cc [email protected]
On Mon, Aug 28, 2017 at 12:25 AM, Xin Long <[email protected]> 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 <[email protected]> > Signed-off-by: Xin Long <[email protected]> > --- > 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 >
