From b42bf0f15cf70926f3a460e7517703fda6191ba7 Mon Sep 17 00:00:00 2001 From: Xin Long Date: Sun, 27 Aug 2017 20:25:26 +0800 Subject: [PATCH] scsi: scsi_transport_iscsi: fix the issue that iscsi_if_rx doesn't parse nlmsg properly commit c88f0e6b06f4092995688211a631bb436125d77b upstream. 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 Signed-off-by: Xin Long Acked-by: Chris Leech Signed-off-by: Martin K. Petersen Signed-off-by: Greg Kroah-Hartman --- 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 42bca61..c39551b 100644 --- a/drivers/scsi/scsi_transport_iscsi.c +++ b/drivers/scsi/scsi_transport_iscsi.c @@ -3696,7 +3696,7 @@ 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; } -- 2.7.4