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eventfs: Free all of the eventfs_inode after RCU

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The freeing of eventfs_inode via a kfree_rcu() callback. But the content
of the eventfs_inode was being freed after the last kref. This is
dangerous, as changes are being made that can access the content of an
eventfs_inode from an RCU loop.

Instead of using kfree_rcu() use call_rcu() that calls a function to do
all the freeing of the eventfs_inode after a RCU grace period has expired.

Link: https://lore.kernel.org/linux-trace-kernel/20240502200905.370261163@goodmis.org

Cc: stable@vger.kernel.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Fixes: 43aa6f97c2 ("eventfs: Get rid of dentry pointers without refcounts")
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt (Google) 2024-05-02 16:08:22 -04:00
parent b63db58e2f
commit ee4e037947
1 changed files with 16 additions and 9 deletions
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25
fs/tracefs/event_inode.c
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@ -73,6 +73,21 @@ enum {
#define EVENTFS_MODE_MASK (EVENTFS_SAVE_MODE - 1)
static void free_ei_rcu(struct rcu_head *rcu)
{
struct eventfs_inode *ei = container_of(rcu, struct eventfs_inode, rcu);
struct eventfs_root_inode *rei;
kfree(ei->entry_attrs);
kfree_const(ei->name);
if (ei->is_events) {
rei = get_root_inode(ei);
kfree(rei);
} else {
kfree(ei);
}
}
/*
* eventfs_inode reference count management.
*
@ -85,7 +100,6 @@ static void release_ei(struct kref *ref)
{
struct eventfs_inode *ei = container_of(ref, struct eventfs_inode, kref);
const struct eventfs_entry *entry;
struct eventfs_root_inode *rei;
WARN_ON_ONCE(!ei->is_freed);
@ -95,14 +109,7 @@ static void release_ei(struct kref *ref)
entry->release(entry->name, ei->data);
}
kfree(ei->entry_attrs);
kfree_const(ei->name);
if (ei->is_events) {
rei = get_root_inode(ei);
kfree_rcu(rei, ei.rcu);
} else {
kfree_rcu(ei, rcu);
}
call_rcu(&ei->rcu, free_ei_rcu);
}
static inline void put_ei(struct eventfs_inode *ei)