From: David Carlier <devnexen@gmail.com> stable inclusion from stable-v6.6.140 commit ae9cd0b46b1890040006a2fc5e905c5d6053fd02 category: bugfix bugzilla: https://atomgit.com/openeuler/kernel/issues/9232 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- 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 <devnexen@gmail.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Tengda Wu <wutengda2@huawei.com> --- fs/tracefs/event_inode.c | 14 ++++++++++++++ fs/tracefs/inode.c | 5 ++++- fs/tracefs/internal.h | 3 +++ 3 files changed, 21 insertions(+), 1 deletion(-) diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c index 4190e6155044..f98315e91e99 100644 --- a/fs/tracefs/event_inode.c +++ b/fs/tracefs/event_inode.c @@ -310,6 +310,8 @@ static void eventfs_set_attrs(struct eventfs_inode *ei, bool update_uid, kuid_t { struct eventfs_inode *ei_child; + lockdep_assert_held(&eventfs_mutex); + /* Update events/<system>/<event> */ if (WARN_ON_ONCE(level > 3)) return; @@ -985,3 +987,15 @@ void eventfs_remove_events_dir(struct eventfs_inode *ei) 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); +} diff --git a/fs/tracefs/inode.c b/fs/tracefs/inode.c index 6b70965063d7..6c7b48770948 100644 --- a/fs/tracefs/inode.c +++ b/fs/tracefs/inode.c @@ -362,6 +362,7 @@ static int tracefs_apply_options(struct super_block *sb, bool remount) struct tracefs_mount_opts *opts = &fsi->mount_opts; struct tracefs_inode *ti; bool update_uid, update_gid; + int srcu_idx; umode_t tmp_mode; /* @@ -386,6 +387,7 @@ static int tracefs_apply_options(struct super_block *sb, bool remount) update_uid = opts->opts & BIT(Opt_uid); update_gid = opts->opts & BIT(Opt_gid); + srcu_idx = eventfs_remount_lock(); rcu_read_lock(); list_for_each_entry_rcu(ti, &tracefs_inodes, list) { if (update_uid) @@ -398,6 +400,7 @@ static int tracefs_apply_options(struct super_block *sb, bool remount) eventfs_remount(ti, update_uid, update_gid); } rcu_read_unlock(); + eventfs_remount_unlock(srcu_idx); } return 0; @@ -444,7 +447,7 @@ static int tracefs_drop_inode(struct inode *inode) * 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; diff --git a/fs/tracefs/internal.h b/fs/tracefs/internal.h index d83c2a25f288..a4a7f8431aff 100644 --- a/fs/tracefs/internal.h +++ b/fs/tracefs/internal.h @@ -76,4 +76,7 @@ struct inode *tracefs_get_inode(struct super_block *sb); 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 */ -- 2.34.1