From mboxrd@z Thu Jan 1 00:00:00 1970 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 DB6F3205501; Mon, 5 May 2025 11:14:27 +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=1746443668; cv=none; b=eWM7F+kMUOeXaJQmAaGJaV620egZAUJRIdYwQgq1w4kpwHXg31MWnykL6c0uXKwMn4SKSCG2nBHcd8X18E0fUEICs+inLHIfZP/mD+p9NVpa54B+udzvhalg7LenwRYElMKseG/s6HJx8F8VQ9wCWrDpjUXzOM1wtXT4t7a4GTg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1746443668; c=relaxed/simple; bh=FGPVAlSyUWiE0nw9P99qFYAvm4mIutgM8NSMMdkUFCM=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=tMuu7EShoBZbZcStyno2Aq0cxCcO5t42rZDOCFAoZwXD+MOJ9R5fr+C64GqSDupi30RmgXWWyfEZi9xOhSMmhc/OOcLLtOHtsFiyB7YFhcI5IC6UGhvJRkiVAQBfL+TvyC7IFK1QJPsgQWka/0npF+OpytYRe4fEbwblvYV1dJ0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=HFp94hgS; 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="HFp94hgS" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 16CAFC4CEE4; Mon, 5 May 2025 11:14:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1746443667; bh=FGPVAlSyUWiE0nw9P99qFYAvm4mIutgM8NSMMdkUFCM=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=HFp94hgSNHT4STF8tjcD3d09vh9bWUrSYBCcldMli0CHd8HAu9mRyJb0whMtwDwnz R6xmi+cjqx6bPjeWHWlikQFdFLLnel/8vFm1QRUwCzER0BEBsI7gMvZUifEpc1v+1h bVv95FM1TBB8IMf3pe3KGliWgrlo3f2cohQfLPfDTFB/EkWJwomTWxmSiCko38V7Jm VaJsrjgj9hVJHYcH4kiFs/Ka6LcoE5R29S/3qDVyyhsEb4UWItLxX8XW1ds7PHnxo0 YGBW8if8TAYllr0YhAOXlOSQb7v4q1/sKbtyr88DXCjN2ROrtXdElCVYPwCQZN2dg9 FRpuiLwFOxILg== From: Christian Brauner Date: Mon, 05 May 2025 13:13:45 +0200 Subject: [PATCH RFC v3 07/10] pidfs, coredump: add PIDFD_INFO_COREDUMP Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20250505-work-coredump-socket-v3-7-e1832f0e1eae@kernel.org> References: <20250505-work-coredump-socket-v3-0-e1832f0e1eae@kernel.org> In-Reply-To: <20250505-work-coredump-socket-v3-0-e1832f0e1eae@kernel.org> To: Eric Dumazet , Kuniyuki Iwashima , Oleg Nesterov , linux-fsdevel@vger.kernel.org, Jann Horn Cc: "David S. Miller" , Alexander Viro , Daan De Meyer , David Rheinsberg , Jakub Kicinski , Jan Kara , Lennart Poettering , Luca Boccassi , Mike Yuan , Paolo Abeni , Simon Horman , =?utf-8?q?Zbigniew_J=C4=99drzejewski-Szmek?= , linux-kernel@vger.kernel.org, netdev@vger.kernel.org, Christian Brauner , Alexander Mikhalitsyn X-Mailer: b4 0.15-dev-c25d1 X-Developer-Signature: v=1; a=openpgp-sha256; l=7705; i=brauner@kernel.org; h=from:subject:message-id; bh=FGPVAlSyUWiE0nw9P99qFYAvm4mIutgM8NSMMdkUFCM=; b=owGbwMvMwCU28Zj0gdSKO4sYT6slMWRIzM0Lv3v56PZHoVWTP5YJfPVam6z2uk9yvsSWZZqcF 1tbvknldJSyMIhxMciKKbI4tJuEyy3nqdhslKkBM4eVCWQIAxenAExEKoGRoTv+u7KYeFOOGoeJ 1amlCnNEmLeXrRSQPX7J5P+DaV9vfGL4p9Wbd7Y16l3ibD3n7mRFhX3ZbvWL5q94K7r97wFp9zt TeQE= X-Developer-Key: i=brauner@kernel.org; a=openpgp; fpr=4880B8C9BD0E5106FC070F4F7B3C391EFEA93624 Let userspace know that the task coredumped and whether it was dumped as root or as regular user. The latter is needed so that access permissions to the executable are correctly handled. I don't think this requires any additional privileges checks. The missing exposure of the dumpability attribute of a given task is an issue we should fix given that we already expose