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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , skhan@linuxfoundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Kuniyuki Iwashima , linux-sparse@vger.kernel.org Subject: Re: [PATCH net-next v2] af_unix: Fix undefined 'other' error Message-ID: <4fbba9c0-1802-43ec-99c4-e456b38b6ffd@stanley.mountain> References: <20250210075006.9126-1-purvayeshi550@gmail.com> <20250215172440.GS1615191@kernel.org> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250215172440.GS1615191@kernel.org> I've added the linux-sparse@vger.kernel.org mailing list to the CC. On Sat, Feb 15, 2025 at 05:24:40PM +0000, Simon Horman wrote: > My understanding is that the two static analysis tools under discussion > are Smatch and Sparse, where AFAIK Smatch is a fork of Sparse. > > Without this patch, when checking af_unix.c, both Smatch and Sparse report > (only): > > .../af_unix.c:1511:9: error: undefined identifier 'other' > .../af_unix.c:1511:9: error: undefined identifier 'other' > .../af_unix.c:1511:9: error: undefined identifier 'other' > .../af_unix.c:1511:9: error: undefined identifier 'other' > Smatch isn't a fork of Sparse, it uses Sparse as a C front-end. This warning is really from Sparse, not Smatch. The warning started when we changed the definition of unix_sk() in commit b064ba9c3cfa ("af_unix: preserve const qualifier in unix_sk()"). Smatch doesn't actually use these locking annotations at all. Instead, Smatch has a giant table with all the locks listed. https://github.com/error27/smatch/blob/master/smatch_locking.c Smatch uses the cross function database for this as well if it's available. Unfortunately, Smatch does not parse the unix_wait_for_peer() function correctly. It sees that something is unlocked but it can't figure out what. I believe the problem is that Smatch doesn't parse container_of_const(). Fixing that has been on my TODO list for a while. The caller used unix_state_lock() to take the lock and that has a unix_sk() in it as well. So smatch doesn't see this lock at all that's why it doesn't print a warning. regards, dan carpenter > Without this patch, when checking af_unix.c, both Smatch and Sparse report > (only): > > .../af_unix.c:1511:9: error: undefined identifier 'other' > .../af_unix.c:1511:9: error: undefined identifier 'other' > .../af_unix.c:1511:9: error: undefined identifier 'other' > .../af_unix.c:1511:9: error: undefined identifier 'other' > > And with either v1 or v2 of this patch applied Smatch reports nothing. > While Sparse reports: > > .../af_unix.c:234:13: warning: context imbalance in 'unix_table_double_lock' - wrong count at exit > .../af_unix.c:253:28: warning: context imbalance in 'unix_table_double_unlock' - unexpected unlock > .../af_unix.c:1386:13: warning: context imbalance in 'unix_state_double_lock' - wrong count at exit > .../af_unix.c:1403:17: warning: context imbalance in 'unix_state_double_unlock' - unexpected unlock > .../af_unix.c:2089:25: warning: context imbalance in 'unix_dgram_sendmsg' - unexpected unlock > .../af_unix.c:3335:20: warning: context imbalance in 'unix_get_first' - wrong count at exit > .../af_unix.c:3366:34: warning: context imbalance in 'unix_get_next' - unexpected unlock > .../af_unix.c:3396:42: warning: context imbalance in 'unix_seq_stop' - unexpected unlock > .../af_unix.c:3499:34: warning: context imbalance in 'bpf_iter_unix_hold_batch' - unexpected unlock > > TBH, I'm unsure which is worse. Nor how to improve things.