
> +++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_type.h
> @@ -2798,6 +2798,7 @@ struct ixgbe_hic_hdr2_rsp {
>  };
>
>  union ixgbe_hic_hdr2 {
> +	u32 buf[1];
>  	struct ixgbe_hic_hdr2_req req;
>  	struct ixgbe_hic_hdr2_rsp rsp;
>  };

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