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=1794047383; b=C0AaNyZ51bWoMl1Fr/Idosmh7/Tuv7LE1p+nYHzUelkfb2LzmXh6oL9pJWzEtPzSeJQw orQvI/hJvctrjc2LFzVnmK01aXaMXvgzVV9R4hCAd9SwDr31BudTm5LNo1nup+t69kOvD L4Y5yEFbFrV9qc2kQQuyRCmj6qiaQSt//Rm3T7th5ZqrsUPDBWqu/zsaf6axYNs1SXO6W PFpSZO7lVEgXUcc4SiPbjc5QLWWsnrOWEJfScFfsY4bo0BqW3o9WSf/94c8/kPvXg9AQN dJoOwEs4U7xUPgePp0pgQWZAkByPrc5ZK1hHalueT4Q3U2SGYZBoH94MZPnvVmXjkOA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794047383; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: MIME-Version:Content-Type:Content-Transfer-Encoding; bh=5nfhaou7L472Eqm7dCslydmXwfgpU8T8u9IUOkKAM4w=; b=zRjqIfSnlye3rWs0ifvZVAxjJn+42p3Tx3xTN4FGxxfKyuh1mrJsOB9csWj8slq+vt62 Pofg328/A7W1QDYvL3FddNTDwjWV1UGX8D9C8ueRmstB+gqo53Pae+3lIxMk2WQsEJImv lcSNouPOMafZlW5ep0HIjARvyhFIdGryN28yJZwMe1KspXg1c3juqH0wmSCeXm9Smb7BJ GlfUeoG+0taUfLRnjbX7N1V5qz4UtTL7D8+EwlM+axWw+0h1ygp446j0qKu21QQfm1E3W P8uDGpNts3IMaLm7XrFsXqfnetRExx23sIakOCM46U39ujv+JY2+T4WvJ46PiwLg5og== 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=m4jTlfGS; 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 27611606A326 for ; Sat, 7 Nov 2026 10:29:43 +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=m4jTlfGS Received: by smtp.kernel.org (Postfix) with ESMTPSA id 819221F0089F; Sat, 7 Nov 2026 10:29:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794047383; bh=5nfhaou7L472Eqm7dCslydmXwfgpU8T8u9IUOkKAM4w=; h=From:To:Cc:Subject:Date; b=m4jTlfGSwWE4WoYui5gnVdZmRVLk5/tq9DaJAiuymrbzz+uufUh4AzEN/VzeQ5lMP dNuS6TG8tUyjkVaWas3KAHXcg6IlAJzWsoCFft180TQhY2gxNs90WZRNtm5CnJExKX bkOQP+MzLvVcNGy40KuRAIO3fTvo/zI+NR62LyYMD/47Rqi2eN4t/5HDvz0fjcOyeZ 4SPrZAKyRxQERPx8u8boA5pfolpnVpexN3Wfqe9pHb81nqXGrtb1HJIYwAIoBqL35/ FIMANwrgcbod+t3iaEMB+PMTnCKsvdDbyQvuvv3P86JO+8QoKbGdi4+WhDLk7VzHEQ LqnAUu84u8u3w== 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 6.6-stable tree Date: Sat, 7 Nov 2026 05:29:41 -0500 Message-ID: <20261107052941-failed-6.6-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 6.6-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-6.6.y git checkout FETCH_HEAD git cherry-pick -x d72e0fb3b00c6a1146bcfd7186ad9f6f609ba236 # git commit -s git send-email --to '' --in-reply-to '20261107052941-failed-6.6-d72e0fb3b00c@kernel.org' --subject-prefix 'PATCH 6.6.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