netdev - Re: [PATCH] rhashtable: fix shift by 64 when shrinking

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Message-ID: <20160815060217.GA16182@gondor.apana.org.au>
Date:	Mon, 15 Aug 2016 14:02:17 +0800
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	Vegard Nossum <vegard.nossum@...cle.com>
Cc:	Thomas Graf <tgraf@...g.ch>, netdev@...r.kernel.org
Subject: Re: [PATCH] rhashtable: fix shift by 64 when shrinking

On Fri, Aug 12, 2016 at 08:10:44PM +0200, Vegard Nossum wrote:
> I got this:
> 
>     ================================================================================
>     UBSAN: Undefined behaviour in ./include/linux/log2.h:63:13
>     shift exponent 64 is too large for 64-bit type 'long unsigned int'
>     CPU: 1 PID: 721 Comm: kworker/1:1 Not tainted 4.8.0-rc1+ #87
>     Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.9.3-0-ge2fc41e-prebuilt.qemu-project.org 04/01/2014
>     Workqueue: events rht_deferred_worker
>      0000000000000000 ffff88011661f8d8 ffffffff82344f50 0000000041b58ab3
>      ffffffff84f98000 ffffffff82344ea4 ffff88011661f900 ffff88011661f8b0
>      0000000000000001 ffff88011661f6b8 dffffc0000000000 ffffffff867f7640
>     Call Trace:
>      [<ffffffff82344f50>] dump_stack+0xac/0xfc
>      [<ffffffff82344ea4>] ? _atomic_dec_and_lock+0xc4/0xc4
>      [<ffffffff8242f5b8>] ubsan_epilogue+0xd/0x8a
>      [<ffffffff82430c41>] __ubsan_handle_shift_out_of_bounds+0x255/0x29a
>      [<ffffffff824309ec>] ? __ubsan_handle_out_of_bounds+0x180/0x180
>      [<ffffffff84003436>] ? nl80211_req_set_reg+0x256/0x2f0
>      [<ffffffff812112ba>] ? print_context_stack+0x8a/0x160
>      [<ffffffff81200031>] ? amd_pmu_reset+0x341/0x380
>      [<ffffffff823af808>] rht_deferred_worker+0x1618/0x1790
>      [<ffffffff823af808>] ? rht_deferred_worker+0x1618/0x1790
>      [<ffffffff823ae1f0>] ? rhashtable_jhash2+0x370/0x370
>      [<ffffffff8134c12d>] ? process_one_work+0x6fd/0x1970
>      [<ffffffff8134c1cf>] process_one_work+0x79f/0x1970
>      [<ffffffff8134c12d>] ? process_one_work+0x6fd/0x1970
>      [<ffffffff8134ba30>] ? try_to_grab_pending+0x4c0/0x4c0
>      [<ffffffff8134d564>] ? worker_thread+0x1c4/0x1340
>      [<ffffffff8134d8ff>] worker_thread+0x55f/0x1340
>      [<ffffffff845e904f>] ? __schedule+0x4df/0x1d40
>      [<ffffffff8134d3a0>] ? process_one_work+0x1970/0x1970
>      [<ffffffff8134d3a0>] ? process_one_work+0x1970/0x1970
>      [<ffffffff813642f7>] kthread+0x237/0x390
>      [<ffffffff813640c0>] ? __kthread_parkme+0x280/0x280
>      [<ffffffff845f8c93>] ? _raw_spin_unlock_irq+0x33/0x50
>      [<ffffffff845f95df>] ret_from_fork+0x1f/0x40
>      [<ffffffff813640c0>] ? __kthread_parkme+0x280/0x280
>     ================================================================================
> 
> roundup_pow_of_two() is undefined when called with an argument of 0, so
> let's avoid the call and just fall back to ht->p.min_size (which should
> never be smaller than HASH_MIN_SIZE).
> 
> Cc: Herbert Xu <herbert@...dor.apana.org.au>
> Signed-off-by: Vegard Nossum <vegard.nossum@...cle.com>

Acked-by: Herbert Xu <herbert@...dor.apana.org.au>
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt