Message-ID: <4CEBD715.3070405@redhat.com>
Date:	Tue, 23 Nov 2010 09:00:37 -0600
From:	Eric Sandeen <sandeen@...hat.com>
To:	Nick Piggin <npiggin@...nel.dk>
CC:	linux-ext4@...r.kernel.org, zeng.zhaoming@...escale.com
Subject: Re: [bug] ext4 bug

On 11/23/10 3:32 AM, Nick Piggin wrote:
> Hi,
> 
> Got a couple of ext4 bugs. modprobe ext4 ; # use it ; rmmod ext4 ;
> modprobe ext4 reproduced it twice.
> 
> Seems to not deallocate the kobject stuff properly, and then probably
> something in an error path is doing a double free and corrupting stuff.

have a look at
http://www.spinics.net/lists/linux-ext4/msg21890.html

> ext4 allocate memory for cache name by:
>     namep = kstrdup(name, GFP_KERNEL);
> and reclaim it by:
>     name = kmem_cache_name(cache);
>     kfree(name)
> 
> This is ok if allocator only reference to the cache name memory, and return
> the name memory pass to kmem_cache_create() by kmem_cache_name();
> But not true in slub, when using slub, memory leak and double free error appears.

-Eric

> 
> [ 1234.475241]
> =============================================================================
> [ 1234.475503] BUG kmalloc-32: Object already free
> [ 1234.475665]
> -----------------------------------------------------------------------------
> [ 1234.475668] 
> [ 1234.476076] INFO: Allocated in kmem_cache_create+0x65/0x2d0
> age=1104271 cpu=0 pid=1492
> [ 1234.476332] INFO: Freed in kmem_cache_release+0x16/0x30 age=1 cpu=13
> pid=27603
> [ 1234.476584] INFO: Slab 0xffffea0003cf5cd8 objects=39 used=9
> fp=0xffff880116acd750 flags=0x40000000000000c1
> [ 1234.476842] INFO: Object 0xffff880116acd6e8 @offset=1768
> fp=0xffff880116acd478
> [ 1234.476845] 
> [ 1234.477244] Bytes b4 0xffff880116acd6d8:  00 00 00 00 00 00 00 00 5a
> 5a 5a 5a 5a 5a 5a 5a ........ZZZZZZZZ
> [ 1234.478696]   Object 0xffff880116acd6e8:  6b 6b 6b 6b 6b 6b 6b 6b 6b
> 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk
> [ 1234.480152]   Object 0xffff880116acd6f8:  6b 6b 6b 6b 6b 6b 6b 6b 6b
> 6b 6b 6b 6b 6b 6b a5 kkkkkkkkkkkkkkk?
> [ 1234.481604]  Redzone 0xffff880116acd708:  bb bb bb bb bb bb bb bb
> ????????        
> [ 1234.483059]  Padding 0xffff880116acd748:  5a 5a 5a 5a 5a 5a 5a 5a
> ZZZZZZZZ        
> [ 1234.484512] Pid: 27603, comm: rmmod Not tainted 2.6.37-rc3+ #27
> [ 1234.484679] Call Trace:
> [ 1234.484837]  [<ffffffff8110bb1e>] print_trailer+0xfe/0x160
> [ 1234.485025]  [<ffffffffa00626a7>] ? ext4_exit_mballoc+0x67/0x80
> [ext4]
> [ 1234.485196]  [<ffffffff8110bbbc>] object_err+0x3c/0x50
> [ 1234.485362]  [<ffffffff8110e015>] free_debug_processing+0x1f5/0x250
> [ 1234.485546]  [<ffffffffa00626a7>] ? ext4_exit_mballoc+0x67/0x80
> [ext4]
> [ 1234.485719]  [<ffffffff8110e5d4>] __slab_free+0x1b4/0x1e0
> [ 1234.485891]  [<ffffffff8110e71c>] kfree+0x11c/0x1c0
