On Wed, Jun 3, 2020 at 4:32 PM Kees Cook <keescook@xxxxxxxxxxxx> wrote: > > Using uninitialized_var() is dangerous as it papers over real bugs[1] > (or can in the future), and suppresses unrelated compiler warnings (e.g. > "unused variable"). If the compiler thinks it is uninitialized, either > simply initialize the variable or make compiler changes. As a precursor > to removing[2] this[3] macro[4], just initialize this variable to NULL, > and make the (unreachable!) code do a conditional test. > > [1] https://lore.kernel.org/lkml/20200603174714.192027-1-glider@xxxxxxxxxx/ > [2] https://lore.kernel.org/lkml/CA+55aFw+Vbj0i=1TGqCR5vQkCzWJ0QxK6CernOU6eedsudAixw@xxxxxxxxxxxxxx/ > [3] https://lore.kernel.org/lkml/CA+55aFwgbgqhbp1fkxvRKEpzyR5J8n1vKT1VZdz9knmPuXhOeg@xxxxxxxxxxxxxx/ > [4] https://lore.kernel.org/lkml/CA+55aFz2500WfbKXAx8s67wrm9=yVJu65TpLgN_ybYNv0VEOKA@xxxxxxxxxxxxxx/ > > Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx> > --- > drivers/net/wireless/broadcom/b43/phy_n.c | 10 +++++++--- > 1 file changed, 7 insertions(+), 3 deletions(-) > > diff --git a/drivers/net/wireless/broadcom/b43/phy_n.c b/drivers/net/wireless/broadcom/b43/phy_n.c > index d3c001fa8eb4..88cdcea10d61 100644 > --- a/drivers/net/wireless/broadcom/b43/phy_n.c > +++ b/drivers/net/wireless/broadcom/b43/phy_n.c > @@ -4222,7 +4222,7 @@ static void b43_nphy_tx_gain_table_upload(struct b43_wldev *dev) The TODOs and `#if 0` in this function are concerning. It looks like `rf_pwr_offset_table` is only used when `phy->rev` is >=7 && < 19. Further, the loop has a case for `phy->rev >= 19` but we would have returned earlier if that was the case. > u32 rfpwr_offset; > u8 pga_gain, pad_gain; > int i; > - const s16 *uninitialized_var(rf_pwr_offset_table); > + const s16 *rf_pwr_offset_table = NULL; > > table = b43_nphy_get_tx_gain_table(dev); > if (!table) > @@ -4256,9 +4256,13 @@ static void b43_nphy_tx_gain_table_upload(struct b43_wldev *dev) > pga_gain = (table[i] >> 24) & 0xf; > pad_gain = (table[i] >> 19) & 0x1f; > if (b43_current_band(dev->wl) == NL80211_BAND_2GHZ) > - rfpwr_offset = rf_pwr_offset_table[pad_gain]; > + rfpwr_offset = rf_pwr_offset_table > + ? rf_pwr_offset_table[pad_gain] > + : 0; > else > - rfpwr_offset = rf_pwr_offset_table[pga_gain]; > + rfpwr_offset = rf_pwr_offset_table > + ? rf_pwr_offset_table[pga_gain] > + : 0; The code is trying to check `phy->rev >= 7 && phy->rev < 19` once before the loop, then set `rf_pwr_offset_table`, so having another conditional on `rf_pwr_offset_table` in the loop is unnecessary. I'm ok with initializing it to `NULL`, but I'm not sure the conditional check is necessary. Do you get a compiler warning otherwise? > } else { > pga_gain = (table[i] >> 24) & 0xF; > if (b43_current_band(dev->wl) == NL80211_BAND_2GHZ) > -- > 2.25.1 > > -- > You received this message because you are subscribed to the Google Groups "Clang Built Linux" group. > To unsubscribe from this group and stop receiving emails from it, send an email to clang-built-linux+unsubscribe@xxxxxxxxxxxxxxxx. > To view this discussion on the web visit https://groups.google.com/d/msgid/clang-built-linux/20200603233203.1695403-4-keescook%40chromium.org. -- Thanks, ~Nick Desaulniers
