[PATCH 4.19 006/118] block: brd: associate with queue until adding disk

Greg Kroah-Hartman
2018-11-26T11:03:08Z

[ Upstream commit 153fcd5f6d93b8e1e4040b1337f564a10f8d93af ]

brd_free() may be called in failure path on one brd instance which
disk isn't added yet, so release handler of gendisk may free the
associated request_queue early and causes the following use-after-free[1].

This patch fixes this issue by associating gendisk with request_queue
just before adding disk.

[1] KASAN: use-after-free Read in del_timer_syncNon-volatile memory driver v1.3
Linux agpgart interface v0.103
[drm] Initialized vgem 1.0.0 20120112 for virtual device on minor 0
usbcore: registered new interface driver udl
==================================================================
BUG: KASAN: use-after-free in __lock_acquire+0x36d9/0x4c20
kernel/locking/lockdep.c:3218
Read of size 8 at addr ffff8801d1b6b540 by task swapper/0/1

CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.19.0+ #88
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x244/0x39d lib/dump_stack.c:113
print_address_description.cold.7+0x9/0x1ff mm/kasan/report.c:256
kasan_report_error mm/kasan/report.c:354 [inline]
kasan_report.cold.8+0x242/0x309 mm/kasan/report.c:412
__asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
__lock_acquire+0x36d9/0x4c20 kernel/locking/lockdep.c:3218
lock_acquire+0x1ed/0x520 kernel/locking/lockdep.c:3844
del_timer_sync+0xb7/0x270 kernel/time/timer.c:1283
blk_cleanup_queue+0x413/0x710 block/blk-core.c:809
brd_free+0x5d/0x71 drivers/block/brd.c:422
brd_init+0x2eb/0x393 drivers/block/brd.c:518
do_one_initcall+0x145/0x957 init/main.c:890
do_initcall_level init/main.c:958 [inline]
do_initcalls init/main.c:966 [inline]
do_basic_setup init/main.c:984 [inline]
kernel_init_freeable+0x5c6/0x6b9 init/main.c:1148
kernel_init+0x11/0x1ae init/main.c:1068
ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:350

Reported-by: syzbot+3701447012fe951dabb2@syzkaller.appspotmail.com
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/block/brd.c | 16 +++++++++++-----
1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/drivers/block/brd.c b/drivers/block/brd.c
index df8103dd40ac..c18586fccb6f 100644
--- a/drivers/block/brd.c
+++ b/drivers/block/brd.c
@@ -396,15 +396,14 @@ static struct brd_device *brd_alloc(int i)
disk->first_minor = i * max_part;
disk->fops = &brd_fops;
disk->private_data = brd;
- disk->queue = brd->brd_queue;
disk->flags = GENHD_FL_EXT_DEVT;
sprintf(disk->disk_name, "ram%d", i);
set_capacity(disk, rd_size * 2);
- disk->queue->backing_dev_info->capabilities |= BDI_CAP_SYNCHRONOUS_IO;
+ brd->brd_queue->backing_dev_info->capabilities |= BDI_CAP_SYNCHRONOUS_IO;

/* Tell the block layer that this is not a rotational device */
- blk_queue_flag_set(QUEUE_FLAG_NONROT, disk->queue);
- blk_queue_flag_clear(QUEUE_FLAG_ADD_RANDOM, disk->queue);
+ blk_queue_flag_set(QUEUE_FLAG_NONROT, brd->brd_queue);
+ blk_queue_flag_clear(QUEUE_FLAG_ADD_RANDOM, brd->brd_queue);

return brd;

@@ -436,6 +435,7 @@ static struct brd_device *brd_init_one(int i, bool *new)

brd = brd_alloc(i);
if (brd) {
+ brd->brd_disk->queue = brd->brd_queue;
add_disk(brd->brd_disk);
list_add_tail(&brd->brd_list, &brd_devices);
}
@@ -503,8 +503,14 @@ static int __init brd_init(void)

/* point of no return */

- list_for_each_entry(brd, &brd_devices, brd_list)
+ list_for_each_entry(brd, &brd_devices, brd_list) {
+ /*
+ * associate with queue just before adding disk for
+ * avoiding to mess up failure path
+ */
+ brd->brd_disk->queue = brd->brd_queue;
add_disk(brd->brd_disk);
+ }

blk_register_region(MKDEV(RAMDISK_MAJOR, 0), 1UL << MINORBITS,
THIS_MODULE, brd_probe, NULL, NULL);
--
2.17.1