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=1794062901; b=ktC1QgLvFsnHTdiYzgKRfnXew0GsBMefM4T4WZhVPRUdg53FxbvuRwNOyTdVEgDBv8la 3mQZg65azfBcYwrz1VLWtNWzk6yJ87ldfnsvw+MQQSjrG/XBXV7gkNUCFHk84bfwbZ0/c O2B0mGrmn68IWycjZJw0GvPRJ7MzTsq/wRVCyR8K7BVMoYRThRyWc6oj5K98Q+Rvgwxjs 0z55DlQxRHGbin73Xe7ldOImdc/NzqSSBy56aZ2SL1/nQiJgNtejjyHtqlrTeQ6hyD0L5 mupu/lDvFPdRbyUW5Hitzl+mqadmPsMJq1DgzXVoqF5oP81T5YhUPNxjUDflnquhd0Q== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794062901; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:User-Agent:X-stable:X-Patchwork-Hint: MIME-Version:Content-Transfer-Encoding; bh=MhDvUluQQFh7hFyZmNED3CeDhl4i4yf0NB/jUB/8ABg=; b=ca0taiEeW+YHJOU6l6lAFDiQKLn6TY6Cien6T3KOuSLZ9BaXKRPHq1i/RbL3LdGIpZqH 9GMy3wTz9qZR6dtJDlQPCQobbLY7iaUVAdGmYfoGFXBK+UsBYGomhN2l2bKpzSw+FaVx1 ZCVxhtoIoFVKIkD4B6ros7Iz5XuCls199c2976Ke29frUrDccr+1QeqJOFT62Z0qF4Yv2 iEO3MkEBYecF/44cs9X397bhjuT1WAj5izWyofDjoMyoi9noLTZwqAtOPKkHJXAwTsS70 G3EbnlPEeQ7desD1Ol7qNl+1lGlTkYHbdn4YFmzcePMtzKJhyGcAxKTlabarP4Yb7nA== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b="lR/a+H3O"; 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 4EB90606A32F; Sat, 7 Nov 2026 14:48:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=lR/a+H3O Received: by smtp.kernel.org (Postfix) with ESMTPSA id 01A791F0089F; Sat, 7 Nov 2026 14:48:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1794062901; bh=MhDvUluQQFh7hFyZmNED3CeDhl4i4yf0NB/jUB/8ABg=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=lR/a+H3OU9CVkKWIgxn1WHuZoHUsKM2TAxMVvSoTlI/TMIhxyuuNL1UgNOPdIPg4r v8ey9jHSDhCF0seMb7S4UzhvNiospP5V9SMalcJ9POEU9p+HcLlZ8TdM+K6SqMSNxn ypprqfsfBqQ0i9ilJUYJPYGODhT7cRTWju14dWFo= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, stable@kernel.org, syzbot+0a4c46806941297fecb9@syzkaller.appspotmail.com, Kusaram Devineni , Oleg Nesterov , Kees Cook , Sasha Levin Subject: [PATCH 6.18 176/869] signalfd: dont dequeue the forced fatal signals Date: Sat, 7 Nov 2026 08:47:38 -0500 Message-ID: <20261107134858.141640290@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261107134852.069646174@linuxfoundation.org> References: <20261107134852.069646174@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore 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-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Oleg Nesterov [ Upstream commit d72e0fb3b00c6a1146bcfd7186ad9f6f609ba236 ] 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 Signed-off-by: Sasha Levin --- fs/signalfd.c | 28 ++++++++++++++++++++++------ 1 file changed, 22 insertions(+), 6 deletions(-) diff --git a/fs/signalfd.c b/fs/signalfd.c index d469782f97f4d..0aa1657bbedf6 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