whether a task is coredumping or not. Signed-off-by: Christian Brauner --- fs/coredump.c | 35 +++++++++++++++++++++++++++++ fs/pidfs.c | 55 ++++++++++++++++++++++++++++++++++++++++++++++ include/linux/pidfs.h | 3 +++ include/uapi/linux/pidfd.h | 16 ++++++++++++++ 4 files changed, 109 insertions(+) diff --git a/fs/coredump.c b/fs/coredump.c index 37dc5aa3806f..a5f17aaeee32 100644 --- a/fs/coredump.c +++ b/fs/coredump.c @@ -46,7 +46,9 @@ #include #include #include +#include #include +#include #include #include @@ -588,6 +590,8 @@ static int umh_coredump_setup(struct subprocess_info *info, struct cred *new) if (IS_ERR(pidfs_file)) return PTR_ERR(pidfs_file); + pidfs_coredump(cp); + /* * Usermode helpers are childen of either * system_unbound_wq or of kthreadd. So we know that @@ -869,11 +873,42 @@ void do_coredump(const kernel_siginfo_t *siginfo) goto close_fail; } + /* + * Set the thread-group leader pid which is used for the + * peer credentials during connect() below. Then + * immediately register it in pidfs... + */ + cprm.pid = task_tgid(current); + retval = pidfs_register_pid(cprm.pid); + if (retval) { + sock_release(socket); + goto close_fail; + } + + /* + * ... and set the coredump information so userspace + * has it available after connect()... + */ + pidfs_coredump(&cprm); + + /* + * ... On connect() the peer credentials are recorded + * and @cprm.pid registered in pidfs... + */ retval = kernel_connect(socket, (struct sockaddr *)(&coredump_unix_socket), COREDUMP_UNIX_SOCKET_ADDR_SIZE, 0); + /* + * ... So we can safely put our pidfs reference now... + */ + pidfs_put_pid(cprm.pid); if (retval) goto close_fail; + /* ... and validate that @sk_peer_pid matches @cprm.pid. */ + if (WARN_ON_ONCE(unix_peer(socket->sk)->sk_peer_pid != cprm.pid)) { + retval = -ESRCH; + goto close_fail; + } cprm.limit = RLIM_INFINITY; #endif diff --git a/fs/pidfs.c b/fs/pidfs.c index 3b39e471840b..8c4d83fb115b 100644 --- a/fs/pidfs.c +++ b/fs/pidfs.c @@ -20,6 +20,7 @@ #include #include #include +#include #include "internal.h" #include "mount.h" @@ -33,6 +34,7 @@ static struct kmem_cache *pidfs_cachep __ro_after_init; struct pidfs_exit_info { __u64 cgroupid; __s32 exit_code; + __u32 coredump_mask; }; struct pidfs_inode { @@ -240,6 +242,22 @@ static inline bool pid_in_current_pidns(const struct pid *pid) return false; } +static __u32 pidfs_coredump_mask(unsigned long mm_flags) +{ + switch (__get_dumpable(mm_flags)) { + case SUID_DUMP_USER: + return PIDFD_COREDUMP_USER; + case SUID_DUMP_ROOT: + return PIDFD_COREDUMP_ROOT; + case SUID_DUMP_DISABLE: + return PIDFD_COREDUMP_SKIP; + default: + WARN_ON_ONCE(true); + } + + return 0; +} + static long pidfd_info(struct file *file, unsigned int cmd, unsigned long arg) { struct pidfd_info __user *uinfo = (struct pidfd_info __user *)arg; @@ -280,6 +298,11 @@ static long pidfd_info(struct file *file, unsigned int cmd, unsigned long arg) } } + if (mask & PIDFD_INFO_COREDUMP) { + kinfo.mask |= PIDFD_INFO_COREDUMP; + kinfo.coredump_mask = READ_ONCE(pidfs_i(inode)->__pei.coredump_mask); + } + task = get_pid_task(pid, PIDTYPE_PID); if (!task) { /* @@ -296,6 +319,13 @@ static long pidfd_info(struct file *file, unsigned int cmd, unsigned long arg) if (!c) return -ESRCH; + if (!