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Biederman" To: Avi Weiss Cc: Oleg Nesterov , Andrew Morton , Christian Brauner , linux-kernel@vger.kernel.org In-Reply-To: <20261020181101.1605736-1-thnkslprpt@gmail.com> (Avi Weiss's message of "Tue, 20 Oct 2026 21:11:01 +0300") References: <20261020181101.1605736-1-thnkslprpt@gmail.com> Date: Thu, 22 Oct 2026 03:55:36 +0000 Message-ID: <87tsmeo0cn.fsf@email.froward.int.ebiederm.org> User-Agent: Gnus/5.13 (Gnus v5.13) X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain X-XM-SPF: eid=1xJju4-00DfKJ-OZ;;;mid=<87tsmeo0cn.fsf@email.froward.int.ebiederm.org>;;;hst=in02.mta.xmission.com;;;ip=72.198.196.98;;;frm=ebiederm@xmission.com;;;sPfnum=0;;;sPf=pass X-XM-AID: U2FsdGVkX19yqlNQ3wSnFfMwg77E5IpmHQTbBD+J4eg= X-Spam-Level: X-Spam-Virus: No X-Spam-Report: * -1.0 ALL_TRUSTED Passed through trusted hosts only via SMTP * 0.1 BAYES_50 BODY: Bayes spam probability is 40 to 60% * [score: 0.4996] * 0.7 XMSubLong Long Subject * 0.0 T_TM2_M_HEADER_IN_MSG BODY: No description available. * -0.0 DCC_CHECK_NEGATIVE Not listed in DCC * [sa03 1397; Body=1 Fuz1=1 Fuz2=1] * 0.0 T_TooManySym_02 5+ unique symbols in subject * 0.0 T_TooManySym_01 4+ unique symbols in subject X-Spam-DCC: XMission; sa03 1397; Body=1 Fuz1=1 Fuz2=1 X-Spam-Combo: ;Avi Weiss X-Spam-Relay-Country: X-Spam-Timing: total 414 ms - load_scoreonly_sql: 0.06 (0.0%), signal_user_changed: 4.5 (1.1%), b_tie_ro: 2.8 (0.7%), parse: 1.08 (0.3%), extract_message_metadata: 3.8 (0.9%), get_uri_detail_list: 1.41 (0.3%), tests_pri_-2000: 3.7 (0.9%), tests_pri_-1000: 2.5 (0.6%), tests_pri_-950: 1.12 (0.3%), tests_pri_-900: 0.76 (0.2%), tests_pri_-90: 57 (13.8%), check_bayes: 56 (13.5%), b_tokenize: 7 (1.7%), b_tok_get_all: 7 (1.7%), b_comp_prob: 2.4 (0.6%), b_tok_touch_all: 35 (8.4%), b_finish: 1.03 (0.2%), tests_pri_0: 318 (76.8%), check_dkim_signature: 0.66 (0.2%), check_dkim_adsp: 3.6 (0.9%), poll_dns_idle: 1.62 (0.4%), tests_pri_10: 2.1 (0.5%), tests_pri_500: 11 (2.6%), rewrite_mail: 0.00 (0.0%) Subject: Re: [PATCH] signal: skip blocked signals in dequeue_synchronous_signal() X-SA-Exim-Connect-IP: 166.70.13.52 X-SA-Exim-Rcpt-To: linux-kernel@vger.kernel.org, brauner@kernel.org, akpm@linux-foundation.org, oleg@redhat.com, thnkslprpt@gmail.com X-SA-Exim-Mail-From: ebiederm@xmission.com X-SA-Exim-Scanned: No (on out02.mta.xmission.com); SAEximRunCond expanded to false Avi Weiss writes: > dequeue_synchronous_signal() checks whether an unblocked > synchronous signal is pending, but its queue scan can select a > different blocked entry with a positive si_code. This can deliver > a signal while it is still blocked. > > Check the blocked mask for each queued entry. Forced faults > are unblocked when necessary by force_sig_info_to_task(), and the > existing pending bookkeeping is unchanged. I am going to quibble a little with your description. What you describe above as a forced fault, is what the code calls a synchronous signal. As such synchronous signals by definition can not be blocked. Unfortunately the code does not currently have a way to distinguish between such a signal number used synchronously, and such a signal number used normally. Given the poor state of delivering these things I think the code change is technically correct. The comments change is wrong as there is no such thing as a blocked synchronous signal. Eric > Fixes: 7146db3317c6 ("signal: Better detection of synchronous signals") > Signed-off-by: Avi Weiss > --- > > Reproduced by blocking SIGSEGV, queuing a positive-code SIGSEGV > with rt_tgsigqueueinfo(), then triggering an unblocked SIGTRAP. > Without the fix, SIGSEGV was delivered while still blocked. > > Patched version behaved as expected. > > kernel/signal.c | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > > diff --git a/kernel/signal.c b/kernel/signal.c > index e433de93b430..4dcc47a7d30d 100644 > --- a/kernel/signal.c > +++ b/kernel/signal.c > @@ -684,12 +684,13 @@ static int dequeue_synchronous_signal(kernel_siginfo_t *info) > return 0; > > /* > - * Return the first synchronous signal in the queue. > + * Return the first unblocked synchronous signal in the queue. > */ > list_for_each_entry(q, &pending->list, list) { > /* Synchronous signals have a positive si_code */ > if ((q->info.si_code > SI_USER) && > - (sigmask(q->info.si_signo) & SYNCHRONOUS_MASK)) { > + (sigmask(q->info.si_signo) & SYNCHRONOUS_MASK) && > + !sigismember(&tsk->blocked, q->info.si_signo)) { > sync = q; > goto next; > } > > base-commit: f47d223627f80cb7a1eb14c585fe6cb35de5e984