cc jejb@xxxxxxxxxxxxxxxxxx
On Mon, Aug 28, 2017 at 12:25 AM, Xin Long <lucien.xin@xxxxxxxxx> wrote:
> ChunYu found a kernel crash by syzkaller:
>
> [ 651.617875] kasan: CONFIG_KASAN_INLINE enabled
> [ 651.618217] kasan: GPF could be caused by NULL-ptr deref or user memory access
> [ 651.618731] general protection fault: 0000 [#1] SMP KASAN
> [ 651.621543] CPU: 1 PID: 9539 Comm: scsi Not tainted 4.11.0.cov #32
> [ 651.621938] Hardware name: Red Hat KVM, BIOS 0.5.1 01/01/2011
> [ 651.622309] task: ffff880117780000 task.stack: ffff8800a3188000
> [ 651.622762] RIP: 0010:skb_release_data+0x26c/0x590
> [...]
> [ 651.627260] Call Trace:
> [ 651.629156] skb_release_all+0x4f/0x60
> [ 651.629450] consume_skb+0x1a5/0x600
> [ 651.630705] netlink_unicast+0x505/0x720
> [ 651.632345] netlink_sendmsg+0xab2/0xe70
> [ 651.633704] sock_sendmsg+0xcf/0x110
> [ 651.633942] ___sys_sendmsg+0x833/0x980
> [ 651.637117] __sys_sendmsg+0xf3/0x240
> [ 651.638820] SyS_sendmsg+0x32/0x50
> [ 651.639048] entry_SYSCALL_64_fastpath+0x1f/0xc2
>
> It's caused by skb_shared_info at the end of sk_buff was overwritten by
> ISCSI_KEVENT_IF_ERROR when parsing nlmsg info from skb in iscsi_if_rx.
>
> During the loop if skb->len == nlh->nlmsg_len and both are sizeof(*nlh),
> ev = nlmsg_data(nlh) will acutally get skb_shinfo(SKB) instead and set a
> new value to skb_shinfo(SKB)->nr_frags by ev->type.
>
> This patch is to fix it by checking nlh->nlmsg_len properly there to
> avoid over accessing sk_buff.
>
> Reported-by: ChunYu Wang <chunwang@xxxxxxxxxx>
> Signed-off-by: Xin Long <lucien.xin@xxxxxxxxx>
> ---
> drivers/scsi/scsi_transport_iscsi.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/scsi/scsi_transport_iscsi.c b/drivers/scsi/scsi_transport_iscsi.c
> index e4b3d8f..bb4ed7b 100644
> --- a/drivers/scsi/scsi_transport_iscsi.c
> +++ b/drivers/scsi/scsi_transport_iscsi.c
> @@ -3697,7 +3697,7 @@ iscsi_if_rx(struct sk_buff *skb)
> uint32_t group;
>
> nlh = nlmsg_hdr(skb);
> - if (nlh->nlmsg_len < sizeof(*nlh) ||
> + if (nlh->nlmsg_len < sizeof(*nlh) + sizeof(*ev) ||
> skb->len < nlh->nlmsg_len) {
> break;
> }
> --
> 2.1.0
>
