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cgroup: initialize xattr before calling d_instantiate()

PATCH Applied Li Zefan 2 participants 2 messages May 14, 2013 cgroup

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Li Zefan

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PATCH 1/1 cgroup: initialize xattr before calling d_instantiate()

cgroup_create_file() calls d_instantiate(), which may decide to look at the xattrs on the file. Smack always does this and SELinux can be configured to do so.

But cgroup_add_file() didn't initialize xattrs before calling cgroup_create_file(), which finally leads to dereferencing NULL dentry->d_fsdata.

This bug has been there since cgroup xattr was introduced.

Cc <[email protected]> # 3.8.x
Reported-by Ivan Bulatovic <combuster-fd97jBR+K/[email protected]>
Reported-by Casey Schaufler <[email protected]>
Signed-off-by Li Zefan <[email protected]>
---
 kernel/cgroup.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)
kernel/cgroup.c +5 -4
index 2a99262..38b1365 100644
@@ -2699,13 +2699,14 @@ static int cgroup_add_file(struct cgroup *cgrp, struct cgroup_subsys *subsys,
 		goto out;
 	}
 
+	cfe->type = (void *)cft;
+	cfe->dentry = dentry;
+	dentry->d_fsdata = cfe;
+	simple_xattrs_init(&cfe->xattrs);
+
 	mode = cgroup_file_mode(cft);
 	error = cgroup_create_file(dentry, mode | S_IFREG, cgrp->root->sb);
 	if (!error) {
-		cfe->type = (void *)cft;
-		cfe->dentry = dentry;
-		dentry->d_fsdata = cfe;
-		simple_xattrs_init(&cfe->xattrs);
 		list_add_tail(&cfe->node, &parent->files);
 		cfe = NULL;
 	}
Signature · 1 line
1.8.0.2
maintainer Applied
#1 lore raw
Quoted 8 lines · Li Zefan

cgroup_create_file() calls d_instantiate(), which may decide to look at the xattrs on the file. Smack always does this and SELinux can be configured to do so.

But cgroup_add_file() didn't initialize xattrs before calling cgroup_create_file(), which finally leads to dereferencing NULL dentry->d_fsdata.

Quoted 6 lines

This bug has been there since cgroup xattr was introduced.

Cc <[email protected]> # 3.8.x
Reported-by Ivan Bulatovic <combuster-fd97jBR+K/[email protected]>
Reported-by Casey Schaufler <[email protected]>
Signed-off-by Li Zefan <[email protected]>

Applied to cgroup/for-3.10-fixes.

Thanks.

Signature · 1 line
tejun