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Subject[PATCH 2/2] eventfs: Do not invalidate dentry in create_file/dir_dentry()
From: "Steven Rostedt (Google)" <rostedt@goodmis.org>

With the call to simple_recursive_removal() on the entire eventfs sub
system when the directory is removed, it performs the d_invalidate on all
the dentries when it is removed. There's no need to do clean ups when a
dentry is being created while the directory is being deleted.

As dentries are cleaned up by the simpler_recursive_removal(), trying to
do d_invalidate() in these functions will cause the dentry to be
invalidated twice, and crash the kernel.

Link: https://lore.kernel.org/all/20231116123016.140576-1-naresh.kamboju@linaro.org/

Fixes: 407c6726ca71 ("eventfs: Use simple_recursive_removal() to clean up dentries")
Reported-by: Mark Rutland <mark.rutland@arm.com>
Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Reported-by: Linux Kernel Functional Testing <lkft@linaro.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
fs/tracefs/event_inode.c | 19 ++++++-------------
1 file changed, 6 insertions(+), 13 deletions(-)

diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c
index f239b2b507a4..3eb6c622a74d 100644
--- a/fs/tracefs/event_inode.c
+++ b/fs/tracefs/event_inode.c
@@ -326,7 +326,6 @@ create_file_dentry(struct eventfs_inode *ei, int idx,
struct eventfs_attr *attr = NULL;
struct dentry **e_dentry = &ei->d_children[idx];
struct dentry *dentry;
- bool invalidate = false;

mutex_lock(&eventfs_mutex);
if (ei->is_freed) {
@@ -389,17 +388,14 @@ create_file_dentry(struct eventfs_inode *ei, int idx,
* Otherwise it means two dentries exist with the same name.
*/
WARN_ON_ONCE(!ei->is_freed);
- invalidate = true;
+ dentry = NULL;
}
mutex_unlock(&eventfs_mutex);

- if (invalidate)
- d_invalidate(dentry);
-
- if (lookup || invalidate)
+ if (lookup)
dput(dentry);

- return invalidate ? NULL : dentry;
+ return dentry;
}

/**
@@ -439,7 +435,6 @@ static struct dentry *
create_dir_dentry(struct eventfs_inode *pei, struct eventfs_inode *ei,
struct dentry *parent, bool lookup)
{
- bool invalidate = false;
struct dentry *dentry = NULL;

mutex_lock(&eventfs_mutex);
@@ -495,16 +490,14 @@ create_dir_dentry(struct eventfs_inode *pei, struct eventfs_inode *ei,
* Otherwise it means two dentries exist with the same name.
*/
WARN_ON_ONCE(!ei->is_freed);
- invalidate = true;
+ dentry = NULL;
}
mutex_unlock(&eventfs_mutex);
- if (invalidate)
- d_invalidate(dentry);

- if (lookup || invalidate)
+ if (lookup)
dput(dentry);

- return invalidate ? NULL : dentry;
+ return dentry;
}

/**
--
2.42.0

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