| Message ID | 20190404003249.14356-28-matthewgarrett@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Lockdown patches for 5.2 | expand |
On Wed, 3 Apr 2019 17:32:49 -0700 Matthew Garrett <matthewgarrett@google.com> wrote: > +static void tracefs_destroy_inode(struct inode *inode) > +{ > + if S_ISREG(inode->i_mode) Can we please put parenthesis around the condition. I know that the macro has them, but no other place in the kernel plays such a trick. if (S_ISREG(inode->i_mode)) Other than that, the rest looks good. Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org> -- Steve > + kfree(inode->i_fop); > +} > + > static int tracefs_remount(struct super_block *sb, int *flags, char *data) > { > int err; > @@ -260,6 +288,7 @@ static int tracefs_show_options(struct seq_file *m, struct dentry *root) > > static const struct super_operations tracefs_super_operations = { > .statfs = simple_statfs, > + .destroy_inode = tracefs_destroy_inode, > .remount_fs = tracefs_remount, > .show_options = tracefs_show_options, > }; > @@ -393,6 +422,7 @@ struct dentry *tracefs_create_file(const char *name, umode_t mode, > { > struct dentry *dentry; > struct inode *inode; > + struct file_operations *proxy_fops; > > if (!(mode & S_IFMT)) > mode |= S_IFREG; > @@ -406,8 +436,16 @@ struct dentry *tracefs_create_file(const char *name, umode_t mode, > if (unlikely(!inode)) > return failed_creating(dentry); > > + proxy_fops = kzalloc(sizeof(struct file_operations), GFP_KERNEL); > + if (!proxy_fops) > + return failed_creating(dentry); > + > + dentry->d_fsdata = fops ? (void *)fops : > + (void *)&tracefs_file_operations; > + memcpy(proxy_fops, dentry->d_fsdata, sizeof(struct file_operations)); > + proxy_fops->open = default_open_file; > inode->i_mode = mode; > - inode->i_fop = fops ? fops : &tracefs_file_operations; > + inode->i_fop = proxy_fops; > inode->i_private = data; > d_instantiate(dentry, inode); > fsnotify_create(dentry->d_parent->d_inode, dentry);
On Thu, Apr 4, 2019 at 6:39 AM Steven Rostedt <rostedt@goodmis.org> wrote: > > On Wed, 3 Apr 2019 17:32:49 -0700 > Matthew Garrett <matthewgarrett@google.com> wrote: > > > > +static void tracefs_destroy_inode(struct inode *inode) > > +{ > > + if S_ISREG(inode->i_mode) > > Can we please put parenthesis around the condition. I know that the > macro has them, but no other place in the kernel plays such a trick. Ha, I've been spending too much time in Go lately. Fixed.
diff --git a/fs/tracefs/inode.c b/fs/tracefs/inode.c index 7098c49f3693..576327ffd9d1 100644 --- a/fs/tracefs/inode.c +++ b/fs/tracefs/inode.c @@ -31,6 +31,21 @@ static struct vfsmount *tracefs_mount; static int tracefs_mount_count; static bool tracefs_registered; +static int default_open_file(struct inode *inode, struct file *filp) +{ + struct dentry *dentry = filp->f_path.dentry; + struct file_operations *real_fops; + + if (!dentry) + return -EINVAL; + + if (kernel_is_locked_down("tracefs", LOCKDOWN_CONFIDENTIALITY)) + return -EPERM; + + real_fops = dentry->d_fsdata; + return real_fops->open(inode, filp); +} + static ssize_t default_read_file(struct file *file, char __user *buf, size_t count, loff_t *ppos) { @@ -50,6 +65,13 @@ static const struct file_operations tracefs_file_operations = { .llseek = noop_llseek, }; +static const struct file_operations tracefs_proxy_file_operations = { + .read = default_read_file, + .write = default_write_file, + .open = default_open_file, + .llseek = noop_llseek, +}; + static struct tracefs_dir_ops { int (*mkdir)(const char *name); int (*rmdir)(const char *name); @@ -225,6 +247,12 @@ static int tracefs_apply_options(struct super_block *sb) return 0; } +static void tracefs_destroy_inode(struct inode *inode) +{ + if S_ISREG(inode->i_mode) + kfree(inode->i_fop); +} + static int tracefs_remount(struct super_block *sb, int *flags, char *data) { int err; @@ -260,6 +288,7 @@ static int tracefs_show_options(struct seq_file *m, struct dentry *root) static const struct super_operations tracefs_super_operations = { .statfs = simple_statfs, + .destroy_inode = tracefs_destroy_inode, .remount_fs = tracefs_remount, .show_options = tracefs_show_options, }; @@ -393,6 +422,7 @@ struct dentry *tracefs_create_file(const char *name, umode_t mode, { struct dentry *dentry; struct inode *inode; + struct file_operations *proxy_fops; if (!(mode & S_IFMT)) mode |= S_IFREG; @@ -406,8 +436,16 @@ struct dentry *tracefs_create_file(const char *name, umode_t mode, if (unlikely(!inode)) return failed_creating(dentry); + proxy_fops = kzalloc(sizeof(struct file_operations), GFP_KERNEL); + if (!proxy_fops) + return failed_creating(dentry); + + dentry->d_fsdata = fops ? (void *)fops : + (void *)&tracefs_file_operations; + memcpy(proxy_fops, dentry->d_fsdata, sizeof(struct file_operations)); + proxy_fops->open = default_open_file; inode->i_mode = mode; - inode->i_fop = fops ? fops : &tracefs_file_operations; + inode->i_fop = proxy_fops; inode->i_private = data; d_instantiate(dentry, inode); fsnotify_create(dentry->d_parent->d_inode, dentry);
Tracefs may release more information about the kernel than desirable, so restrict it when the kernel is locked down in confidentiality mode by preventing open(). Signed-off-by: Matthew Garrett <mjg59@google.com> Cc: Steven Rostedt <rostedt@goodmis.org> --- fs/tracefs/inode.c | 40 +++++++++++++++++++++++++++++++++++++++- 1 file changed, 39 insertions(+), 1 deletion(-)