[PATCH 3.2 040/185] loop: fix crash if blk_alloc_queue fails

Ben Hutchings
2013-12-29T02:08:43Z

From: Mikulas Patocka <mpatocka@redhat.com>

commit 3ec981e30fae1f3c8728a05c730acaa1f627bcfb upstream.

loop: fix crash if blk_alloc_queue fails

If blk_alloc_queue fails, loop_add cleans up, but it doesn't clean up the
identifier allocated with idr_alloc. That causes crash on module unload in
idr_for_each(&loop_index_idr, &loop_exit_cb, NULL); where we attempt to
remove non-existed device with that id.

BUG: unable to handle kernel NULL pointer dereference at 0000000000000380
IP: [<ffffffff812057c9>] del_gendisk+0x19/0x2d0
PGD 43d399067 PUD 43d0ad067 PMD 0
Oops: 0000 [#1] PREEMPT SMP
Modules linked in: loop(-) dm_snapshot dm_zero dm_mirror dm_region_hash dm_log dm_loop dm_mod ip6table_filter ip6_tables uvesafb cfbcopyarea cfbimgblt cfbfillrect fbcon font bitblit fbcon_rotate fbcon_cw fbcon_ud fbcon_ccw softcursor fb fbdev msr ipt_MASQUERADE iptable_nat nf_nat_ipv4 nf_conntrack_ipv4 nf_defrag_ipv4 xt_state ipt_REJECT xt_tcpudp iptable_filter ip_tables x_tables bridge stp llc tun ipv6 cpufreq_userspace cpufreq_stats cpufreq_ondemand cpufreq_conservative cpufreq_powersave spadfs fuse hid_generic usbhid hid raid0 md_mod dmi_sysfs nf_nat_ftp nf_nat nf_conntrack_ftp nf_conntrack snd_usb_audio snd_pcm_oss snd_mixer_oss snd_pcm snd_timer snd_page_alloc lm85 hwmon_vid snd_hwdep snd_usbmidi_lib snd_rawmidi snd soundcore acpi_cpufreq ohci_hcd freq_table tg3 ehci_pci mperf ehci_hcd kvm_amd kvm sata_svw serverworks libphy libata ide_core k10temp usbcore hwmon microcode ptp pcspkr pps_core e100 skge mii usb_common i2c_piix4 floppy evdev rtc_cmos i2c_core processor but!
ton unix
CPU: 7 PID: 2735 Comm: rmmod Tainted: G W 3.10.15-devel #15
Hardware name: empty empty/S3992-E, BIOS 'V1.06 ' 06/09/2009
task: ffff88043d38e780 ti: ffff88043d21e000 task.ti: ffff88043d21e000
RIP: 0010:[<ffffffff812057c9>] [<ffffffff812057c9>] del_gendisk+0x19/0x2d0
RSP: 0018:ffff88043d21fe10 EFLAGS: 00010282
RAX: ffffffffa05102e0 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffff88043ea82800 RDI: 0000000000000000
RBP: ffff88043d21fe48 R08: 0000000000000000 R09: 0000000000000001
R10: 0000000000000001 R11: 0000000000000000 R12: 00000000000000ff
R13: 0000000000000080 R14: 0000000000000000 R15: ffff88043ea82800
FS: 00007ff646534700(0000) GS:ffff880447000000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
CR2: 0000000000000380 CR3: 000000043e9bf000 CR4: 00000000000007e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Stack:
ffffffff8100aba4 0000000000000092 ffff88043d21fe48 ffff88043ea82800
00000000000000ff ffff88043d21fe98 0000000000000000 ffff88043d21fe60
ffffffffa05102b4 0000000000000000 ffff88043d21fe70 ffffffffa05102ec
Call Trace:
[<ffffffff8100aba4>] ? native_sched_clock+0x24/0x80
[<ffffffffa05102b4>] loop_remove+0x14/0x40 [loop]
[<ffffffffa05102ec>] loop_exit_cb+0xc/0x10 [loop]
[<ffffffff81217b74>] idr_for_each+0x104/0x190
[<ffffffffa05102e0>] ? loop_remove+0x40/0x40 [loop]
[<ffffffff8109adc5>] ? trace_hardirqs_on_caller+0x105/0x1d0
[<ffffffffa05135dc>] loop_exit+0x34/0xa58 [loop]
[<ffffffff810a98ea>] SyS_delete_module+0x13a/0x260
[<ffffffff81221d5e>] ? trace_hardirqs_on_thunk+0x3a/0x3f
[<ffffffff813cff16>] system_call_fastpath+0x1a/0x1f
Code: f0 4c 8b 6d f8 c9 c3 66 66 2e 0f 1f 84 00 00 00 00 00 55 48 89 e5 41 56 41 55 4c 8d af 80 00 00 00 41 54 53 48 89 fb 48 83 ec 18 <48> 83 bf 80 03 00
00 00 74 4d e8 98 fe ff ff 31 f6 48 c7 c7 20
RIP [<ffffffff812057c9>] del_gendisk+0x19/0x2d0
RSP <ffff88043d21fe10>
CR2: 0000000000000380
---[ end trace 64ec069ec70f1309 ]---

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
drivers/block/loop.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -1635,7 +1635,7 @@ static int loop_add(struct loop_device *

lo->lo_queue = blk_alloc_queue(GFP_KERNEL);
if (!lo->lo_queue)
- goto out_free_dev;
+ goto out_free_idr;

disk = lo->lo_disk = alloc_disk(1 << part_shift);
if (!disk)
@@ -1679,6 +1679,8 @@ static int loop_add(struct loop_device *

out_free_queue:
blk_cleanup_queue(lo->lo_queue);
+out_free_idr:
+ idr_remove(&loop_index_idr, i);
out_free_dev:
kfree(lo);