Date:   Thu, 17 Aug 2017 11:24:34 +0200
From:   Stefano Brivio <sbrivio@...hat.com>
To:     Jeff Kirsher <jeffrey.t.kirsher@...el.com>,
        "David S . Miller" <davem@...emloft.net>
Cc:     netdev@...r.kernel.org, intel-wired-lan@...ts.osuosl.org,
        Alan Brady <alan.brady@...el.com>,
        Stefan Assmann <sassmann@...hat.com>
Subject: Re: [PATCH] i40e{,vf}: Fix out-of-bound cpumask read in IRQ
 affinity handler

Jeff, Dave,

This is a pretty bad issue as one can crash a kernel quite easily by
forcing interrupt affinity changes.

We now have three versions of this patch, with exactly the same code
changes. I posted mine as I independently found this issue last week
and didn't notice Juergen patch which was posted two days earlier.

I didn't notice the other patch in the pull request from Jeff either, I
just checked his tree and it wasn't there until yesterday. Frankly
speaking, I think this was quite vaguely worded and hidden in the cover
letter, and queued up for net-next, while it should really go to net as
it fixes a panic in mainline.

FWIW, I don't care too much about which version ends up applied, even
though I'd prefer one which a commit message which clearly describes
the issue with its implications and reports the right Fixed: tag. Both
my patch and Juergen's v2, posted later, are fine by me (I still think
mine is a bit clearer).

--
Stefano

On Tue, 15 Aug 2017 12:30:14 +0200
Stefano Brivio <sbrivio@...hat.com> wrote:

> The cpumask used in i40e{,vf}_irq_affinity_notify() is allocated
> by irq_affinity_notify() with alloc_cpumask_var(), which doesn't
> allocate NR_CPUS bits, but only nr_cpumask_bits bits. If we just
> dereference it, we'll read way more than what is allocated, e.g.
> 1024 bytes vs. 8 bytes allocated on x86_64 machine with 24 CPUs.
> 
> Use cpumask_copy() instead. A comprehensive explanation is given
> in the comments about cpumask_var_t, in include/linux/cpumask.h.
> 
> KASAN reports:
> [   25.242312] BUG: KASAN: slab-out-of-bounds in i40e_irq_affinity_notify+0x30/0x50 [i40e] at addr ffff880462eea960
> [   25.242315] Read of size 1024 by task kworker/2:1/170
> [   25.242322] CPU: 2 PID: 170 Comm: kworker/2:1 Not tainted 4.11.0-22.el7a.x86_64 #1
> [   25.242325] Hardware name: HP ProLiant DL380 Gen9, BIOS P89 05/06/2015
> [   25.242336] Workqueue: events irq_affinity_notify
> [   25.242340] Call Trace:
> [   25.242350]  dump_stack+0x63/0x8d
> [   25.242358]  kasan_object_err+0x21/0x70
> [   25.242364]  kasan_report+0x288/0x540
> [   25.242397]  ? i40e_irq_affinity_notify+0x30/0x50 [i40e]
> [   25.242403]  check_memory_region+0x13c/0x1a0
> [   25.242408]  __asan_loadN+0xf/0x20
> [   25.242440]  i40e_irq_affinity_notify+0x30/0x50 [i40e]
> [   25.242446]  irq_affinity_notify+0x1b4/0x230
> [   25.242452]  ? irq_set_affinity_notifier+0x130/0x130
> [   25.242457]  ? kasan_slab_free+0x89/0xc0
> [   25.242466]  process_one_work+0x32f/0x6f0
> [   25.242472]  worker_thread+0x89/0x770
> [   25.242481]  ? pci_mmcfg_check_reserved+0xc0/0xc0
> [   25.242488]  kthread+0x18c/0x1e0
> [   25.242493]  ? process_one_work+0x6f0/0x6f0
> [   25.242499]  ? kthread_create_on_node+0xc0/0xc0
> [   25.242506]  ret_from_fork+0x2c/0x40
> [   25.242511] Object at ffff880462eea960, in cache kmalloc-8 size: 8
> [   25.242513] Allocated:
> [   25.242514] PID = 170
> [   25.242522]  save_stack_trace+0x1b/0x20
> [   25.242529]  save_stack+0x46/0xd0
> [   25.242533]  kasan_kmalloc+0xad/0xe0
> [   25.242537]  __kmalloc_node+0x12c/0x2b0
> [   25.242542]  alloc_cpumask_var_node+0x3c/0x60
> [   25.242546]  alloc_cpumask_var+0xe/0x10
> [   25.242550]  irq_affinity_notify+0x94/0x230
> [   25.242555]  process_one_work+0x32f/0x6f0
> [   25.242559]  worker_thread+0x89/0x770
> [   25.242564]  kthread+0x18c/0x1e0
> [   25.242568]  ret_from_fork+0x2c/0x40
> [   25.242569] Freed:
> [   25.242570] PID = 0
> [   25.242572] (stack is not available)
> [   25.242573] Memory state around the buggy address:
> [   25.242578]  ffff880462eea800: fc fc 00 fc fc 00 fc fc 00 fc fc 00 fc fc fb fc
> [   25.242582]  ffff880462eea880: fc fb fc fc fb fc fc 00 fc fc 00 fc fc 00 fc fc
> [   25.242586] >ffff880462eea900: 00 fc fc 00 fc fc 00 fc fc fb fc fc 00 fc fc fc
> [   25.242588]                                                           ^
> [   25.242592]  ffff880462eea980: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> [   25.242596]  ffff880462eeaa00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> [   25.242597] ==================================================================
> 
> Fixes: 96db776a3682 ("i40e/i40evf: fix interrupt affinity bug")
> Signed-off-by: Stefano Brivio <sbrivio@...hat.com>
> ---
> This should be considered for -stable, back to 4.10.
> 
>  drivers/net/ethernet/intel/i40e/i40e_main.c     | 2 +-
>  drivers/net/ethernet/intel/i40evf/i40evf_main.c | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/ethernet/intel/i40e/i40e_main.c b/drivers/net/ethernet/intel/i40e/i40e_main.c
> index 2db93d3f6d23..c0e42d162c7c 100644
> --- a/drivers/net/ethernet/intel/i40e/i40e_main.c
> +++ b/drivers/net/ethernet/intel/i40e/i40e_main.c
> @@ -3495,7 +3495,7 @@ static void i40e_irq_affinity_notify(struct irq_affinity_notify *notify,
>  	struct i40e_q_vector *q_vector =
>  		container_of(notify, struct i40e_q_vector, affinity_notify);
>  
> -	q_vector->affinity_mask = *mask;
> +	cpumask_copy(&q_vector->affinity_mask, mask);
>  }
>  
>  /**
> diff --git a/drivers/net/ethernet/intel/i40evf/i40evf_main.c b/drivers/net/ethernet/intel/i40evf/i40evf_main.c
> index 7c213a347909..a4b60367ecce 100644
> --- a/drivers/net/ethernet/intel/i40evf/i40evf_main.c
> +++ b/drivers/net/ethernet/intel/i40evf/i40evf_main.c
> @@ -520,7 +520,7 @@ static void i40evf_irq_affinity_notify(struct irq_affinity_notify *notify,
>  	struct i40e_q_vector *q_vector =
>  		container_of(notify, struct i40e_q_vector, affinity_notify);
>  
> -	q_vector->affinity_mask = *mask;
> +	cpumask_copy(&q_vector->affinity_mask, mask);
>  }
>  
>  /**

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