Re: [PATCH 02/64] mac80211: Use flex-array for radiotap header bitmap
From: David Sterba <hidden>
Date: 2021-07-28 09:26:14
Also in:
dri-devel, linux-block, linux-hardening, linux-kbuild, linux-staging, linux-wireless, lkml
On Wed, Jul 28, 2021 at 10:35:56AM +0300, Dan Carpenter wrote:
quoted hunk ↗ jump to hunk
@@ -372,7 +372,7 @@ ieee80211_add_rx_radiotap_header(struct ieee80211_local *local, ieee80211_calculate_rx_timestamp(local, status, mpdulen, 0), pos); - rthdr->it_present |= cpu_to_le32(1 << IEEE80211_RADIOTAP_TSFT); + rthdr->data.it_present |= cpu_to_le32(1 << IEEE80211_RADIOTAP_TSFT);
A drive-by comment, not related to the patchset, but rather the ieee80211 driver itself. Shift expressions with (1 << NUMBER) can be subtly broken once the NUMBER is 31 and the value gets silently cast to a 64bit type. It will become 0xfffffffff80000000. I've checked the IEEE80211_RADIOTAP_* defintions if this is even remotely possible and yes, IEEE80211_RADIOTAP_EXT == 31. Fortunatelly it seems to be used with used with a 32bit types (eg. _bitmap_shifter) so there are no surprises. The recommended practice is to always use unsigned types for shifts, so "1U << ..." at least.