> [ 1234.486071]  [<ffffffffa00626a7>] ? ext4_exit_mballoc+0x67/0x80
> [ext4]
> [ 1234.486258]  [<ffffffffa00626a7>] ext4_exit_mballoc+0x67/0x80 [ext4]
> [ 1234.486444]  [<ffffffffa0070e23>] ext4_exit_fs+0xfb/0x12e [ext4]
> [ 1234.486619]  [<ffffffff81083b4d>] ? trace_hardirqs_on+0xd/0x10
> [ 1234.486791]  [<ffffffff810904ea>] sys_delete_module+0x17a/0x270
> [ 1234.486964]  [<ffffffff816036ad>] ? retint_swapgs+0xe/0x13
> [ 1234.487133]  [<ffffffff81083afd>] ?
> trace_hardirqs_on_caller+0x13d/0x180
> [ 1234.487306]  [<ffffffff8100312b>] system_call_fastpath+0x16/0x1b
> [ 1234.487477] FIX kmalloc-32: Object at 0xffff880116acd6e8 not freed
> [ 1243.592427] ------------[ cut here ]------------
> [ 1243.592595] WARNING: at fs/sysfs/dir.c:451 sysfs_add_one+0xce/0x200()
> [ 1243.592757] Hardware name: S5520UR
> [ 1243.592921] sysfs: cannot create duplicate filename '/fs/ext4'
> [ 1243.593081] Modules linked in: ext4(+) jbd2 crc16 brd [last unloaded:
> ext4]
> [ 1243.593642] Pid: 27865, comm: modprobe Not tainted 2.6.37-rc3+ #27
> [ 1243.593800] Call Trace:
> [ 1243.593964]  [<ffffffff810497ea>] warn_slowpath_common+0x7a/0xb0
> [ 1243.594129]  [<ffffffff810498c1>] warn_slowpath_fmt+0x41/0x50
> [ 1243.594289]  [<ffffffff8118c35e>] sysfs_add_one+0xce/0x200
> [ 1243.594447]  [<ffffffff8118c50c>] create_dir+0x7c/0xd0
> [ 1243.594607]  [<ffffffff8118c5dc>] sysfs_create_dir+0x7c/0xd0
> [ 1243.594771]  [<ffffffff8127949b>] kobject_add_internal+0xab/0x1f0
> [ 1243.594954]  [<ffffffff8127960f>] kset_register+0x2f/0x60
> [ 1243.595118]  [<ffffffff81279c9f>] kset_create_and_add+0x8f/0x1c0
> [ 1243.595287]  [<ffffffffa00ff11e>] ? ext4_init_fs+0x0/0x139 [ext4]
> [ 1243.595454]  [<ffffffffa00ff15a>] ext4_init_fs+0x3c/0x139 [ext4]
> [ 1243.595617]  [<ffffffff810001de>] do_one_initcall+0x3e/0x180
> [ 1243.595780]  [<ffffffff81093ba2>] sys_init_module+0xb2/0x200
> [ 1243.595949]  [<ffffffff8100312b>] system_call_fastpath+0x16/0x1b
> [ 1243.596113] ---[ end trace 8766368be9c85c43 ]---
> [ 1243.596279] kobject_add_internal failed for ext4 with -EEXIST, don't
> try to register things with the same name in the same directory.
> [ 1243.596538] Pid: 27865, comm: modprobe Tainted: G        W
> 2.6.37-rc3+ #27
> [ 1243.596711] Call Trace:
> [ 1243.596865]  [<ffffffff8127953c>] kobject_add_internal+0x14c/0x1f0
> [ 1243.597043]  [<ffffffff8127960f>] kset_register+0x2f/0x60
> [ 1243.597208]  [<ffffffff81279c9f>] kset_create_and_add+0x8f/0x1c0
> [ 1243.597377]  [<ffffffffa00ff11e>] ? ext4_init_fs+0x0/0x139 [ext4]
> [ 1243.597545]  [<ffffffffa00ff15a>] ext4_init_fs+0x3c/0x139 [ext4]
> [ 1243.597710]  [<ffffffff810001de>] do_one_initcall+0x3e/0x180
> [ 1243.597872]  [<ffffffff81093ba2>] sys_init_module+0xb2/0x200
> [ 1243.598085]  [<ffffffff8100312b>] system_call_fastpath+0x16/0x1b
> 
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