linux/fs/pstore/internal.h
Kees Cook 3a7d2fd16c pstore: Solve lockdep warning by moving inode locks
Lockdep complains about a possible deadlock between mount and unlink
(which is technically impossible), but fixing this improves possible
future multiple-backend support, and keeps locking in the right order.

The lockdep warning could be triggered by unlinking a file in the
pstore filesystem:

  -> #1 (&sb->s_type->i_mutex_key#14){++++++}:
         lock_acquire+0xc9/0x220
         down_write+0x3f/0x70
         pstore_mkfile+0x1f4/0x460
         pstore_get_records+0x17a/0x320
         pstore_fill_super+0xa4/0xc0
         mount_single+0x89/0xb0
         pstore_mount+0x13/0x20
         mount_fs+0xf/0x90
         vfs_kern_mount+0x66/0x170
         do_mount+0x190/0xd50
         SyS_mount+0x90/0xd0
         entry_SYSCALL_64_fastpath+0x1c/0xb1

  -> #0 (&psinfo->read_mutex){+.+.+.}:
         __lock_acquire+0x1ac0/0x1bb0
         lock_acquire+0xc9/0x220
         __mutex_lock+0x6e/0x990
         mutex_lock_nested+0x16/0x20
         pstore_unlink+0x3f/0xa0
         vfs_unlink+0xb5/0x190
         do_unlinkat+0x24c/0x2a0
         SyS_unlinkat+0x16/0x30
         entry_SYSCALL_64_fastpath+0x1c/0xb1

  Possible unsafe locking scenario:

        CPU0                    CPU1
        ----                    ----
   lock(&sb->s_type->i_mutex_key#14);
                                lock(&psinfo->read_mutex);
                                lock(&sb->s_type->i_mutex_key#14);
   lock(&psinfo->read_mutex);

Reported-by: Marta Lofstedt <marta.lofstedt@intel.com>
Reported-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Kees Cook <keescook@chromium.org>
Acked-by: Namhyung Kim <namhyung@kernel.org>
2017-04-27 20:35:34 -07:00

35 lines
940 B
C

#ifndef __PSTORE_INTERNAL_H__
#define __PSTORE_INTERNAL_H__
#include <linux/types.h>
#include <linux/time.h>
#include <linux/pstore.h>
#ifdef CONFIG_PSTORE_FTRACE
extern void pstore_register_ftrace(void);
extern void pstore_unregister_ftrace(void);
#else
static inline void pstore_register_ftrace(void) {}
static inline void pstore_unregister_ftrace(void) {}
#endif
#ifdef CONFIG_PSTORE_PMSG
extern void pstore_register_pmsg(void);
extern void pstore_unregister_pmsg(void);
#else
static inline void pstore_register_pmsg(void) {}
static inline void pstore_unregister_pmsg(void) {}
#endif
extern struct pstore_info *psinfo;
extern void pstore_set_kmsg_bytes(int);
extern void pstore_get_records(int);
extern void pstore_get_backend_records(struct pstore_info *psi,
struct dentry *root, int quiet);
extern int pstore_mkfile(struct dentry *root,
struct pstore_record *record);
extern bool pstore_is_mounted(void);
#endif