This is a note to let you know that I've just added the patch titled
tty: hvc: fix buffer overflow during hvc_alloc().
to my tty git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty.git
in the tty-linus branch.
The patch will show up in the next release of the linux-next tree
(usually sometime within the next 24 hours during the week.)
The patch will hopefully also be merged in Linus's tree for the
next -rc kernel release.
If you have any questions about this process, please let me know.
>From 9a9fc42b86c06120744555fea43fdcabe297c656 Mon Sep 17 00:00:00 2001
From: Andrew Melnychenko <andrew@xxxxxxxxxx>
Date: Tue, 14 Apr 2020 22:15:03 +0300
Subject: tty: hvc: fix buffer overflow during hvc_alloc().
If there is a lot(more then 16) of virtio-console devices
or virtio_console module is reloaded
- buffers 'vtermnos' and 'cons_ops' are overflowed.
In older kernels it overruns spinlock which leads to kernel freezing:
https://bugzilla.redhat.com/show_bug.cgi?id=1786239
To reproduce the issue, you can try simple script that
loads/unloads module. Something like this:
while [ 1 ]
do
modprobe virtio_console
sleep 2
modprobe -r virtio_console
sleep 2
done
Description of problem:
Guest get 'Call Trace' when loading module "virtio_console"
and unloading it frequently - clearly reproduced on kernel-4.18.0:
[ 81.498208] ------------[ cut here ]------------
[ 81.499263] pvqspinlock: lock 0xffffffff92080020 has corrupted value 0xc0774ca0!
[ 81.501000] WARNING: CPU: 0 PID: 785 at kernel/locking/qspinlock_paravirt.h:500 __pv_queued_spin_unlock_slowpath+0xc0/0xd0
[ 81.503173] Modules linked in: virtio_console fuse xt_CHECKSUM ipt_MASQUERADE xt_conntrack ipt_REJECT nft_counter nf_nat_tftp nft_objref nf_conntrack_tftp tun bridge stp llc nft_fib_inet nft_fib_ipv4 nft_fib_ipv6 nft_fib nft_reject_inet nf_reject_ipv4 nf_reject_ipv6 nft_reject nft_ct nf_tables_set nft_chain_nat_ipv6 nf_conntrack_ipv6 nf_defrag_ipv6 nf_nat_ipv6 nft_chain_route_ipv6 nft_chain_nat_ipv4 nf_conntrack_ipv4 nf_defrag_ipv4 nf_nat_ipv4 nf_nat nf_conntrack nft_chain_route_ipv4 ip6_tables nft_compat ip_set nf_tables nfnetlink sunrpc bochs_drm drm_vram_helper ttm drm_kms_helper syscopyarea sysfillrect sysimgblt fb_sys_fops drm i2c_piix4 pcspkr crct10dif_pclmul crc32_pclmul joydev ghash_clmulni_intel ip_tables xfs libcrc32c sd_mod sg ata_generic ata_piix virtio_net libata crc32c_intel net_failover failover serio_raw virtio_scsi dm_mirror dm_region_hash dm_log dm_mod [last unloaded: virtio_console]
[ 81.517019] CPU: 0 PID: 785 Comm: kworker/0:2 Kdump: loaded Not tainted 4.18.0-167.el8.x86_64 #1
[ 81.518639] Hardware name: Red Hat KVM, BIOS 1.12.0-5.scrmod+el8.2.0+5159+d8aa4d83 04/01/2014
[ 81.520205] Workqueue: events control_work_handler [virtio_console]
[ 81.521354] RIP: 0010:__pv_queued_spin_unlock_slowpath+0xc0/0xd0
[ 81.522450] Code: 07 00 48 63 7a 10 e8 bf 64 f5 ff 66 90 c3 8b 05 e6 cf d6 01 85 c0 74 01 c3 8b 17 48 89 fe 48 c7 c7 38 4b 29 91 e8 3a 6c fa ff <0f> 0b c3 0f 0b 90 90 90 90 90 90 90 90 90 90 90 0f 1f 44 00 00 48
[ 81.525830] RSP: 0018:ffffb51a01ffbd70 EFLAGS: 00010282
[ 81.526798] RAX: 0000000000000000 RBX: 0000000000000010 RCX: 0000000000000000
[ 81.528110] RDX: ffff9e66f1826480 RSI: ffff9e66f1816a08 RDI: ffff9e66f1816a08
[ 81.529437] RBP: ffffffff9153ff10 R08: 000000000000026c R09: 0000000000000053
[ 81.530732] R10: 0000000000000000 R11: ffffb51a01ffbc18 R12: ffff9e66cd682200
[ 81.532133] R13: ffffffff9153ff10 R14: ffff9e6685569500 R15: ffff9e66cd682000
[ 81.533442] FS: 0000000000000000(0000) GS:ffff9e66f1800000(0000) knlGS:0000000000000000
