From nobody Mon Feb 9 10:27:11 2026 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 816DC2DAFA1; Tue, 28 Oct 2025 08:46:37 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761641197; cv=none; b=S8bHqFeWmAa43qNa8dx/gjIUUcJeSaW4+eMUpWDy0tgs2EnmAqwmq+FWjNzPgXqEC0IzxkR8HTy280qsp0Jp+ABP2fE2D8cZlNFNIEDlNxOb4hulNXHqJaG3rKq7i16Oh2oSv9lUqVpYwOa+TNJOLc5Bdmo6IcpZNiVkSTjx/mI= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761641197; c=relaxed/simple; bh=CqBLua7mC1jnX91nIzWy68mJTdDx9M0GCh7rqkQtFj4=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=NBcghZqQgixBjTUF/WIo79Kafwo8fRyuzdZ36zYgXES2RvqSNdOyuuzYJuz2WW3ZqCMCR7w2fFEHBiIyS4H5wpxLQR5hl4zWgfx99v3g2d93rfst5eFDsaBL3VZtIBUtmlBAZUXZVgVQFeG7yc1sGlJZMQT5/Icn3ukNMaqiqc0= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=TaG8r5Cw; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="TaG8r5Cw" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7DF5CC4CEE7; Tue, 28 Oct 2025 08:46:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1761641197; bh=CqBLua7mC1jnX91nIzWy68mJTdDx9M0GCh7rqkQtFj4=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=TaG8r5CwImD2ut7WGFRwKxHNou55SZHOpBjSUdIZ1qoxM7vj+Zw6ZtByujlkjrgJM K4EqIFWMfnEEhCk119s02QqkQtp3es0bRtBqn1rX2fyN/5/JrrR911UleSlspbGxR5 MsQgQYWSew3LfjajJ0M0qsnYF3pa+d3vbz/Ksl4poqk9s3CgGxSDVYwjVYfDC0yzoR rE4cMMTB6tuZSeb/beL/RYUskJ7/hN+0dYSM8SxBTfgWznILE3sOpbq3VoYNylGlZ/ 87thZk5+joxFEMjWNgXiyTjNQh+y0FfD23/SN3FnqYvsW42IitZGiSKM/RqhYOYGIl 0qZiRZa1mxUXA== From: Christian Brauner Date: Tue, 28 Oct 2025 09:45:53 +0100 Subject: [PATCH 08/22] pidfs: expose coredump signal Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20251028-work-coredump-signal-v1-8-ca449b7b7aa0@kernel.org> References: <20251028-work-coredump-signal-v1-0-ca449b7b7aa0@kernel.org> In-Reply-To: <20251028-work-coredump-signal-v1-0-ca449b7b7aa0@kernel.org> To: linux-fsdevel@vger.kernel.org Cc: Oleg Nesterov , Amir Goldstein , Aleksa Sarai , Yu Watanabe , Josef Bacik , Jeff Layton , Jann Horn , Luca Boccassi , Alexander Mikhalitsyn , linux-kernel@vger.kernel.org, Alexander Viro , Jan Kara , Lennart Poettering , Mike Yuan , =?utf-8?q?Zbigniew_J=C4=99drzejewski-Szmek?= , Christian Brauner X-Mailer: b4 0.15-dev-96507 X-Developer-Signature: v=1; a=openpgp-sha256; l=4285; i=brauner@kernel.org; h=from:subject:message-id; bh=CqBLua7mC1jnX91nIzWy68mJTdDx9M0GCh7rqkQtFj4=; b=kA0DAAoWkcYbwGV43KIByyZiAGkAgsGic1ncXqnT9faYYabTX80a5gw0OGbFlvIbAF3/0UPAc oh1BAAWCgAdFiEEQIc0Vx6nDHizMmkokcYbwGV43KIFAmkAgsEACgkQkcYbwGV43KLUmAD+LqY5 B0JB0lVYhW0lcAWiEY7RemBxIpe+xvr7Chw4uU8A/199f95a6vHxn2d5lcYXyfiBXSzsSxRc/Kb 82zAHt2AM X-Developer-Key: i=brauner@kernel.org; a=openpgp; fpr=4880B8C9BD0E5106FC070F4F7B3C391EFEA93624 Userspace needs access to the signal that caused the coredump before the coredumping process has been reaped. Expose it as part of the coredump information in struct pidfd_info. After the process has been reaped that info is also available as part of PIDFD_INFO_EXIT's exit_code field. Signed-off-by: Christian Brauner Reviewed-by: Alexander Mikhalitsyn --- fs/pidfs.c | 30 +++++++++++++++++++----------- include/uapi/linux/pidfd.h | 7 +++++-- 2 files changed, 24 insertions(+), 13 deletions(-) diff --git a/fs/pidfs.c b/fs/pidfs.c index a3b80be3b98b..354ceb2126e7 100644 --- a/fs/pidfs.c +++ b/fs/pidfs.c @@ -41,6 +41,7 @@ void pidfs_get_root(struct path *path) =20 enum pidfs_attr_mask_bits { PIDFS_ATTR_BIT_EXIT =3D 0, + PIDFS_ATTR_BIT_COREDUMP =3D 1, }; =20 struct pidfs_attr { @@ -51,6 +52,7 @@ struct pidfs_attr { __s32 exit_code; }; __u32 coredump_mask; + __u32 coredump_signal; }; =20 static struct rb_root pidfs_ino_tree =3D RB_ROOT; @@ -297,7 +299,8 @@ static __u32 pidfs_coredump_mask(unsigned long mm_flags) PIDFD_INFO_CGROUPID | \ PIDFD_INFO_EXIT | \ PIDFD_INFO_COREDUMP | \ - PIDFD_INFO_SUPPORTED_MASK) + PIDFD_INFO_SUPPORTED_MASK | \ + PIDFD_INFO_COREDUMP_SIGNAL) =20 static long pidfd_info(struct file *file, unsigned int cmd, unsigned long = arg) { @@ -342,9 +345,12 @@ static long pidfd_info(struct file *file, unsigned int= cmd, unsigned long arg) } =20 if (mask & PIDFD_INFO_COREDUMP) { - kinfo.coredump_mask =3D READ_ONCE(attr->coredump_mask); - if (kinfo.coredump_mask) - kinfo.mask |=3D PIDFD_INFO_COREDUMP; + if (test_bit(PIDFS_ATTR_BIT_COREDUMP, &attr->attr_mask)) { + smp_rmb(); + kinfo.mask |=3D PIDFD_INFO_COREDUMP | PIDFD_INFO_COREDUMP_SIGNAL; + kinfo.coredump_mask =3D attr->coredump_mask; + kinfo.coredump_signal =3D attr->coredump_signal; + } } =20 task =3D get_pid_task(pid, PIDTYPE_PID); @@ -370,6 +376,7 @@ static long pidfd_info(struct file *file, unsigned int = cmd, unsigned long arg) =20 kinfo.coredump_mask =3D pidfs_coredump_mask(flags); kinfo.mask |=3D PIDFD_INFO_COREDUMP; + /* No coredump actually took place, so no coredump signal. */ } } =20 @@ -666,20 +673,21 @@ void pidfs_coredump(const struct coredump_params *cpr= m) { struct pid *pid =3D cprm->pid; struct pidfs_attr *attr; - __u32 coredump_mask =3D 0; =20 attr =3D READ_ONCE(pid->attr); =20 VFS_WARN_ON_ONCE(!attr); VFS_WARN_ON_ONCE(attr =3D=3D PIDFS_PID_DEAD); =20 - /* Note how we were coredumped. */ - coredump_mask =3D pidfs_coredump_mask(cprm->mm_flags); - /* Note that we actually did coredump. */ - coredump_mask |=3D PIDFD_COREDUMPED; + /* Note how we were coredumped and that we coredumped. */ + attr->coredump_mask =3D pidfs_coredump_mask(cprm->mm_flags) | + PIDFD_COREDUMPED; /* If coredumping is set to skip we should never end up here. */ - VFS_WARN_ON_ONCE(coredump_mask & PIDFD_COREDUMP_SKIP); - smp_store_release(&attr->coredump_mask, coredump_mask); + VFS_WARN_ON_ONCE(attr->coredump_mask & PIDFD_COREDUMP_SKIP); + /* Expose the signal number that caused the coredump. */ + attr->coredump_signal =3D cprm->siginfo->si_signo; + smp_wmb(); + set_bit(PIDFS_ATTR_BIT_COREDUMP, &attr->attr_mask); } #endif =20 diff --git a/include/uapi/linux/pidfd.h b/include/uapi/linux/pidfd.h index e05caa0e00fe..ea9a6811fc76 100644 --- a/include/uapi/linux/pidfd.h +++ b/include/uapi/linux/pidfd.h @@ -27,6 +27,7 @@ #define PIDFD_INFO_EXIT (1UL << 3) /* Only returned if requested. */ #define PIDFD_INFO_COREDUMP (1UL << 4) /* Only returned if requested. */ #define PIDFD_INFO_SUPPORTED_MASK (1UL << 5) /* Want/got supported mask fl= ags */ +#define PIDFD_INFO_COREDUMP_SIGNAL (1UL << 6) /* Always returned if PIDFD_= INFO_COREDUMP is requested. */ =20 #define PIDFD_INFO_SIZE_VER0 64 /* sizeof first published struct */ #define PIDFD_INFO_SIZE_VER1 72 /* sizeof second published struct */ @@ -94,8 +95,10 @@ struct pidfd_info { __u32 fsuid; __u32 fsgid; __s32 exit_code; - __u32 coredump_mask; - __u32 __spare1; + struct /* coredump info */ { + __u32 coredump_mask; + __u32 coredump_signal; + }; __u64 supported_mask; /* Mask flags that this kernel supports */ }; =20 --=20 2.47.3