From patchwork Wed Mar 5 10:08:15 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Christian Brauner X-Patchwork-Id: 14002273 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 CF2EF205E06 for ; Wed, 5 Mar 2025 10:08:37 +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=1741169317; cv=none; b=SqQY1I8MLSwuIVc3PBcliMGikdR2PWKGac2krk79KMFszv+HrvaofUK6VkopDyWfKtVLTiMBZpJoYa9ltqBUbeVpjTLA+5YGKcb8Ye9YMidihsIcSe1ONUTAik8k9gXn4BIVx46qVZ7/v5lq0YG0dn+Ga9d+GZqo7Cg5R1arHJU= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741169317; c=relaxed/simple; bh=JXrYrLNBggp1OwoK9I55On5p9kX9hSPyXO9PjAY+VL0=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=OX1q2z4yaAjemzRelbrkaAAhOSvinukxOJnEqD0/Me1VPRkGxhWQ+rjV6cT3FoCBn2ZwytJX2LVu+H+Aevu6IdiJjCwu838u0c1IsgZ8qW3o/Mq8AIzsrNcvytSxFGkP/AhwVyJdYMNhjWOi3MHztKlSSHpCCkVKa3sTEKWgOwA= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=GQdgrBr0; 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="GQdgrBr0" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C6AA3C4CEE9; Wed, 5 Mar 2025 10:08:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1741169317; bh=JXrYrLNBggp1OwoK9I55On5p9kX9hSPyXO9PjAY+VL0=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=GQdgrBr0eXadC8ytCTkN+FprhB53Sm2DcXRNF09bH0DzeP7rtxoJLUcf0ysIGFnXf nRLAKrwcbuFtaZvWO8AcpZp0n7tAgKykktly/pEEOEGQQhNjuJ9lNk3rbxZqAnJRU9 lzDAav8C5U/+SGfwtj/C5HIgnFVOhcaxbL4/DUkrFLHVfcrZv4F1f+V8OvnMGkR6jH zZ8+TpQ0j4rbp3QJ9sS4wzoAJy2JvlQf6HqiQDkLgjMus/XfrFpbg3Jtr3sWZTtnXe zPJsFIhbeAfhAaNi+aGjGyurYPmjl1P6hJATPwviwo0fazAJRFpomUkh8FzL/nZFvW wdHwDcAOlETFA== From: Christian Brauner Date: Wed, 05 Mar 2025 11:08:15 +0100 Subject: [PATCH v3 05/16] pidfs: record exit code and cgroupid at exit Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-Id: <20250305-work-pidfs-kill_on_last_close-v3-5-c8c3d8361705@kernel.org> References: <20250305-work-pidfs-kill_on_last_close-v3-0-c8c3d8361705@kernel.org> In-Reply-To: <20250305-work-pidfs-kill_on_last_close-v3-0-c8c3d8361705@kernel.org> To: Oleg Nesterov Cc: linux-fsdevel@vger.kernel.org, Jeff Layton , Lennart Poettering , Daan De Meyer , Mike Yuan , Christian Brauner X-Mailer: b4 0.15-dev-42535 X-Developer-Signature: v=1; a=openpgp-sha256; l=4649; i=brauner@kernel.org; h=from:subject:message-id; bh=JXrYrLNBggp1OwoK9I55On5p9kX9hSPyXO9PjAY+VL0=; b=owGbwMvMwCU28Zj0gdSKO4sYT6slMaSfUJohcL52T3LanAbHlP21AazhDCHaqfMDZhxTKXI61 HdbO3FpRykLgxgXg6yYIotDu0m43HKeis1GmRowc1iZQIYwcHEKwESWhDP8Zg8X/bMmN2JBYoNu 3le9UzsOfu14WH8x+s/DxDkLnNz31TL84dw2ad5kEaujXIWpS0995t37rLtX3yn2rKPKAwtBhat T2AA= X-Developer-Key: i=brauner@kernel.org; a=openpgp; fpr=4880B8C9BD0E5106FC070F4F7B3C391EFEA93624 Record the exit code and cgroupid in release_task() and stash in struct pidfs_exit_info so it can be retrieved even after the task has been reaped. Link: https://lore.kernel.org/r/20250304-work-pidfs-kill_on_last_close-v2-5-44fdacfaa7b7@kernel.org Reviewed-by: Jeff Layton Signed-off-by: Christian Brauner --- fs/internal.h | 1 + fs/libfs.c | 4 ++-- fs/pidfs.c | 41 +++++++++++++++++++++++++++++++++++++++++ include/linux/pidfs.h | 1 + kernel/exit.c | 2 ++ 5 files changed, 47 insertions(+), 2 deletions(-) diff --git a/fs/internal.h b/fs/internal.h index e7f02ae1e098..c1e6d8b294cb 100644 --- a/fs/internal.h +++ b/fs/internal.h @@ -325,6 +325,7 @@ struct stashed_operations { int path_from_stashed(struct dentry **stashed, struct vfsmount *mnt, void *data, struct path *path); void stashed_dentry_prune(struct