On Mon, 2019-11-04 at 09:37 -0800, coverity-bot wrote: > Hello! > > This is an experimental automated report about issues detected by Coverity > from a scan of next-20191031 as part of the linux-next weekly scan project: > https://scan.coverity.com/projects/linux-next-weekly-scan > > You're getting this email because you were associated with the identified > lines of code (noted below) that were touched by recent commits: > > 14124b25780d ("iwlwifi: dbg_ini: implement monitor allocation flow") > > Coverity reported the following: > > *** CID 1487402: Control flow issues (DEADCODE) > /drivers/net/wireless/intel/iwlwifi/iwl-dbg-tlv.c: 497 in iwl_dbg_tlv_alloc_fragment() > 491 pages * PAGE_SIZE); > 492 > 493 pages = DIV_ROUND_UP(pages, 2); > 494 } > 495 > 496 if (!block) > vvv CID 1487402: Control flow issues (DEADCODE) > vvv Execution cannot reach this statement: "return -12;". > 497 return -ENOMEM; > 498 > 499 frag->physical = physical; > 500 frag->block = block; > 501 frag->size = pages * PAGE_SIZE; > 502 > > If this is a false positive, please let us know so we can mark it as > such, or teach the Coverity rules to be smarter. If not, please make > sure fixes get into linux-next. :) For patches fixing this, please > include these lines (but double-check the "Fixes" first): > > Reported-by: coverity-bot <keescook+coverity-bot@xxxxxxxxxxxx> > Addresses-Coverity-ID: 1487402 ("Control flow issues") > Fixes: 14124b25780d ("iwlwifi: dbg_ini: implement monitor allocation flow") > > > Thanks for your attention! Hi, This is a good catch! We have a loop: while (pages) { block = dma_alloc_coherent(fwrt->dev, pages * PAGE_SIZE, &physical, GFP_KERNEL | __GFP_NOWARN); if (block) break; IWL_WARN(fwrt, "WRT: Failed to allocate fragment size %lu\n", pages * PAGE_SIZE); pages = DIV_ROUND_UP(pages, 2); } if (!block) return -ENOMEM; Which seems like it will keep trying allocate smaller and smaller blocks until it succeeds. But "pages" will never become zero (because of the DIV_ROUND_UP), so if we can't allocate any size and pages becomes 1, we will keep trying to allocate 1 page until it succeeds. And in that case, as coverity reported, block will never be NULL. I'll add a fix to this in our internal tree and it will reach the mainline following our normal upstream process. -- Cheers, Luca.
