Commit 9ce71148 authored by Josh Triplett's avatar Josh Triplett Committed by Linus Torvalds
Browse files

devpts: if initialization failed, don't crash when opening /dev/ptmx 



If devpts failed to initialize, it would store an ERR_PTR in the global
devpts_mnt.  A subsequent open of /dev/ptmx would call devpts_new_index,
which would dereference devpts_mnt and crash.

Avoid storing invalid values in devpts_mnt; leave it NULL instead.  Make
both devpts_new_index and devpts_pty_new fail gracefully with ENODEV in
that case, which then becomes the return value to the userspace open call
on /dev/ptmx.

[akpm@linux-foundation.org: remove unneeded static]
Signed-off-by: default avatarJosh Triplett <josh@joshtriplett.org>
Reported-by: default avatarFengguang Wu <fengguang.wu@intel.com>
Reviewed-by: default avatarPeter Hurley <peter@hurleysoftware.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 15f1d827

fs/devpts/inode.c

+24 −7
Original line number Diff line number Diff line
@@ -142,6 +142,8 @@ static inline struct super_block *pts_sb_from_inode(struct inode *inode) 
	if (inode->i_sb->s_magic == DEVPTS_SUPER_MAGIC)

		return inode->i_sb;

#endif

	if (!devpts_mnt)

		return NULL;

	return devpts_mnt->mnt_sb;

}
@@ -525,10 +527,14 @@ static struct file_system_type devpts_fs_type = { 
int devpts_new_index(struct inode *ptmx_inode)

{

	struct super_block *sb = pts_sb_from_inode(ptmx_inode);

	struct pts_fs_info *fsi = DEVPTS_SB(sb);

	struct pts_fs_info *fsi;

	int index;

	int ida_ret;



	if (!sb)

		return -ENODEV;



	fsi = DEVPTS_SB(sb);

retry:

	if (!ida_pre_get(&fsi->allocated_ptys, GFP_KERNEL))

		return -ENOMEM;
@@ -584,11 +590,18 @@ struct inode *devpts_pty_new(struct inode *ptmx_inode, dev_t device, int index, 
	struct dentry *dentry;

	struct super_block *sb = pts_sb_from_inode(ptmx_inode);

	struct inode *inode;

	struct dentry *root = sb->s_root;

	struct pts_fs_info *fsi = DEVPTS_SB(sb);

	struct pts_mount_opts *opts = &fsi->mount_opts;

	struct dentry *root;

	struct pts_fs_info *fsi;

	struct pts_mount_opts *opts;

	char s[12];



	if (!sb)

		return ERR_PTR(-ENODEV);



	root = sb->s_root;

	fsi = DEVPTS_SB(sb);

	opts = &fsi->mount_opts;



	inode = new_inode(sb);

	if (!inode)

		return ERR_PTR(-ENOMEM);
@@ -676,12 +689,16 @@ static int __init init_devpts_fs(void) 
	struct ctl_table_header *table;



	if (!err) {

		struct vfsmount *mnt;



		table = register_sysctl_table(pty_root_table);

		devpts_mnt = kern_mount(&devpts_fs_type);

		if (IS_ERR(devpts_mnt)) {

			err = PTR_ERR(devpts_mnt);

		mnt = kern_mount(&devpts_fs_type);

		if (IS_ERR(mnt)) {

			err = PTR_ERR(mnt);

			unregister_filesystem(&devpts_fs_type);

			unregister_sysctl_table(table);

		} else {

			devpts_mnt = mnt;

		}

	}

	return err;

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