ext4 object already free.

From: Dave Jones
Date: Fri Mar 29 2013 - 11:59:09 EST


Just hit this very quickly after boot while fuzzing.
(top of tree is 0776ce03b1348d39ba3035ea3ee3d268a42912ce)

[ 93.602628] =============================================================================
[ 93.603689] BUG kmalloc-64 (Not tainted): Object already free
[ 93.604441] -----------------------------------------------------------------------------
[ 93.604441]
[ 93.605674] Disabling lock debugging due to kernel taint
[ 93.606377] INFO: Allocated in ext4_htree_store_dirent+0x34/0x120 age=3 cpu=2 pid=2120
[ 93.607400] __slab_alloc+0x44a/0x502
[ 93.607870] __kmalloc+0x323/0x3e0
[ 93.608330] ext4_htree_store_dirent+0x34/0x120
[ 93.608925] htree_dirblock_to_tree+0x169/0x1c0
[ 93.609526] ext4_htree_fill_tree+0x77/0x1e0
[ 93.610093] ext4_readdir+0x51c/0x820
[ 93.610586] vfs_readdir+0xb8/0xf0
[ 93.611046] sys_getdents+0x8f/0x120
[ 93.611528] system_call_fastpath+0x16/0x1b
[ 93.612085] INFO: Freed in free_rb_tree_fname+0x6c/0xd0 age=3 cpu=2 pid=2120
[ 93.612999] __slab_free+0x41/0x3a0
[ 93.613469] kfree+0x2ca/0x300
[ 93.613885] free_rb_tree_fname+0x6c/0xd0
[ 93.614420] ext4_release_dir+0x1e/0x30
[ 93.614935] __fput+0xf5/0x2d0
[ 93.615352] ____fput+0xe/0x10
[ 93.615769] task_work_run+0xa4/0xd0
[ 93.616251] do_notify_resume+0x71/0xb0
[ 93.616764] int_signal+0x12/0x17
[ 93.617212] INFO: Slab 0xffffea0002665f80 objects=20 used=12 fp=0xffff88009997fb90 flags=0x3000000000004081
[ 93.618457] INFO: Object 0xffff88009997e620 @offset=1568 fp=0xffff88009997f570
[ 93.618457]
[ 93.619575] Bytes b4 ffff88009997e610: fd ae ff ff 00 00 00 00 5a 5a 5a 5a 5a 5a 5a 5a ........ZZZZZZZZ
[ 93.620789] Object ffff88009997e620: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk
[ 93.621983] Object ffff88009997e630: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk
[ 93.623176] Object ffff88009997e640: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk
[ 93.624341] Object ffff88009997e650: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b a5 kkkkkkkkkkkkkkk.
[ 93.625505] Redzone ffff88009997e660: bb bb bb bb bb bb bb bb ........
[ 93.626594] Padding ffff88009997e7a0: 5a 5a 5a 5a 5a 5a 5a 5a ZZZZZZZZ
[ 93.627684] Pid: 1850, comm: trinity-child37 Tainted: G B 3.9.0-rc4+ #7
[ 93.628623] Call Trace:
[ 93.628943] [<ffffffff81199b74>] print_trailer+0x154/0x210
[ 93.629648] [<ffffffff81190014>] ? hugetlb_fault+0x494/0x6b0
[ 93.630373] [<ffffffff816bb538>] free_debug_processing+0x134/0x22b
[ 93.631164] [<ffffffff810b3b8e>] ? put_lock_stats.isra.27+0xe/0x40
[ 93.631955] [<ffffffff816c50e5>] ? _raw_spin_unlock_irqrestore+0x65/0x80
[ 93.632808] [<ffffffff812c20f1>] ? free_msg+0x21/0x40
[ 93.635318] [<ffffffff812c20f1>] ? free_msg+0x21/0x40
[ 93.637800] [<ffffffff816bb670>] __slab_free+0x41/0x3a0
[ 93.640304] [<ffffffff810b6ced>] ? trace_hardirqs_on+0xd/0x10
[ 93.642868] [<ffffffff816c50c2>] ? _raw_spin_unlock_irqrestore+0x42/0x80
[ 93.645524] [<ffffffff81355425>] ? debug_check_no_obj_freed+0x155/0x250
[ 93.648134] [<ffffffff8119d11d>] ? kfree+0x9d/0x300
[ 93.650521] [<ffffffff812c20f1>] ? free_msg+0x21/0x40
[ 93.652924] [<ffffffff8119d34a>] kfree+0x2ca/0x300
[ 93.655294] [<ffffffff8134a010>] ? delay_tsc+0x90/0xe0
[ 93.657696] [<ffffffff812c20f1>] free_msg+0x21/0x40
[ 93.660059] [<ffffffff812c289f>] freeque+0xcf/0x140
[ 93.662400] [<ffffffff812c2a93>] msgctl_down.constprop.9+0x183/0x200
[ 93.664918] [<ffffffff810767cf>] ? up_read+0x1f/0x40
[ 93.667261] [<ffffffff816c8f94>] ? __do_page_fault+0x214/0x5b0
[ 93.669717] [<ffffffff810b94be>] ? lock_release_non_nested+0x23e/0x320
[ 93.672257] [<ffffffff812c2da9>] sys_msgctl+0x139/0x400
[ 93.674641] [<ffffffff816c5d4d>] ? retint_swapgs+0xe/0x13
[ 93.677056] [<ffffffff810b6c55>] ? trace_hardirqs_on_caller+0x115/0x1a0
[ 93.679626] [<ffffffff8134b39e>] ? trace_hardirqs_on_thunk+0x3a/0x3f
[ 93.682159] [<ffffffff816cd942>] system_call_fastpath+0x16/0x1b
[ 93.799329] FIX kmalloc-64: Object at 0xffff88009997e620 not freed

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