Messages in this thread | | | Date | Mon, 14 Sep 2009 10:57:03 +0300 | Subject | Re: [origin tree SLAB corruption] BUG kmalloc-64: Poison overwritten, INFO: Allocated in bdi_alloc_work+0x2b/0x100 age=175 cpu=1 pid=3514 | From | Pekka Enberg <> |
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* Eric Paris <eparis@redhat.com> wrote: >> On Sat, 2009-09-12 at 09:24 +0200, Ingo Molnar wrote: >> > James - i did not see a security pull request email from you in my >> > lkml folder so i created this new thread. -tip testing found the >> > easy crash below. It reverts cleanly so i went that easy route. >> > >> > At a really quick 10-seconds glance the crash happens because we >> > destroy the slab cache twice, if the sysctl is toggled twice? >> >> Something a lot worse than SELinux here. I added this exact code and >> got this warning. Something is wrong in the world of >> kmem_cache_destroy.....
Btw, the kmem_cache_destroy() bug Eric found is not in Linu's tree yet.
On Mon, Sep 14, 2009 at 10:16 AM, Ingo Molnar <mingo@elte.hu> wrote: > -tip testing just triggered another type of SLAB problem (this time > not apparently related to the security subsystem): > > BUG kmalloc-64: Poison overwritten > ----------------------------------------------------------------------------- > > INFO: 0xf498f6a0-0xf498f6a7. First byte 0x90 instead of 0x6b > INFO: Allocated in bdi_alloc_work+0x2b/0x100 age=175 cpu=1 pid=3514 > INFO: Freed in bdi_work_free+0x45/0x60 age=9 cpu=1 pid=3509 > INFO: Slab 0xc3257d84 objects=36 used=11 fp=0xf498f690 flags=0x400000c3 > INFO: Object 0xf498f690 @offset=1680 fp=0xf498fe00 > > Bytes b4 0xf498f680: ab 0d 00 00 9c 27 ff ff 5a 5a 5a 5a 5a 5a 5a 5a «....'ÿÿZZZZZZZZ > Object 0xf498f690: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk > Object 0xf498f6a0: 90 f3 98 f4 60 3c 11 c1 6b 6b 6b 6b 6b 6b 6b 6b .ó.ô`<.Ákkkkkkkk
This would be use-after-free in kmalloc-64 cache. Given the trace and the fact that bdi_work_alloc() got introduce recently, it seems more likely that fs/fs-writeback.c is to blame here. Jens, does the warning ring a bell to you?
> Object 0xf498f6b0: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk > Object 0xf498f6c0: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b a5 kkkkkkkkkkkkkkk¥ > Redzone 0xf498f6d0: bb bb bb bb »»»» > Padding 0xf498f6f8: 5a 5a 5a 5a 5a 5a 5a 5a ZZZZZZZZ > Pid: 3514, comm: sync Not tainted 2.6.31-tip-02343-gb432421-dirty #14071 > Call Trace: > [<c10e5b29>] print_trailer+0xf9/0x170 > [<c10e5c95>] check_bytes_and_report+0xf5/0x120 > [<c10e7129>] check_object+0x1e9/0x230 > [<c10e848d>] alloc_debug_processing+0xfd/0x1d0 > [<c111394b>] ? bdi_alloc_work+0x2b/0x100 > [<c10e8687>] __slab_alloc+0x127/0x330 > [<c111394b>] ? bdi_alloc_work+0x2b/0x100 > [<c111394b>] ? bdi_alloc_work+0x2b/0x100 > [<c10e8a43>] kmem_cache_alloc+0x1b3/0x1d0 > [<c111394b>] ? bdi_alloc_work+0x2b/0x100 > [<c111394b>] ? bdi_alloc_work+0x2b/0x100 > [<c11148a4>] ? bdi_writeback_all+0x34/0x190 > [<c111394b>] bdi_alloc_work+0x2b/0x100 > [<c194c6b2>] ? _spin_lock+0x72/0x90 > [<c11148e2>] bdi_writeback_all+0x72/0x190 > [<c107b3db>] ? mark_held_locks+0x6b/0xb0 > [<c194ab75>] ? __mutex_unlock_slowpath+0xf5/0x160 > [<c107b76c>] ? trace_hardirqs_on_caller+0x15c/0x1c0 > [<c1114a48>] sync_inodes_sb+0x48/0x70 > [<c1118b0b>] __sync_filesystem+0x7b/0x90 > [<c1118c13>] sync_filesystems+0xf3/0x140 > [<c1118cd7>] sys_sync+0x27/0x60 > [<c100344b>] sysenter_do_call+0x12/0x36 > FIX kmalloc-64: Restoring 0xf498f6a0-0xf498f6a7=0x6b > > Now, this might be an extended arm of the security related slab > troubles. (which seem to have been cured by the revert i posted > though.) > > This bug is not bisectable at all - it happened after 1000+ > successful random bootups. The mainline base for > 2.6.31-tip-02343-gb432421 is upstream commit 86d7101. > > Full bootlog and config attached. > > Ingo > > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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