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=1793222617; b=Ks81hsS57m0iv/eJhvIKSlzJVWaq7v/uOX4SWaHTzjvQYJyZvJHUgGEB7PUvA5Uqbuvn u7V1t2r5JsQ83o2Krs/hAfy+nRZwSUxK7a7GVPTySf9478UfUXG8BrSafzIRE3MGiZTiG 1rMDtBXclz4K0MBe+0vhz2Ru/wYwQ/ErowtQIFI/ERPfQXLOslrhuvK89LDdid4xDxo7K 0t28xJu5rPLLw+fj8VEShknQJMOKV3BEZSVijaKRhaaxlYQ7Uo2OeQYgAsVs/QN5my0Z0 hwrVBMFO6uOq1sfGc68xb3ryxj8oY13ruBEbutVmajtYRex7/dbkARZ5By0/1/vYINA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793222617; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Transfer-Encoding; bh=FQcCz7kORXSYgc7G1jAsRlvMGdpA/Kf4rXJDDVpXV2c=; b=4sH05vhUzcTGLngIgx5pbF4S6uRliaddDdANVV1olbZPfHe4B+8srk/RgWhn6x9nj2Fa ElFmMGXnjUgyttGwvdQnckmxAPFsTmOMSc3z6N8wfdtGrSx7/rndjL77g4nCyPf2NMDaL gPywPFEesN0pnSv4LO+dBg6+QtsnygmlaQkdFLHYPnFljOPyYcNGJ3yGEllsgmkHZFHLN IJqzE6p8xma5r+WKZDCvCsG8N+gJdeS+UkZs92onqkHPh5j89kWUm0C1bfLgnBV4zrInq ovfXurK23aADXTahg7GUR11B5mYZlPG3OqJK4z8epahKkD2xnSvpyEVUtVnGAPC8ewQ== 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=GwByTERy; 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 05348606A330 for ; Wed, 28 Oct 2026 21:23:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=GwByTERy Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2FABA1F01829; Wed, 28 Oct 2026 21:23:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793222616; bh=FQcCz7kORXSYgc7G1jAsRlvMGdpA/Kf4rXJDDVpXV2c=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=GwByTERyefoOLTDBHbXyoGizKkhiUEVPBunWdakCLEjsgFUYlJyL6BdotSqf6Dpq/ z6PH8cHl90kx6Rj9bHxWsW5Bi5dcRrWlIwb0hNdmL91OEdOfP5VXSttsBAFBTLNPS1 DgxEibJsM8UaDNCmLn5UrSm5kQ9+GFxJ3tOWNftoWhKhGUCl82/gfSbQMJGnWYEGf3 l+CDEnDD7OrivjNOgNJOBYSkxavE/3QtTk5Zh6JAZZuRZEQcQ2rw5uXvZEp6BzePPk d982hxILnK1TY3DMm5/X1jkZKKaHL9YBsLcUKwmA9F4JzCfjPX0CIbulKWqGOeKYjZ SajHcmUXmDG+w== From: Sasha Levin To: stable@vger.kernel.org Cc: Christian Brauner , Oleg Nesterov , Sasha Levin Subject: [PATCH 5.15.y] signal: allow taks to temporarily block TIF_NOTIFY_SIGNAL Date: Wed, 28 Oct 2026 17:23:34 -0400 Message-ID: <20261028212317.2257095-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <2026102837-poem-blog-9727@gregkh> References: <2026102837-poem-blog-9727@gregkh> 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 From: Christian Brauner [ Upstream commit 22b7f491be8f93ff72de0a3fe02b8ee9e64d3f21 ] TIF_NOTIFY_SIGNAL is used to kick a task in uninterruptible sleep to return to userspace and run task work and then go back to sleep. This mechanism works well but breaks e.g., coredumps. dump_interrupted() only allows fatal signals to interrupt a coredump and the whole regular write path going to actual filesystems is impervious to TIF_NOTIFY_SIGNAL as well. Add PF_NO_NOTIFY_SIGNAL and helpers to raise and restore it. This is the same approach as memalloc_nofs_save(). signal_pending() will not report a fake pending signal via TIF_NOTIFY_SIGNAL if inside