netdev - Re: [PATCH] net/mlx5: allocate enough space in

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Date:   Sun, 21 Oct 2018 13:56:26 +0300
From:   Or Gerlitz <gerlitz.or@...il.com>
To:     Dan Carpenter <dan.carpenter@...cle.com>
Cc:     Saeed Mahameed <saeedm@...lanox.com>,
        Paul Blakey <paulb@...lanox.com>,
        kernel-janitors@...r.kernel.org,
        Linux Netdev List <netdev@...r.kernel.org>,
        Leon Romanovsky <leonro@...lanox.com>
Subject: Re: [PATCH] net/mlx5: allocate enough space in

On Sat, Oct 20, 2018 at 11:37 PM Or Gerlitz <gerlitz.or@...il.com> wrote:
> On Fri, Oct 19, 2018 at 11:08 PM Dan Carpenter <dan.carpenter@...cle.com> wrote:
> > FDB_MAX_CHAIN is 3.  We wanted to allocate enough memory to hold four
> > structs but there are missing parentheses so we only allocate enough
> > memory for three structs and the first byte of the fourth one.
>
> yeah, seems that we were wrong here and the fix is correct, at some
> point I saw Kasan screams but it was gone later, let me look, thanks for pointing it out.

OK, here's the kasan note:

[  289.005141] BUG: KASAN: slab-out-of-bounds in
mlx5_init_fs+0x6a7/0x1176 [mlx5_core]
[  289.005244] Write of size 8 at addr ffff8806cfb70e58 by task modprobe/6186

my .config was like this w.r.t kasan:

CONFIG_KASAN_SHADOW_OFFSET=0xdffffc0000000000
CONFIG_HAVE_ARCH_KASAN=y
CONFIG_KASAN=y
# CONFIG_KASAN_EXTRA is not set
CONFIG_KASAN_OUTLINE=y
# CONFIG_KASAN_INLINE is not set
# CONFIG_TEST_KASAN is not set

where now, when I changed it to be:

CONFIG_KASAN_SHADOW_OFFSET=0xdffffc0000000000
CONFIG_HAVE_ARCH_KASAN=y
CONFIG_KASAN=y
CONFIG_KASAN_EXTRA=y
# CONFIG_KASAN_OUTLINE is not set
CONFIG_KASAN_INLINE=y
# CONFIG_TEST_KASAN is not set

Kasan is there to spot the bug.

I will re-post your patch, this time to netdev since the original
commit is there
and so should be the fix, thanks for reporting/fixing!

Or.