On Thu, Jul 29, 2021 at 12:45:47PM +0200, David Sterba wrote:

On Wed, Jul 28, 2021 at 02:54:52PM -0700, Kees Cook wrote:

quoted

On Wed, Jul 28, 2021 at 11:23:23AM +0200, David Sterba wrote:

quoted

On Wed, Jul 28, 2021 at 10:35:56AM +0300, Dan Carpenter wrote:

quoted

@@ -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.

Ah, good catch! I think just using BIT() is the right replacement here,
yes? I suppose that should be a separate patch.

I found definition of BIT in vdso/bits.h, that does not sound like a
standard header, besides that it shifts 1UL, that may not be necessary
everywhere. IIRC there were objections against using the macro at all.

3945ff37d2f4 ("linux/bits.h: Extract common header for vDSO") moved it
there from linux/bits.h, and linux/bits.h now includes vdso/bits.h, so
it is still ever-present. :)

-- 
Kees Cook