a PF_NO_NOTIFY_SIGNAL section. No functional changes. Link: https://patch.msgid.link/20260824-work-tif_notify_signal-v2-1-6609e42b3157@kernel.org Reviewed-by: Oleg Nesterov Cc: stable@vger.kernel.org Signed-off-by: Christian Brauner (Amutable) [ sashal: Assigned PF_NO_NOTIFY_SIGNAL to 0x01000000 instead of 0x00800000 to avoid colliding with PF_SWAPWRITE. ] Signed-off-by: Sasha Levin --- include/linux/sched.h | 1 + include/linux/sched/signal.h | 27 +++++++++++++++++++++++++-- 2 files changed, 26 insertions(+), 2 deletions(-) diff --git a/include/linux/sched.h b/include/linux/sched.h index 561fb81675fa5..523d727d27a70 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1703,6 +1703,7 @@ extern struct pid *cad_pid; #define PF_KTHREAD 0x00200000 /* I am a kernel thread */ #define PF_RANDOMIZE 0x00400000 /* Randomize virtual address space */ #define PF_SWAPWRITE 0x00800000 /* Allowed to write to swap */ +#define PF_NO_NOTIFY_SIGNAL 0x01000000 /* see no_notify_signal_save() */ #define PF_NO_SETAFFINITY 0x04000000 /* Userland is not allowed to meddle with cpus_mask */ #define PF_MCE_EARLY 0x08000000 /* Early kill for mce process policy */ #define PF_MEMALLOC_PIN 0x10000000 /* Allocation context constrained to zones which allow long term pinning. */ diff --git a/include/linux/sched/signal.h b/include/linux/sched/signal.h index 324a3fd0f3c3e..19298445a6ce6 100644 --- a/include/linux/sched/signal.h +++ b/include/linux/sched/signal.h @@ -2,6 +2,7 @@ #ifndef _LINUX_SCHED_SIGNAL_H #define _LINUX_SCHED_SIGNAL_H +#include #include #include #include @@ -365,14 +366,36 @@ static inline int task_sigpending(struct task_struct *p) return unlikely(test_tsk_thread_flag(p,TIF_SIGPENDING)); } +/* Prevent TIF_NOTIFY_SIGNAL from interrupting this task. */ +static inline unsigned int no_notify_signal_save(void) +{ + unsigned int flags = current->flags; + + current->flags |= PF_NO_NOTIFY_SIGNAL; + return flags; +} + +/* Restore the previous PF_NO_NOTIFY_SIGNAL state. */ +static inline void no_notify_signal_restore(unsigned int flags) +{ + current_restore_flags(flags, PF_NO_NOTIFY_SIGNAL); +} + +DEFINE_LOCK_GUARD_0(no_notify_signal, + _T->flags = no_notify_signal_save(), + no_notify_signal_restore(_T->flags), + unsigned int flags) + static inline int signal_pending(struct task_struct *p) { /* * TIF_NOTIFY_SIGNAL isn't really a signal, but it requires the same * behavior in terms of ensuring that we break out of wait loops - * so that notify signal callbacks can be processed. + * so that notify signal callbacks can be processed. Not for a task + * that asked not to be interrupted by it, see no_notify_signal_save(). */ - if (unlikely(test_tsk_thread_flag(p, TIF_NOTIFY_SIGNAL))) + if (unlikely(test_tsk_thread_flag(p, TIF_NOTIFY_SIGNAL)) && + likely(!(READ_ONCE(p->flags) & PF_NO_NOTIFY_SIGNAL))) return 1; return task_sigpending(p); } -- 2.53.0