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Subject[PATCH] binderfs: rework superblock destruction
Date
From: Al Viro <viro@zeniv.linux.org.uk>

So far we relied on
.put_super = binderfs_put_super()
to destroy info we stashed in sb->s_fs_info. But the current implementation of
binderfs_fill_super() leads to a memory leak in the rare circumstance that
d_make_root() fails because ->put_super() is only called when sb->s_root is
initialized. Fix this by removing ->put_super() and simply do all that work in
binderfs_kill_super().

Reported-by: Dongliang Mu <mudongliangabcd@gmail.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
---
I should note that I didn't have time to test this.
---
drivers/android/binderfs.c | 25 ++++++++++++-------------
1 file changed, 12 insertions(+), 13 deletions(-)

diff --git a/drivers/android/binderfs.c b/drivers/android/binderfs.c
index 588d753a7a19..6d896f75aab6 100644
--- a/drivers/android/binderfs.c
+++ b/drivers/android/binderfs.c
@@ -340,22 +340,10 @@ static int binderfs_show_options(struct seq_file *seq, struct dentry *root)
return 0;
}

-static void binderfs_put_super(struct super_block *sb)
-{
- struct binderfs_info *info = sb->s_fs_info;
-
- if (info && info->ipc_ns)
- put_ipc_ns(info->ipc_ns);
-
- kfree(info);
- sb->s_fs_info = NULL;
-}
-
static const struct super_operations binderfs_super_ops = {
.evict_inode = binderfs_evict_inode,
.show_options = binderfs_show_options,
.statfs = simple_statfs,
- .put_super = binderfs_put_super,
};

static inline bool is_binderfs_control_device(const struct dentry *dentry)
@@ -785,11 +773,22 @@ static int binderfs_init_fs_context(struct fs_context *fc)
return 0;
}

+static void binderfs_kill_super(struct super_block *sb)
+{
+ struct binderfs_info *info = sb->s_fs_info;
+
+ if (info && info->ipc_ns)
+ put_ipc_ns(info->ipc_ns);
+
+ kfree(info);
+ kill_litter_super(sb);
+}
+
static struct file_system_type binder_fs_type = {
.name = "binder",
.init_fs_context = binderfs_init_fs_context,
.parameters = binderfs_fs_parameters,
- .kill_sb = kill_litter_super,
+ .kill_sb = binderfs_kill_super,
.fs_flags = FS_USERNS_MOUNT,
};

--
2.34.1
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