dentry *dentry); +struct dentry *stashed_dentry_get(struct dentry **stashed); /** * path_mounted - check whether path is mounted * @path: path to check diff --git a/fs/libfs.c b/fs/libfs.c index 8444f5cc4064..cf5a267aafe4 100644 --- a/fs/libfs.c +++ b/fs/libfs.c @@ -2113,7 +2113,7 @@ struct timespec64 simple_inode_init_ts(struct inode *inode) } EXPORT_SYMBOL(simple_inode_init_ts); -static inline struct dentry *get_stashed_dentry(struct dentry **stashed) +struct dentry *stashed_dentry_get(struct dentry **stashed) { struct dentry *dentry; @@ -2215,7 +2215,7 @@ int path_from_stashed(struct dentry **stashed, struct vfsmount *mnt, void *data, const struct stashed_operations *sops = mnt->mnt_sb->s_fs_info; /* See if dentry can be reused. */ - path->dentry = get_stashed_dentry(stashed); + path->dentry = stashed_dentry_get(stashed); if (path->dentry) { sops->put_data(data); goto out_path; diff --git a/fs/pidfs.c b/fs/pidfs.c index 282511a36fd9..c4e6527013e7 100644 --- a/fs/pidfs.c +++ b/fs/pidfs.c @@ -458,6 +458,47 @@ struct pid *pidfd_pid(const struct file *file) return file_inode(file)->i_private; } +/* + * We're called from release_task(). We know there's at least one + * reference to struct pid being held that won't be released until the + * task has been reaped which cannot happen until we're out of + * release_task(). + * + * If this struct pid is referred to by a pidfd then + * stashed_dentry_get() will return the dentry and inode for that struct + * pid. Since we've taken a reference on it there's now an additional + * reference from the exit path on it. Which is fine. We're going to put + * it again in a second and we know that the pid is kept alive anyway. + * + * Worst case is that we've filled in the info and immediately free the + * dentry and inode afterwards since the pidfd has been closed. Since + * pidfs_exit() currently is placed after exit_task_work() we know that + * it cannot be us aka the exiting task holding a pidfd to ourselves. + */ +void pidfs_exit(struct task_struct *tsk) +{ + struct dentry *dentry; + + might_sleep(); + + dentry = stashed_dentry_get(&task_pid(tsk)->stashed); + if (dentry) { + struct inode *inode = d_inode(dentry); + struct pidfs_exit_info *exit_info = &pidfs_i(inode)->exit_info; +#ifdef CONFIG_CGROUPS + struct cgroup *cgrp; + + rcu_read_lock(); + cgrp = task_dfl_cgroup(tsk); + exit_info->cgroupid = cgroup_id(cgrp); + rcu_read_unlock(); +#endif + exit_info->exit_code = tsk->exit_code; + + dput(dentry); + } +} + static struct vfsmount *pidfs_mnt __ro_after_init; /* diff --git a/include/linux/pidfs.h b/include/linux/pidfs.h index 7c830d0dec9a..05e6f8f4a026 100644 --- a/include/linux/pidfs.h +++ b/include/linux/pidfs.h @@ -6,6 +6,7 @@ struct file *pidfs_alloc_file(struct pid *pid, unsigned int flags); void __init pidfs_init(void); void pidfs_add_pid(struct pid *pid); void pidfs_remove_pid(struct pid *pid); +void pidfs_exit(struct task_struct *tsk); extern const struct dentry_operations pidfs_dentry_operations; #endif /* _LINUX_PID_FS_H */ diff --git a/kernel/exit.c b/kernel/exit.c index 3485e5fc499e..9916305e34d3 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -69,6 +69,7 @@ #include #include #include +#include #include @@ -249,6 +250,7 @@ void release_task(struct task_struct *p) dec_rlimit_ucounts(task_ucounts(p), UCOUNT_RLIMIT_NPROC, 1); rcu_read_unlock(); + pidfs_exit(p); cgroup_release(p); write_lock_irq(&tasklist_lock);