On Mon, Oct 09, 2017 at 11:15:40PM +0000, Levin, Alexander (Sasha Levin) wrote: > On Mon, Oct 09, 2017 at 04:06:20PM -0700, Alexei Starovoitov wrote: > >On Mon, Oct 09, 2017 at 08:26:34PM +0000, Levin, Alexander (Sasha Levin) > >wrote: > >> On Mon, Oct 09, 2017 at 10:15:42AM -0700, Alexei Starovoitov wrote: > >> >On Mon, Oct 09, 2017 at 11:37:59AM -0400, Tim Hansen wrote: > >> >> Fix BUG() calls to use BUG_ON(conditional) macros. > >> >> > >> >> This was found using make coccicheck M=net/core on linux next > >> >> tag next-2017092 > >> >> > >> >> Signed-off-by: Tim Hansen <devtimhan...@gmail.com> > >> >> --- > >> >> net/core/skbuff.c | 15 ++++++--------- > >> >> 1 file changed, 6 insertions(+), 9 deletions(-) > >> >> > >> >> diff --git a/net/core/skbuff.c b/net/core/skbuff.c > >> >> index d98c2e3ce2bf..34ce4c1a0f3c 100644 > >> >> --- a/net/core/skbuff.c > >> >> +++ b/net/core/skbuff.c > >> >> @@ -1350,8 +1350,7 @@ struct sk_buff *skb_copy(const struct sk_buff > >> >> *skb, gfp_t gfp_mask) > >> >> /* Set the tail pointer and length */ > >> >> skb_put(n, skb->len); > >> >> > >> >> - if (skb_copy_bits(skb, -headerlen, n->head, headerlen + > >> >> skb->len)) > >> >> - BUG(); > >> >> + BUG_ON(skb_copy_bits(skb, -headerlen, n->head, headerlen + > >> >> skb->len)); > >> > > >> >I'm concerned with this change. > >> >1. Calling non-trivial bit of code inside the macro is a poor coding > >> >style (imo) > >> >2. BUG_ON != BUG. Some archs like mips and ppc have HAVE_ARCH_BUG_ON and > >> >implementation > >> >of BUG and BUG_ON look quite different. > >> > >> For these archs, wouldn't it then be more efficient to use BUG_ON rather > >> than BUG()? > > > >why more efficient? any data to prove that? > > Just guessing. > > Either way, is there a particular reason for not using BUG_ON() here > besides that it's implementation is "quite different"? > > >I'm pointing that the change is not equivalent and > >this code has been around forever (pre-git days), so I see > >no reason to risk changing it. > > Do you know that BUG_ON() is broken on any archs? > > If not, "this code has been around forever" is really not an excuse to > not touch code. > > If BUG_ON() behavior is broken somewhere, then it needs to get fixed.
no idea whether it's broken. My main objection is #1. imo it's a very poor coding style to put functions with side-effects into macros. Especially debug/bug/warn-like. For example llvm has DEBUG() macro and everything inside will disappear depending on compilation flags. I wouldn't be surprised if somebody for the name of security (to avoid crash on BUG_ON) will replace BUG/BUG_ON with some other implementation or nop and will have real bugs, since skb_copy_bits() is somehow not called or called in different context.
