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SubjectRe: [RFC] Changes to the LSM file-related hooks for 2.5.58

"Andi Kleen" <ak@muc.de> writes:
> Adding release_private_file requires fixing all code that uses
> init_private_file (including possible third party code). Otherwise
> you have some subtle leak. It would better to rename init_private_file to
> some other name and add appropiate comments so that this can be catched
> easily at compile time.

Thanks for the suggestion. I've split out this logical change into a
separate patch and reworked it in accordance with your suggestion. See
below. Let me know if this does not address your concern.

fs/exportfs/expfs.c | 5 ++---
fs/file_table.c | 33 ++++++++++++++++++++++++++-------
fs/nfsd/vfs.c | 5 ++---
include/linux/fs.h | 5 ++++-
kernel/ksyms.c | 3 ++-
5 files changed, 36 insertions(+), 15 deletions(-)
-----

===== fs/file_table.c 1.16 vs edited =====
--- 1.16/fs/file_table.c Tue Nov 26 14:29:39 2002
+++ edited/fs/file_table.c Wed Jan 15 09:39:17 2003
@@ -93,11 +93,13 @@

/*
* Clear and initialize a (private) struct file for the given dentry,
- * and call the open function (if any). The caller must verify that
- * inode->i_fop is not NULL.
+ * allocate the security structure, and call the open function (if any). The
+ * caller must verify that inode->i_fop is not NULL. The file should
+ * be released using close_private_file.
*/
-int init_private_file(struct file *filp, struct dentry *dentry, int mode)
+int open_private_file(struct file *filp, struct dentry *dentry, int mode)
{
+ int error;
memset(filp, 0, sizeof(*filp));
eventpoll_init_file(filp);
filp->f_mode = mode;
@@ -106,10 +108,27 @@
filp->f_uid = current->fsuid;
filp->f_gid = current->fsgid;
filp->f_op = dentry->d_inode->i_fop;
- if (filp->f_op->open)
- return filp->f_op->open(dentry->d_inode, filp);
- else
- return 0;
+ error = security_file_alloc(filp);
+ if (!error)
+ if (filp->f_op->open) {
+ error = filp->f_op->open(dentry->d_inode, filp);
+ if (error)
+ security_file_free(filp);
+ }
+ return error;
+}
+
+/*
+ * Release a private file by calling the release function (if any) and
+ * freeing the security structure.
+ */
+void close_private_file(struct file *file)
+{
+ struct inode * inode = file->f_dentry->d_inode;
+
+ if (file->f_op && file->f_op->release)
+ file->f_op->release(inode, file);
+ security_file_free(file);
}

void fput(struct file * file)
===== fs/exportfs/expfs.c 1.9 vs edited =====
--- 1.9/fs/exportfs/expfs.c Thu Oct 10 19:07:34 2002
+++ edited/fs/exportfs/expfs.c Wed Jan 15 09:38:53 2003
@@ -353,7 +353,7 @@
/*
* Open the directory ...
*/
- error = init_private_file(&file, dentry, FMODE_READ);
+ error = open_private_file(&file, dentry, FMODE_READ);
if (error)
goto out;
error = -EINVAL;
@@ -381,8 +381,7 @@
}

out_close:
- if (file.f_op->release)
- file.f_op->release(dir, &file);
+ close_private_file(&file);
out:
return error;
}
===== fs/nfsd/vfs.c 1.55 vs edited =====
--- 1.55/fs/nfsd/vfs.c Fri Jan 10 20:00:12 2003
+++ edited/fs/nfsd/vfs.c Wed Jan 15 09:39:35 2003
@@ -468,7 +468,7 @@
DQUOT_INIT(inode);
}

- err = init_private_file(filp, dentry, mode);
+ err = open_private_file(filp, dentry, mode);
if (!err) {
filp->f_flags = flags;
filp->f_vfsmnt = fhp->fh_export->ex_mnt;
@@ -491,8 +491,7 @@
struct dentry *dentry = filp->f_dentry;
struct inode *inode = dentry->d_inode;

- if (filp->f_op->release)
- filp->f_op->release(inode, filp);
+ close_private_file(filp);
if (filp->f_mode & FMODE_WRITE)
put_write_access(inode);
}
===== include/linux/fs.h 1.210 vs edited =====
--- 1.210/include/linux/fs.h Wed Jan 8 15:37:23 2003
+++ edited/include/linux/fs.h Wed Jan 15 09:41:28 2003
@@ -492,7 +492,10 @@
#define get_file(x) atomic_inc(&(x)->f_count)
#define file_count(x) atomic_read(&(x)->f_count)

-extern int init_private_file(struct file *, struct dentry *, int);
+/* Initialize and open a private file and allocate its security structure. */
+extern int open_private_file(struct file *, struct dentry *, int);
+/* Release a private file and free its security structure. */
+extern void close_private_file(struct file *file);

#define MAX_NON_LFS ((1UL<<31) - 1)

===== kernel/ksyms.c 1.178 vs edited =====
--- 1.178/kernel/ksyms.c Mon Jan 13 04:24:04 2003
+++ edited/kernel/ksyms.c Wed Jan 15 09:41:47 2003
@@ -179,7 +179,8 @@
EXPORT_SYMBOL(end_buffer_io_sync);
EXPORT_SYMBOL(__mark_inode_dirty);
EXPORT_SYMBOL(get_empty_filp);
-EXPORT_SYMBOL(init_private_file);
+EXPORT_SYMBOL(open_private_file);
+EXPORT_SYMBOL(close_private_file);
EXPORT_SYMBOL(filp_open);
EXPORT_SYMBOL(filp_close);
EXPORT_SYMBOL(put_filp);




--
Stephen Smalley, NSA
sds@epoch.ncsc.mil

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