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debugfs: fix create mutex racy fops and private data

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Setting fops and private data outside of the mutex at debugfs file
creation introduces a race where the files can be opened with the wrong
file operations and private data.  It is easy to trigger with a process
waiting on file creation notification.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: stable <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Mathieu Desnoyers 2009-11-17 14:40:26 -08:00 committed by Greg Kroah-Hartman
parent 18ef545e47
commit d3a3b0adad
1 changed files with 32 additions and 23 deletions
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55
fs/debugfs/inode.c
View file

@ -32,7 +32,9 @@ static struct vfsmount *debugfs_mount;
static int debugfs_mount_count; static int debugfs_mount_count;
static bool debugfs_registered; static bool debugfs_registered;
static struct inode *debugfs_get_inode(struct super_block *sb, int mode, dev_t dev) static struct inode *debugfs_get_inode(struct super_block *sb, int mode, dev_t dev,
void *data, const struct file_operations *fops)
{ {
struct inode *inode = new_inode(sb); struct inode *inode = new_inode(sb);
@ -44,14 +46,18 @@ static struct inode *debugfs_get_inode(struct super_block *sb, int mode, dev_t d
init_special_inode(inode, mode, dev); init_special_inode(inode, mode, dev);
break; break;
case S_IFREG: case S_IFREG:
inode->i_fop = &debugfs_file_operations; inode->i_fop = fops ? fops : &debugfs_file_operations;
inode->i_private = data;
break; break;
case S_IFLNK: case S_IFLNK:
inode->i_op = &debugfs_link_operations; inode->i_op = &debugfs_link_operations;
inode->i_fop = fops;
inode->i_private = data;
break; break;
case S_IFDIR: case S_IFDIR:
inode->i_op = &simple_dir_inode_operations; inode->i_op = &simple_dir_inode_operations;
inode->i_fop = &simple_dir_operations; inode->i_fop = fops ? fops : &simple_dir_operations;
inode->i_private = data;
/* directory inodes start off with i_nlink == 2 /* directory inodes start off with i_nlink == 2
* (for "." entry) */ * (for "." entry) */
@ -64,7 +70,8 @@ static struct inode *debugfs_get_inode(struct super_block *sb, int mode, dev_t d
/* SMP-safe */ /* SMP-safe */
static int debugfs_mknod(struct inode *dir, struct dentry *dentry, static int debugfs_mknod(struct inode *dir, struct dentry *dentry,
int mode, dev_t dev) int mode, dev_t dev, void *data,
const struct file_operations *fops)
{ {
struct inode *inode; struct inode *inode;
int error = -EPERM; int error = -EPERM;
@ -72,7 +79,7 @@ static int debugfs_mknod(struct inode *dir, struct dentry *dentry,
if (dentry->d_inode) if (dentry->d_inode)
return -EEXIST; return -EEXIST;
inode = debugfs_get_inode(dir->i_sb, mode, dev); inode = debugfs_get_inode(dir->i_sb, mode, dev, data, fops);
if (inode) { if (inode) {
d_instantiate(dentry, inode); d_instantiate(dentry, inode);
dget(dentry); dget(dentry);
@ -81,12 +88,13 @@ static int debugfs_mknod(struct inode *dir, struct dentry *dentry,
return error; return error;
} }
static int debugfs_mkdir(struct inode *dir, struct dentry *dentry, int mode) static int debugfs_mkdir(struct inode *dir, struct dentry *dentry, int mode,
void *data, const struct file_operations *fops)
{ {
int res; int res;
mode = (mode & (S_IRWXUGO | S_ISVTX)) | S_IFDIR; mode = (mode & (S_IRWXUGO | S_ISVTX)) | S_IFDIR;
res = debugfs_mknod(dir, dentry, mode, 0); res = debugfs_mknod(dir, dentry, mode, 0, data, fops);
if (!res) { if (!res) {
inc_nlink(dir); inc_nlink(dir);
fsnotify_mkdir(dir, dentry); fsnotify_mkdir(dir, dentry);
@ -94,18 +102,20 @@ static int debugfs_mkdir(struct inode *dir, struct dentry *dentry, int mode)
return res; return res;
} }
static int debugfs_link(struct inode *dir, struct dentry *dentry, int mode) static int debugfs_link(struct inode *dir, struct dentry *dentry, int mode,
void *data, const struct file_operations *fops)
{ {
mode = (mode & S_IALLUGO) | S_IFLNK; mode = (mode & S_IALLUGO) | S_IFLNK;
return debugfs_mknod(dir, dentry, mode, 0); return debugfs_mknod(dir, dentry, mode, 0, data, fops);
} }
static int debugfs_create(struct inode *dir, struct dentry *dentry, int mode) static int debugfs_create(struct inode *dir, struct dentry *dentry, int mode,
void *data, const struct file_operations *fops)
{ {
int res; int res;
mode = (mode & S_IALLUGO) | S_IFREG; mode = (mode & S_IALLUGO) | S_IFREG;
res = debugfs_mknod(dir, dentry, mode, 0); res = debugfs_mknod(dir, dentry, mode, 0, data, fops);
if (!res) if (!res)
fsnotify_create(dir, dentry); fsnotify_create(dir, dentry);
return res; return res;
@ -139,7 +149,9 @@ static struct file_system_type debug_fs_type = {
static int debugfs_create_by_name(const char *name, mode_t mode, static int debugfs_create_by_name(const char *name, mode_t mode,
struct dentry *parent, struct dentry *parent,
struct dentry **dentry) struct dentry **dentry,
void *data,
const struct file_operations *fops)
{ {
int error = 0; int error = 0;
@ -164,13 +176,16 @@ static int debugfs_create_by_name(const char *name, mode_t mode,
if (!IS_ERR(*dentry)) { if (!IS_ERR(*dentry)) {
switch (mode & S_IFMT) { switch (mode & S_IFMT) {
case S_IFDIR: case S_IFDIR:
error = debugfs_mkdir(parent->d_inode, *dentry, mode); error = debugfs_mkdir(parent->d_inode, *dentry, mode,
data, fops);
break; break;
case S_IFLNK: case S_IFLNK:
error = debugfs_link(parent->d_inode, *dentry, mode); error = debugfs_link(parent->d_inode, *dentry, mode,
data, fops);
break; break;
default: default:
error = debugfs_create(parent->d_inode, *dentry, mode); error = debugfs_create(parent->d_inode, *dentry, mode,
data, fops);
break; break;
} }
dput(*dentry); dput(*dentry);
@ -221,19 +236,13 @@ struct dentry *debugfs_create_file(const char *name, mode_t mode,
if (error) if (error)
goto exit; goto exit;
error = debugfs_create_by_name(name, mode, parent, &dentry); error = debugfs_create_by_name(name, mode, parent, &dentry,
data, fops);
if (error) { if (error) {
dentry = NULL; dentry = NULL;
simple_release_fs(&debugfs_mount, &debugfs_mount_count); simple_release_fs(&debugfs_mount, &debugfs_mount_count);
goto exit; goto exit;
} }
if (dentry->d_inode) {
if (data)
dentry->d_inode->i_private = data;
if (fops)
dentry->d_inode->i_fop = fops;
}
exit: exit:
return dentry; return dentry;
} }