1f55c718c2
Considering current pty code and multiple devpts instances, it's possible to umount a devpts file system while a program still has /dev/tty opened pointing to a previosuly closed pty pair in that instance. In the case all ptmx and pts/N files are closed, umount can be done. If the program closes /dev/tty after umount is done, devpts_kill_index will use now an invalid super_block, which was already destroyed in the umount operation after running ->kill_sb. This is another "use after free" type of issue, but now related to the allocated super_block instance. To avoid the problem (warning at ida_remove and potential crashes) for this specific case, I added two functions in devpts which grabs additional references to the super_block, which pty code now uses so it makes sure the super block structure is still valid until pty shutdown is done. I also moved the additional inode references to the same functions, which also covered similar case with inode being freed before /dev/tty final close/shutdown. Signed-off-by: Herton R. Krzesinski <herton@redhat.com> Cc: stable@vger.kernel.org # 2.6.29+ Reviewed-by: Peter Hurley <peter@hurleysoftware.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
54 lines
1.6 KiB
C
54 lines
1.6 KiB
C
/* -*- linux-c -*- --------------------------------------------------------- *
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*
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* linux/include/linux/devpts_fs.h
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*
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* Copyright 1998-2004 H. Peter Anvin -- All Rights Reserved
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*
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* This file is part of the Linux kernel and is made available under
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* the terms of the GNU General Public License, version 2, or at your
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* option, any later version, incorporated herein by reference.
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*
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* ------------------------------------------------------------------------- */
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#ifndef _LINUX_DEVPTS_FS_H
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#define _LINUX_DEVPTS_FS_H
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#include <linux/errno.h>
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#ifdef CONFIG_UNIX98_PTYS
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int devpts_new_index(struct inode *ptmx_inode);
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void devpts_kill_index(struct inode *ptmx_inode, int idx);
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void devpts_add_ref(struct inode *ptmx_inode);
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void devpts_del_ref(struct inode *ptmx_inode);
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/* mknod in devpts */
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struct inode *devpts_pty_new(struct inode *ptmx_inode, dev_t device, int index,
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void *priv);
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/* get private structure */
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void *devpts_get_priv(struct inode *pts_inode);
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/* unlink */
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void devpts_pty_kill(struct inode *inode);
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#else
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/* Dummy stubs in the no-pty case */
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static inline int devpts_new_index(struct inode *ptmx_inode) { return -EINVAL; }
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static inline void devpts_kill_index(struct inode *ptmx_inode, int idx) { }
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static inline void devpts_add_ref(struct inode *ptmx_inode) { }
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static inline void devpts_del_ref(struct inode *ptmx_inode) { }
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static inline struct inode *devpts_pty_new(struct inode *ptmx_inode,
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dev_t device, int index, void *priv)
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{
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return ERR_PTR(-EINVAL);
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}
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static inline void *devpts_get_priv(struct inode *pts_inode)
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{
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return NULL;
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}
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static inline void devpts_pty_kill(struct inode *inode) { }
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#endif
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#endif /* _LINUX_DEVPTS_FS_H */
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