linux-kernel - Can SLUB debugging show back-trace for deletion point?

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Message-ID: <4CAB60AB.5060808@candelatech.com>
Date:	Tue, 05 Oct 2010 10:30:19 -0700
From:	Ben Greear <greearb@...delatech.com>
To:	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Can SLUB debugging show back-trace for deletion point?

I'm debugging a wireless issue that is apparently a write-after-free
issue with skbs.

Oct  5 09:50:18 localhost kernel: =============================================================================
Oct  5 09:50:18 localhost kernel: BUG kmalloc-8192: Poison overwritten
Oct  5 09:50:18 localhost kernel: -----------------------------------------------------------------------------
Oct  5 09:50:18 localhost kernel:
Oct  5 09:50:18 localhost kernel: INFO: 0xf5b18040-0xf5b1812f. First byte 0x80 instead of 0x6b
Oct  5 09:50:18 localhost kernel: INFO: Allocated in ath_rxbuf_alloc+0x1d/0x74 [ath] age=54091 cpu=0 pid=613
Oct  5 09:50:18 localhost kernel: INFO: Freed in skb_release_data+0x8c/0x90 age=89 cpu=0 pid=4029
Oct  5 09:50:18 localhost kernel: INFO: Slab 0xc1fef300 objects=3 used=2 fp=0xf5b18000 flags=0x400040c1
Oct  5 09:50:18 localhost kernel: INFO: Object 0xf5b18000 @offset=0 fp=0x(null)
....

I get a backtrace for the point at which this is detected, but it seems what would
really be useful is a backtrace for where it was freed.

Is there any way to get that information printed out by slub debugging?

Thanks,
Ben

-- 
Ben Greear <greearb@...delatech.com>
Candela Technologies Inc  http://www.candelatech.com

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