(kinfo.mask & PIDFD_INFO_COREDUMP)) { + task_lock(task); + if (task->mm) + kinfo.coredump_mask = pidfs_coredump_mask(task->mm->flags); + task_unlock(task); + } + /* Unconditionally return identifiers and credentials, the rest only on request */ user_ns = current_user_ns(); @@ -559,6 +589,31 @@ void pidfs_exit(struct task_struct *tsk) } } +void pidfs_coredump(const struct coredump_params *cprm) +{ + struct pid *pid = cprm->pid; + struct pidfs_exit_info *exit_info; + struct dentry *dentry; + struct inode *inode; + __u32 coredump_mask = 0; + + dentry = stashed_dentry_get(&pid->stashed); + if (WARN_ON_ONCE(!dentry)) + return; + + inode = d_inode(dentry); + exit_info = &pidfs_i(inode)->__pei; + /* Note how we were coredumped. */ + coredump_mask = pidfs_coredump_mask(cprm->mm_flags); + /* Note that we actually did coredump. */ + coredump_mask |= 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(&exit_info->coredump_mask, coredump_mask); + /* Fwiw, this cannot be the last reference. */ + dput(dentry); +} + static struct vfsmount *pidfs_mnt __ro_after_init; /* diff --git a/include/linux/pidfs.h b/include/linux/pidfs.h index 2676890c4d0d..f7729b9371bc 100644 --- a/include/linux/pidfs.h +++ b/include/linux/pidfs.h @@ -2,11 +2,14 @@ #ifndef _LINUX_PID_FS_H #define _LINUX_PID_FS_H +struct coredump_params; + 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); +void pidfs_coredump(const struct coredump_params *cprm); extern const struct dentry_operations pidfs_dentry_operations; int pidfs_register_pid(struct pid *pid); void pidfs_get_pid(struct pid *pid); diff --git a/include/uapi/linux/pidfd.h b/include/uapi/linux/pidfd.h index 8c1511edd0e9..84ac709f560c 100644 --- a/include/uapi/linux/pidfd.h +++ b/include/uapi/linux/pidfd.h @@ -25,9 +25,23 @@ #define PIDFD_INFO_CREDS (1UL << 1) /* Always returned, even if not requested */ #define PIDFD_INFO_CGROUPID (1UL << 2) /* Always returned if available, even if not requested */ #define PIDFD_INFO_EXIT (1UL << 3) /* Only returned if requested. */ +#define PIDFD_INFO_COREDUMP (1UL << 4) /* Only returned if requested. */ #define PIDFD_INFO_SIZE_VER0 64 /* sizeof first published struct */ +/* + * Values for @coredump_mask in pidfd_info. + * Only valid if PIDFD_INFO_SUID_COREDUMP is set in @mask. + * + * Note, the @PIDFD_COREDUMP_ROOT flag indicates that the generated + * coredump should be treated as sensitive and access should only be + * granted to privileged users. + */ +#define PIDFD_COREDUMPED (1U << 0) /* Did crash and... */ +#define PIDFD_COREDUMP_SKIP (1U << 1) /* coredumping generation was skipped. */ +#define PIDFD_COREDUMP_USER (1U << 2) /* coredump was done as the user. */ +#define PIDFD_COREDUMP_ROOT (1U << 3) /* coredump was done as root. */ + /* * The concept of process and threads in userland and the kernel is a confusing * one - within the kernel every thread is a 'task' with its own individual PID, @@ -92,6 +106,8 @@ struct pidfd_info { __u32 fsuid; __u32 fsgid; __s32 exit_code; + __u32 coredump_mask; + __u32 __spare1; }; #define PIDFS_IOCTL_MAGIC 0xFF -- 2.47.2