netdev - Re: [PATCH net-next] netlabel: fix out-of-bounds memory accesses

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Date:   Sun, 20 Mar 2022 17:55:02 -0400
From:   Paul Moore <paul@...l-moore.com>
To:     Wang Yufen <wangyufen@...wei.com>
Cc:     davem@...emloft.net, kuba@...nel.org, pabeni@...hat.com,
        netdev@...r.kernel.org, linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next] netlabel: fix out-of-bounds memory accesses

On Fri, Mar 18, 2022 at 2:17 AM Wang Yufen <wangyufen@...wei.com> wrote:
>
> In calipso_map_cat_ntoh(), in the for loop, if the return value of
> netlbl_bitmap_walk() is equal to (net_clen_bits - 1), when
> netlbl_bitmap_walk() is called next time, out-of-bounds memory accesses
> of bitmap[byte_offset] occurs.
>
> The bug was found during fuzzing. The following is the fuzzing report
>  BUG: KASAN: slab-out-of-bounds in netlbl_bitmap_walk+0x3c/0xd0
>  Read of size 1 at addr ffffff8107bf6f70 by task err_OH/252
>
>  CPU: 7 PID: 252 Comm: err_OH Not tainted 5.17.0-rc7+ #17
>  Hardware name: linux,dummy-virt (DT)
>  Call trace:
>   dump_backtrace+0x21c/0x230
>   show_stack+0x1c/0x60
>   dump_stack_lvl+0x64/0x7c
>   print_address_description.constprop.0+0x70/0x2d0
>   __kasan_report+0x158/0x16c
>   kasan_report+0x74/0x120
>   __asan_load1+0x80/0xa0
>   netlbl_bitmap_walk+0x3c/0xd0
>   calipso_opt_getattr+0x1a8/0x230
>   calipso_sock_getattr+0x218/0x340
>   calipso_sock_getattr+0x44/0x60
>   netlbl_sock_getattr+0x44/0x80
>   selinux_netlbl_socket_setsockopt+0x138/0x170
>   selinux_socket_setsockopt+0x4c/0x60
>   security_socket_setsockopt+0x4c/0x90
>   __sys_setsockopt+0xbc/0x2b0
>   __arm64_sys_setsockopt+0x6c/0x84
>   invoke_syscall+0x64/0x190
>   el0_svc_common.constprop.0+0x88/0x200
>   do_el0_svc+0x88/0xa0
>   el0_svc+0x128/0x1b0
>   el0t_64_sync_handler+0x9c/0x120
>   el0t_64_sync+0x16c/0x170
>
> Reported-by: Hulk Robot <hulkci@...wei.com>
> Signed-off-by: Wang Yufen <wangyufen@...wei.com>
> ---
>  net/netlabel/netlabel_kapi.c | 2 ++
>  1 file changed, 2 insertions(+)

Looks good to me, thanks for catching this and submitting a fix.

Acked-by: Paul Moore <paul@...l-moore.com>

> diff --git a/net/netlabel/netlabel_kapi.c b/net/netlabel/netlabel_kapi.c
> index beb0e573266d..54c083003947 100644
> --- a/net/netlabel/netlabel_kapi.c
> +++ b/net/netlabel/netlabel_kapi.c
> @@ -885,6 +885,8 @@ int netlbl_bitmap_walk(const unsigned char *bitmap, u32 bitmap_len,
>         unsigned char bitmask;
>         unsigned char byte;
>
> +       if (offset >= bitmap_len)
> +               return -1;
>         byte_offset = offset / 8;
>         byte = bitmap[byte_offset];
>         bit_spot = offset;

-- 
paul-moore.com