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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id n189sm14973604pfn.108.2020.06.15.12.32.49 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 15 Jun 2020 12:32:50 -0700 (PDT) Date: Mon, 15 Jun 2020 12:32:49 -0700 From: Kees Cook To: Nick Desaulniers Cc: LKML , Linus Torvalds , Miguel Ojeda , Alexander Potapenko , Joe Perches , Andy Whitcroft , "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" , drbd-dev@lists.linbit.com, linux-block@vger.kernel.org, b43-dev@lists.infradead.org, Network Development , linux-wireless , linux-ide@vger.kernel.org, linux-clk@vger.kernel.org, linux-spi@vger.kernel.org, Linux Memory Management List , clang-built-linux , Sebastian Andrzej Siewior , Saravana Kannan Subject: Re: [PATCH 05/10] ide: Remove uninitialized_var() usage Message-ID: <202006151231.74D2315450@keescook> References: <20200603233203.1695403-1-keescook@chromium.org> <20200603233203.1695403-6-keescook@chromium.org> <202006041318.B0EA9059C7@keescook> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: 143C0181BFBC9 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam03 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, Jun 04, 2020 at 01:29:44PM -0700, Nick Desaulniers wrote: > On Thu, Jun 4, 2020 at 1:20 PM Kees Cook wrote: > > > > On Thu, Jun 04, 2020 at 12:29:17PM -0700, Nick Desaulniers wrote: > > > On Wed, Jun 3, 2020 at 4:32 PM Kees Cook 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 remove this variable since it was > > > > actually unused: > > > > > > > > drivers/ide/ide-taskfile.c:232:34: warning: unused variable 'flags' [-Wunused-variable] > > > > unsigned long uninitialized_var(flags); > > > > ^ > > > > > > > > [1] https://lore.kernel.org/lkml/20200603174714.192027-1-glider@google.com/ > > > > [2] https://lore.kernel.org/lkml/CA+55aFw+Vbj0i=1TGqCR5vQkCzWJ0QxK6CernOU6eedsudAixw@mail.gmail.com/ > > > > [3] https://lore.kernel.org/lkml/CA+55aFwgbgqhbp1fkxvRKEpzyR5J8n1vKT1VZdz9knmPuXhOeg@mail.gmail.com/ > > > > [4] https://lore.kernel.org/lkml/CA+55aFz2500WfbKXAx8s67wrm9=yVJu65TpLgN_ybYNv0VEOKA@mail.gmail.com/ > > > > > > > > Signed-off-by: Kees Cook > > > > > > Reviewed-by: Nick Desaulniers > > > > Thanks for the reviews! > > > > > Fixes ce1e518190ea ("ide: don't disable interrupts during kmap_atomic()") > > > > I originally avoided adding Fixes tags because I didn't want these > > changes backported into a -stable without -Wmaybe-uninitialized > > disabled, but in these cases (variable removal), that actually does make > > sense. Thanks! > > Saravana showed me a cool trick for quickly finding commits that > removed a particular identifier that I find faster than `git blame` or > vim-fugitive for the purpose of Fixes tags: > $ git log -S Ah yes, I always have to look up "-S". Good reminder! > I've added it to our wiki: > https://github.com/ClangBuiltLinux/linux/wiki/Command-line-tips-and-tricks#for-finding-which-commit-may-have-removed-a-string-try. > I should update the first tip; what was your suggestion for > constraining the search to the current remote? Ah cool. I've updated it now. It was really to narrow to a "known set of tags", and Linus's tree's tags always start with "v". -- Kees Cook