Re: [UBSAN] iwlmvm's iwl_mvm_enable_txq accesses IEEE80211_INVAL_HW_QUEUE
On Fri, 2017-06-23 at 09:48 +0200, Jiri Slaby wrote: > > mac80211_queue is 255 which is IEEE80211_INVAL_HW_QUEUE, so it should > not be worked with at all. Funny you should find this today :-) > The invalid queue is hopefully handled in ieee80211_check_queues > after > drv_add_interface in ieee80211_do_open: > > res = drv_add_interface(local, sdata); > if (res) > goto err_stop; > res = ieee80211_check_queues(sdata, > ieee80211_vif_type_p2p(>vif)); > > > But the mvm driver still should not blindly shift 1 by 255 in > iwl_mvm_enable_txq. Should the check for the invalid queue be before > adding the interface in mac80211? Or should drivers check it in their > add_interface? Everything is actually handled well afaict, because the bug won't matter - this is a queue we'll never really stop, so we won't be looking at the (invalid) result of the calculation. I had actually been under the impression that it wasn't undefined but would just result in 0; that's clearly not true but also doesn't matter. AFAICT it even results in 0x8000 (which makes some sense, since 255 % 32 == 31), and that's a queue number (31) that's too big for mac80211 anyway, so it would warn if we were to ever try to stop it. In later versions of the code, however, there *was* indeed a bug - we were using a u8 instead of a u32 in the code we have internally. While fixing *that* bug, I also made this catch the case of IEEE80211_INVAL_HW_QUEUE so we'll not modify the bitmap at all, which is the correct thing to do. IOW - yes, it's not nice, but it also shouldn't matter, and even if for some strange reason we tried to stop the queue we'd just get a warning from mac80211. johannes
[UBSAN] iwlmvm's iwl_mvm_enable_txq accesses IEEE80211_INVAL_HW_QUEUE
Hi, we have got an UBSAN report from opensuse's user who booten UBSAN-enabled kernel by mistake: UBSAN: Undefined behaviour in drivers/net/wireless/intel/iwlwifi/mvm/utils.c:667:49 shift exponent 255 is too large for 64-bit type 'long unsigned int' CPU: 2 PID: 1590 Comm: wpa_supplicant Not tainted 4.11.2-1-syzkaller #1 Hardware name: Dell Inc. Precision 5510/0N8J4R, BIOS 01.02.00 04/07/2016 Call Trace: ... iwl_mvm_enable_txq+0xc6d/0x1080 [iwlmvm] iwl_mvm_send_add_bcast_sta+0x275/0x850 [iwlmvm] iwl_mvm_add_bcast_sta+0x11b/0x280 [iwlmvm] iwl_mvm_mac_add_interface+0x51f/0x8b0 [iwlmvm] drv_add_interface+0x1a7/0x8c0 [mac80211] ieee80211_do_open+0xdff/0x2790 [mac80211] ieee80211_start_p2p_device+0xac/0xf0 [mac80211] nl80211_start_p2p_device+0x25d/0xab0 [cfg80211] genl_family_rcv_msg+0x835/0xf10 genl_rcv_msg+0xd0/0x1c0 netlink_rcv_skb+0x226/0x310 genl_rcv+0x2d/0x40 netlink_unicast+0x631/0x9d0 netlink_sendmsg+0xa2e/0xf60 sock_sendmsg+0xf7/0x180 ___sys_sendmsg+0x777/0xa60 __sys_sendmsg+0xd6/0x170 SyS_sendmsg+0x32/0x50 entry_SYSCALL_64_fastpath+0x23/0xc6 mac80211_queue is 255 which is IEEE80211_INVAL_HW_QUEUE, so it should not be worked with at all. The invalid queue is hopefully handled in ieee80211_check_queues after drv_add_interface in ieee80211_do_open: res = drv_add_interface(local, sdata); if (res) goto err_stop; res = ieee80211_check_queues(sdata, ieee80211_vif_type_p2p(>vif)); But the mvm driver still should not blindly shift 1 by 255 in iwl_mvm_enable_txq. Should the check for the invalid queue be before adding the interface in mac80211? Or should drivers check it in their add_interface? thanks, -- js suse labs