[ 81.534914] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 81.535971] CR2: 00005624c55b14d0 CR3: 00000003a023c000 CR4: 00000000003406f0
[ 81.537283] Call Trace:
[ 81.537763] __raw_callee_save___pv_queued_spin_unlock_slowpath+0x11/0x20
[ 81.539011] .slowpath+0x9/0xe
[ 81.539585] hvc_alloc+0x25e/0x300
[ 81.540237] init_port_console+0x28/0x100 [virtio_console]
[ 81.541251] handle_control_message.constprop.27+0x1c4/0x310 [virtio_console]
[ 81.542546] control_work_handler+0x70/0x10c [virtio_console]
[ 81.543601] process_one_work+0x1a7/0x3b0
[ 81.544356] worker_thread+0x30/0x390
[ 81.545025] ? create_worker+0x1a0/0x1a0
[ 81.545749] kthread+0x112/0x130
[ 81.546358] ? kthread_flush_work_fn+0x10/0x10
[ 81.547183] ret_from_fork+0x22/0x40
[ 81.547842] ---[ end trace aa97649bd16c8655 ]---
[ 83.546539] general protection fault: 0000 [#1] SMP NOPTI
[ 83.547422] CPU: 5 PID: 3225 Comm: modprobe Kdump: loaded Tainted: G W --------- - - 4.18.0-167.el8.x86_64 #1
[ 83.549191] Hardware name: Red Hat KVM, BIOS 1.12.0-5.scrmod+el8.2.0+5159+d8aa4d83 04/01/2014
[ 83.550544] RIP: 0010:__pv_queued_spin_lock_slowpath+0x19a/0x2a0
[ 83.551504] Code: c4 c1 ea 12 41 be 01 00 00 00 4c 8d 6d 14 41 83 e4 03 8d 42 ff 49 c1 e4 05 48 98 49 81 c4 40 a5 02 00 4c 03 24 c5 60 48 34 91 <49> 89 2c 24 b8 00 80 00 00 eb 15 84 c0 75 0a 41 0f b6 54 24 14 84
[ 83.554449] RSP: 0018:ffffb51a0323fdb0 EFLAGS: 00010202
[ 83.555290] RAX: 000000000000301c RBX: ffffffff92080020 RCX: 0000000000000001
[ 83.556426] RDX: 000000000000301d RSI: 0000000000000000 RDI: 0000000000000000
[ 83.557556] RBP: ffff9e66f196a540 R08: 000000000000028a R09: ffff9e66d2757788
[ 83.558688] R10: 0000000000000000 R11: 0000000000000000 R12: 646e61725f770b07
[ 83.559821] R13: ffff9e66f196a554 R14: 0000000000000001 R15: 0000000000180000
[ 83.560958] FS: 00007fd5032e8740(0000) GS:ffff9e66f1940000(0000) knlGS:0000000000000000
[ 83.562233] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 83.563149] CR2: 00007fd5022b0da0 CR3: 000000038c334000 CR4: 00000000003406e0
Signed-off-by: Andrew Melnychenko <andrew@xxxxxxxxxx>
Cc: stable <stable@xxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20200414191503.3471783-1-andrew@xxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/tty/hvc/hvc_console.c | 23 ++++++++++++++---------
1 file changed, 14 insertions(+), 9 deletions(-)
diff --git a/drivers/tty/hvc/hvc_console.c b/drivers/tty/hvc/hvc_console.c
index 27284a2dcd2b..436cc51c92c3 100644
--- a/drivers/tty/hvc/hvc_console.c
+++ b/drivers/tty/hvc/hvc_console.c
@@ -302,10 +302,6 @@ int hvc_instantiate(uint32_t vtermno, int index, const struct hv_ops *ops)
vtermnos[index] = vtermno;
cons_ops[index] = ops;
- /* reserve all indices up to and including this index */
- if (last_hvc < index)
- last_hvc = index;
-
/* check if we need to re-register the kernel console */
hvc_check_console(index);
@@ -960,13 +956,22 @@ struct hvc_struct *hvc_alloc(uint32_t vtermno, int data,
cons_ops[i] == hp->ops)
break;
- /* no matching slot, just use a counter */
- if (i >= MAX_NR_HVC_CONSOLES)
- i = ++last_hvc;
+ if (i >= MAX_NR_HVC_CONSOLES) {
+
+ /* find 'empty' slot for console */
+ for (i = 0; i < MAX_NR_HVC_CONSOLES && vtermnos[i] != -1; i++) {
+ }
+
+ /* no matching slot, just use a counter */
+ if (i == MAX_NR_HVC_CONSOLES)
+ i = ++last_hvc + MAX_NR_HVC_CONSOLES;
+ }
hp->index = i;
- cons_ops[i] = ops;
- vtermnos[i] = vtermno;
+ if (i < MAX_NR_HVC_CONSOLES) {
+ cons_ops[i] = ops;
+ vtermnos[i] = vtermno;
+ }
list_add_tail(&(hp->next), &hvc_structs);
mutex_unlock(&hvc_structs_mutex);
--
2.26.2
