6.6-stable review patch. If anyone has any objections, please let me know.
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From: Steven Rostedt (Google) rostedt@goodmis.org
[ Upstream commit ee4e0379475e4fe723986ae96293e465014fa8d9 ]
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....
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: 43aa6f97c2d03 ("eventfs: Get rid of dentry pointers without refcounts") Signed-off-by: Steven Rostedt (Google) rostedt@goodmis.org Signed-off-by: Sasha Levin sashal@kernel.org --- fs/tracefs/event_inode.c | 25 ++++++++++++++++--------- 1 file changed, 16 insertions(+), 9 deletions(-)
diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c index a598fec065684..fd111e10f04e4 100644 --- a/fs/tracefs/event_inode.c +++ b/fs/tracefs/event_inode.c @@ -72,6 +72,21 @@ 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. * @@ -84,7 +99,6 @@ 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);
@@ -94,14 +108,7 @@ 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)