From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794049164; b=02Z/xNbxPy9UaSMlP4zZrXUhJyrXtqrdR3KdJgPngDrgI0Bv7IQJacvq17lJFvphLQ+3 EaH5ntgZZJ/THgotGJxCBbUhuwOf4zi3ryLXzG9JxFax1WSUJXDx8W2O9hnWC7WD3tUpq cnKzvPGMKhGdYZnSX+itU1V9rhmjG7xVzH47qxB3tpSl96QVrcoxXT0/FD6plPBNyOed2 kZtYHMPNc4mkeU29Am1GKKD3cuzDDzqZKeJsfYryGX27y7WBiETaJ/cVrmiM3tdaldF10 Fhbp5ciBewJQ1xy+7Cr3NLYM1Aox4V/M/+NTGBZhrG/fxWWpiIdaoKQPfuzkw4g5hPQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794049164; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: MIME-Version:Content-Type:Content-Transfer-Encoding; bh=jVAGDxjxZFUaujA2O/JK5dFkRvK+biBXWgj6HlnnWio=; b=CO6aZrAwKFADldJ5EEZOn3ypiExjSshLlmFlqrqqteLak30G+Fwvu356WMd3KnUNI4mw dZ796zmgiW3rh2iKo5/wEaqA5rsjSq/0QB5hoM7z8DmZl4zxt/WfSPOzx3jrNnoaBRI8o 0XUIR7BJYqyTVIpCvVKUHvL5nY7KpT9wD54nVMv0XFS68aRAf2tLL8Ks15NK8CqXI1BrY 3Hz/nWNiqKSKfVZF8PaYDchIosXj3a0n27cvj/qt/v0rPKR4cRYrr9539mpXmSzhUrlPi IxH5U0u1Ad/h9pSBKNUCxVsV8Y/D6rESq4XUMKnMHM7PbPbAE6GuAYFj3ErvFhe7Spg== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=Zsg+7tIG; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B9BA5606A32E for ; Sat, 7 Nov 2026 10:59:23 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=Zsg+7tIG Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1EC101F0089F; Sat, 7 Nov 2026 10:59:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794049163; bh=jVAGDxjxZFUaujA2O/JK5dFkRvK+biBXWgj6HlnnWio=; h=From:To:Cc:Subject:Date; b=Zsg+7tIG3Ai1gMTE0Z7mea+sa8t1usWW0UI+ZNmyHY/rs1EwvF4hO5HI8YjtkDoYF DH3szobS/1AHtzXvs8ImUY2a4NQJM68P0WPR78F6XoGSRBFrj3nQ7RJvDRgW3q9Pok CDNB5dsqKdo7kr6zJxHZlRaG2bCu5TtGyrEkL8tOrrITDfZbDdsDSWj4QIxITs/v7n swqetOnhHCoAO6xI1QG9/tmkNQeW6ikaLjH35L0OGWjXBMr+XmcA9aHOhRju6wM0v1 npm+u9v+bQ9QYrEqd2w8Xzh8rln5kpAsc281QvGcIZldiu2Tzfhqc39CUSX+/cmhgc kFf7AWTT0lSqQ== From: Sasha Levin To: oleg@redhat.com, kusaram@devineni.in, kees@kernel.org Cc: stable@vger.kernel.org Subject: FAILED: patch "[PATCH] signalfd: don't dequeue the forced fatal signals" failed to apply to 5.15-stable tree Date: Sat, 7 Nov 2026 05:59:21 -0500 Message-ID: <20261107055921-failed-5.15-d72e0fb3b00c@kernel.org> X-Mailer: git-send-email 2.53.0 X-Mailing-List: stable@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; charset=UTF-8 Content-Transfer-Encoding: 8bit The patch below does not apply to the 5.15-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y git checkout FETCH_HEAD git cherry-pick -x d72e0fb3b00c6a1146bcfd7186ad9f6f609ba236 # git commit -s git send-email --to '' --in-reply-to '20261107055921-failed-5.15-d72e0fb3b00c@kernel.org' --subject-prefix 'PATCH 5.15.y' 'HEAD^..' Thanks, Sasha ------------------ original commit in Linus's tree ------------------ >From d72e0fb3b00c6a1146bcfd7186ad9f6f609ba236 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Mon, 6 Apr 2026 15:37:32 +0200 Subject: [PATCH] signalfd: don't dequeue the forced fatal signals These signals should act like SIGKILL, in that userspace must never dequeue them. But as Kusaram explains, io_uring-driven signalfd_read_iter() called from get_signal() -> task_work_run() paths can do this before get_signal() has a chance to dequeue such a signal and notice