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 711383E0757; Tue, 12 May 2026 17:46:38 +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=1778607998; cv=none; b=gk5E5vs4tnqxQJSISRxDCrX9LPokIcuryiQjOrMxPMohzVhbs8KdcM9pFz1xKsz3WJE4vfcLZ05VSwdhV7ltyAvP6eZYBfevxAyZzqrP3I63Z+6lhxBdrQMiihHxF0/65eLwyliu0WSpz+domjK7vH4GAZHLrJcZ9AUoRyTaof8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778607998; c=relaxed/simple; bh=emEsOPB1o9dJIwPyXMNW7t6RAvm0stF20pycHgxOc60=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Nj2dZvs0mIhNCkGco0bIWY3931TGKIpMMrqxYjZcK4LEK3KZfCE/DuDlyjnCtUcfLrLBIYprnTJf65OfLtBG4gJrFydEWygUMft0WV5NhLcwGy9LyQtfzRwS1AFZUi/BS71gf9Usju2geDqdFgABnQnSteUYTHwQVXuJWipOCD0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=ypTcJg6q; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="ypTcJg6q" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 08C4FC2BCF5; Tue, 12 May 2026 17:46:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1778607998; bh=emEsOPB1o9dJIwPyXMNW7t6RAvm0stF20pycHgxOc60=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ypTcJg6qq9aPiGCfUpRkoqXHUU/eD5icDjNJJyHH8QCF63CkJMhlDXd6I8gbKhfF9 kmS84XOK8LIXCua0eF2HAQEPzTI+6bqzz69R/D01tdtyyifqu4dfSMGSkeINPgIN2K O5lwS6o9WgeRQoDC3taUs0gX3DFQlf5DiHLBwj0c= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, David Carlier , Steven Rostedt Subject: [PATCH 6.12 118/206] eventfs: Hold eventfs_mutex and SRCU when remount walks events Date: Tue, 12 May 2026 19:39:30 +0200 Message-ID: <20260512173935.355159404@linuxfoundation.org> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260512173932.810559588@linuxfoundation.org> References: <20260512173932.810559588@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: David Carlier commit 07004a8c4b572171934390148ee48c4175c77eed upstream. Commit 340f0c7067a9 ("eventfs: Update all the eventfs_inodes from the events descriptor") had eventfs_set_attrs() recurse through ei->children on remount. The walk only holds the rcu_read_lock() taken by tracefs_apply_options() over tracefs_inodes, which is wrong: - list_for_each_entry over ei->children races with the list_del_rcu() in eventfs_remove_rec() -- LIST_POISON1 deref, same shape as d2603279c7d6. - eventfs_inodes are freed via call_srcu(&eventfs_srcu, ...). rcu_read_lock() does not extend an SRCU grace period, so ti->private can be reclaimed under the walk. - The writes to ei->attr race with eventfs_set_attr(), which holds eventfs_mutex. Reproducer: while :; do mount -o remount,uid=$((RANDOM%1000)) /sys/kernel/tracing; done & while :; do echo "p:kp submit_bio" > /sys/kernel/tracing/kprobe_events echo > /sys/kernel/tracing/kprobe_events done Wrap the events portion of tracefs_apply_options() in eventfs_remount_lock()/_unlock() that take eventfs_mutex and srcu_read_lock(&eventfs_srcu). eventfs_set_attrs() doesn't sleep so the nested rcu_read_lock() is fine; lockdep_assert_held() pins the contract. Comment in tracefs_drop_inode() said "RCU cycle" -- it is SRCU. Fixes: 340f0c7067a9 ("eventfs: Update all the eventfs_inodes from the events descriptor") Cc: stable@vger.kernel.org Link: https://patch.msgid.link/20260418191737.10289-1-devnexen@gmail.com Signed-off-by: David Carlier Signed-off-by: Steven Rostedt Signed-off-by: Greg Kroah-Hartman --- fs/tracefs/event_inode.c | 14 ++++++++++++++ fs/tracefs/inode.c | 5 ++++- fs/tracefs/internal.h | 3 +++ 3 files changed, 21 insertions(+), 1 deletion(-) --- a/fs/tracefs/event_inode.c +++ b/fs/tracefs/event_inode.c @@ -250,6 +250,8 @@ static void eventfs_set_attrs(struct eve { struct eventfs_inode *ei_child; + lockdep_assert_held(&eventfs_mutex); + /* Update events// */ if (WARN_ON_ONCE(level > 3)) return; @@ -912,3 +914,15 @@ void eventfs_remove_events_dir(struct ev d_invalidate(dentry); dput(dentry); } + +int eventfs_remount_lock(void) +{ + mutex_lock(&eventfs_mutex); + return srcu_read_lock(&eventfs_srcu); +} + +void eventfs_remount_unlock(int srcu_idx) +{ + srcu_read_unlock(&eventfs_srcu, srcu_idx); + mutex_unlock(&eventfs_mutex); +} --- a/fs/tracefs/inode.c +++ b/fs/tracefs/inode.c @@ -336,6 +336,7 @@ static int tracefs_apply_options(struct struct inode *inode = d_inode(sb->s_root); struct tracefs_inode *ti; bool update_uid, update_gid; + int srcu_idx; umode_t tmp_mode; /* @@ -360,6 +361,7 @@ static int tracefs_apply_options(struct update_uid = fsi->opts & BIT(Opt_uid); update_gid = fsi->opts & BIT(Opt_gid); + srcu_idx = eventfs_remount_lock(); rcu_read_lock(); list_for_each_entry_rcu(ti, &tracefs_inodes, list) { if (update_uid) { @@ -381,6 +383,7 @@ static int tracefs_apply_options(struct eventfs_remount(ti, update_uid, update_gid); } rcu_read_unlock(); + eventfs_remount_unlock(srcu_idx); } return 0; @@ -426,7 +429,7 @@ static int tracefs_drop_inode(struct ino * This inode is being freed and cannot be used for * eventfs. Clear the flag so that it doesn't call into * eventfs during the remount flag updates. The eventfs_inode - * gets freed after an RCU cycle, so the content will still + * gets freed after an SRCU cycle, so the content will still * be safe if the iteration is going on now. */ ti->flags &= ~TRACEFS_EVENT_INODE; --- a/fs/tracefs/internal.h +++ b/fs/tracefs/internal.h @@ -76,4 +76,7 @@ struct inode *tracefs_get_inode(struct s void eventfs_remount(struct tracefs_inode *ti, bool update_uid, bool update_gid); void eventfs_d_release(struct dentry *dentry); +int eventfs_remount_lock(void); +void eventfs_remount_unlock(int srcu_idx); + #endif /* _TRACEFS_INTERNAL_H */