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pstore: Solve lockdep warning by moving inode locks

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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>
This commit is contained in:
Kees Cook
2017-04-27 15:53:21 -07:00
parent 041939c1ec
commit 3a7d2fd16c
3 changed files with 36 additions and 16 deletions
Download Patch File Download Diff File Expand all files Collapse all files

10
fs/pstore/platform.c
View File

@@ -810,17 +810,17 @@ static void decompress_record(struct pstore_record *record)
}
/*
* Read all the records from the persistent store. Create
* Read all the records from one persistent store backend. Create
* files in our filesystem. Don't warn about -EEXIST errors
* when we are re-scanning the backing store looking to add new
* error records.
*/
void pstore_get_records(int quiet)
void pstore_get_backend_records(struct pstore_info *psi,
struct dentry *root, int quiet)
{
struct pstore_info *psi = psinfo;
int failed = 0;
if (!psi)
if (!psi || !root)
return;
mutex_lock(&psi->read_mutex);
@@ -850,7 +850,7 @@ void pstore_get_records(int quiet)
break;
decompress_record(record);
rc = pstore_mkfile(record);
rc = pstore_mkfile(root, record);
if (rc) {
/* pstore_mkfile() did not take record, so free it. */
kfree(record->buf);