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Message-ID: <CAA-b7a8v8q5VnPxWw+o6Vj96KxeVhgfmZbre8+9rLRcB7-emyg@mail.gmail.com> Date: Sun, 29 May 2016 23:50:18 -0700 From: Kirtika Ruchandani <kirtika.ruchandani@...il.com> To: Julian Calaby <julian.calaby@...il.com> Cc: Johannes Berg <johannes@...solutions.net>, linux-wireless <linux-wireless@...r.kernel.org>, Tina Ruchandani <ruchandani.tina@...il.com>, netdev <netdev@...r.kernel.org> Subject: Re: [PATCH v2 03/10] nl80211: Prefer ether_addr_copy > This looks right to me, but doesn't ether_addr_copy() have alignment > requirements? Could someone more familiar with that review these > changes to ensure they're met? Thanks for catching this. The requirement is to be __aligned(2). I've added 4 instances of ether_addr_copy with 8 addresses as arguments. Of these, the 4 src arguments are really the same type (i.e. nla_data acting on a const nlattr*), so I'll try to reason about the 5 total cases below - 1. cfg->dst_mac should be 16-bit aligned due to the layout of struct cfg80211_wowlan_tcp. Its offset is 10 or 12 bytes in the structure depending on the system. 2 and 3. For mac_addr and mac_addr_mask, nl80211_parse_random_mac takes these in as u8* (and hence does not guarantee alignment?) Both the callers of this function today pass in arguments that are explicitly __aligned(2). But this cannot be said of future potential callers - so perhaps my patch introduces a bug? 4. Based on struct cfg80211_acl_data, acl->mac_addrs[i] should be not guaranteed to be __aligned(2). 5. For all the nla_data src arguments, the nla_data function returns ((char*) foo + 5) for pointer foo. So likely not __aligned(2). Based on 3, 4 and 5, this patch should be revoked, but it would be nice to have a confirmation from someone else.
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