SA_IMMUTABLE. Change signalfd_poll() and signalfd_dequeue() to add pending SA_IMMUTABLE signals to ctx->sigmask. TODO: we should probably change force_sig_info_to_task(HANDLER_EXIT) to make fatal_signal_pending() true, or add a fatal_or_forced_signal_pending() helper. Then signalfd_dequeue() could just return -EINTR in this case. This also makes sense for get_signal(), which could prioritize a fatal signal sent by (say) force_sig_seccomp(force_coredump => true), just like it already prioritizes SIGKILL. Cc: stable@kernel.org Reported-by: syzbot+0a4c46806941297fecb9@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=0a4c46806941297fecb9 Tested-by: syzbot+0a4c46806941297fecb9@syzkaller.appspotmail.com Link: https://lore.kernel.org/all/69d122fd.050a0220.2dbe29.001c.GAE@google.com/ Suggested-by: Kusaram Devineni Signed-off-by: Oleg Nesterov Reviewed-by: Kees Cook Link: https://patch.msgid.link/adO3HG8bvwRPcmte@redhat.com Signed-off-by: Kees Cook --- fs/signalfd.c | 28 ++++++++++++++++++++++------ 1 file changed, 22 insertions(+), 6 deletions(-) diff --git a/fs/signalfd.c b/fs/signalfd.c index dff53745e3524..22bc0870a824d 100644 --- a/fs/signalfd.c +++ b/fs/signalfd.c @@ -48,17 +48,30 @@ static int signalfd_release(struct inode *inode, struct file *file) return 0; } +static void refine_sigmask(struct signalfd_ctx *ctx, sigset_t *sigmask) +{ + struct k_sigaction *k = current->sighand->action; + int n; + + *sigmask = ctx->sigmask; + for (n = 1; n <= _NSIG; ++n, ++k) { + if (k->sa.sa_flags & SA_IMMUTABLE) + sigaddset(sigmask, n); + } +} + static __poll_t signalfd_poll(struct file *file, poll_table *wait) { struct signalfd_ctx *ctx = file->private_data; __poll_t events = 0; + sigset_t sigmask; poll_wait(file, ¤t->sighand->signalfd_wqh, wait); spin_lock_irq(¤t->sighand->siglock); - if (next_signal(¤t->pending, &ctx->sigmask) || - next_signal(¤t->signal->shared_pending, - &ctx->sigmask)) + refine_sigmask(ctx, &sigmask); + if (next_signal(¤t->pending, &sigmask) || + next_signal(¤t->signal->shared_pending, &sigmask)) events |= EPOLLIN; spin_unlock_irq(¤t->sighand->siglock); @@ -155,11 +168,13 @@ static ssize_t signalfd_dequeue(struct signalfd_ctx *ctx, kernel_siginfo_t *info int nonblock) { enum pid_type type; - ssize_t ret; DECLARE_WAITQUEUE(wait, current); + sigset_t sigmask; + ssize_t ret; spin_lock_irq(¤t->sighand->siglock); - ret = dequeue_signal(&ctx->sigmask, info, &type); + refine_sigmask(ctx, &sigmask); + ret = dequeue_signal(&sigmask, info, &type); switch (ret) { case 0: if (!nonblock) @@ -174,7 +189,7 @@ static ssize_t signalfd_dequeue(struct signalfd_ctx *ctx, kernel_siginfo_t *info add_wait_queue(¤t->sighand->signalfd_wqh, &wait); for (;;) { set_current_state(TASK_INTERRUPTIBLE); - ret = dequeue_signal(&ctx->sigmask, info, &type); + ret = dequeue_signal(&sigmask, info, &type); if (ret != 0) break; if (signal_pending(current)) { @@ -184,6 +199,7 @@ static ssize_t signalfd_dequeue(struct signalfd_ctx *ctx, kernel_siginfo_t *info spin_unlock_irq(¤t->sighand->siglock); schedule(); spin_lock_irq(¤t->sighand->siglock); + refine_sigmask(ctx, &sigmask); } spin_unlock_irq(¤t->sighand->siglock); -- 2.53.0