[PATCH AUTOSEL 5.8 17/72] blktrace: fix debugfs use after free

[PATCH AUTOSEL 5.8 17/72] blktrace: fix debugfs use after free

[Sasha Levin]

From: Luis Chamberlain <mcgrof@kernel.org>

[ Upstream commit bad8e64fb19d3a0de5e564d9a7271c31bd684369 ]

On commit 6ac93117ab00 ("blktrace: use existing disk debugfs directory")
merged on v4.12 Omar fixed the original blktrace code for request-based
drivers (multiqueue). This however left in place a possible crash, if you
happen to abuse blktrace while racing to remove / add a device.

We used to use asynchronous removal of the request_queue, and with that
the issue was easier to reproduce. Now that we have reverted to
synchronous removal of the request_queue, the issue is still possible to
reproduce, its however just a bit more difficult.

We essentially run two instances of break-blktrace which add/remove
a loop device, and setup a blktrace and just never tear the blktrace
down. We do this twice in parallel. This is easily reproduced with the
script run_0004.sh from break-blktrace [0].

We can end up with two types of panics each reflecting where we
race, one a failed blktrace setup:

[  252.426751] debugfs: Directory 'loop0' with parent 'block' already present!
[  252.432265] BUG: kernel NULL pointer dereference, address: 00000000000000a0
[  252.436592] #PF: supervisor write access in kernel mode
[  252.439822] #PF: error_code(0x0002) - not-present page
[  252.442967] PGD 0 P4D 0
[  252.444656] Oops: 0002 [#1] SMP NOPTI
[  252.446972] CPU: 10 PID: 1153 Comm: break-blktrace Tainted: G            E     5.7.0-rc2-next-20200420+ #164
[  252.452673] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1 04/01/2014
[  252.456343] RIP: 0010:down_write+0x15/0x40
[  252.458146] Code: eb ca e8 ae 22 8d ff cc cc cc cc cc cc cc cc cc cc cc cc
               cc cc 0f 1f 44 00 00 55 48 89 fd e8 52 db ff ff 31 c0 ba 01 00
               00 00 <f0> 48 0f b1 55 00 75 0f 48 8b 04 25 c0 8b 01 00 48 89
               45 08 5d
[  252.463638] RSP: 0018:ffffa626415abcc8 EFLAGS: 00010246
[  252.464950] RAX: 0000000000000000 RBX: ffff958c25f0f5c0 RCX: ffffff8100000000
[  252.466727] RDX: 0000000000000001 RSI: ffffff8100000000 RDI: 00000000000000a0
[  252.468482] RBP: 00000000000000a0 R08: 0000000000000000 R09: 0000000000000001
[  252.470014] R10: 0000000000000000 R11: ffff958d1f9227ff R12: 0000000000000000
[  252.471473] R13: ffff958c25ea5380 R14: ffffffff8cce15f1 R15: 00000000000000a0
[  252.473346] FS:  00007f2e69dee540(0000) GS:ffff958c2fc80000(0000) knlGS:0000000000000000
[  252.475225] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  252.476267] CR2: 00000000000000a0 CR3: 0000000427d10004 CR4: 0000000000360ee0
[  252.477526] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[  252.478776] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[  252.479866] Call Trace:
[  252.480322]  simple_recursive_removal+0x4e/0x2e0
[  252.481078]  ? debugfs_remove+0x60/0x60
[  252.481725]  ? relay_destroy_buf+0x77/0xb0
[  252.482662]  debugfs_remove+0x40/0x60
[  252.483518]  blk_remove_buf_file_callback+0x5/0x10
[  252.484328]  relay_close_buf+0x2e/0x60
[  252.484930]  relay_open+0x1ce/0x2c0
[  252.485520]  do_blk_trace_setup+0x14f/0x2b0
[  252.486187]  __blk_trace_setup+0x54/0xb0
[  252.486803]  blk_trace_ioctl+0x90/0x140
[  252.487423]  ? do_sys_openat2+0x1ab/0x2d0
[  252.488053]  blkdev_ioctl+0x4d/0x260
[  252.488636]  block_ioctl+0x39/0x40
[  252.489139]  ksys_ioctl+0x87/0xc0
[  252.489675]  __x64_sys_ioctl+0x16/0x20
[  252.490380]  do_syscall_64+0x52/0x180
[  252.491032]  entry_SYSCALL_64_after_hwframe+0x44/0xa9

And the other on the device removal:

[  128.528940] debugfs: Directory 'loop0' with parent 'block' already present!
[  128.615325] BUG: kernel NULL pointer dereference, address: 00000000000000a0
[  128.619537] #PF: supervisor write access in kernel mode
[  128.622700] #PF: error_code(0x0002) - not-present page
[  128.625842] PGD 0 P4D 0
[  128.627585] Oops: 0002 [#1] SMP NOPTI
[  128.629871] CPU: 12 PID: 544 Comm: break-blktrace Tainted: G            E     5.7.0-rc2-next-20200420+ #164
[  128.635595] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1 04/01/2014
[  128.640471] RIP: 0010:down_write+0x15/0x40
[  128.643041] Code: eb ca e8 ae 22 8d ff cc cc cc cc cc cc cc cc cc cc cc cc
               cc cc 0f 1f 44 00 00 55 48 89 fd e8 52 db ff ff 31 c0 ba 01 00
               00 00 <f0> 48 0f b1 55 00 75 0f 65 48 8b 04 25 c0 8b 01 00 48 89
               45 08 5d
[  128.650180] RSP: 0018:ffffa9c3c05ebd78 EFLAGS: 00010246
[  128.651820] RAX: 0000000000000000 RBX: ffff8ae9a6370240 RCX: ffffff8100000000
[  128.653942] RDX: 0000000000000001 RSI: ffffff8100000000 RDI: 00000000000000a0
[  128.655720] RBP: 00000000000000a0 R08: 0000000000000002 R09: ffff8ae9afd2d3d0
[  128.657400] R10: 0000000000000056 R11: 0000000000000000 R12: 0000000000000000
[  128.659099] R13: 0000000000000000 R14: 0000000000000003 R15: 00000000000000a0
[  128.660500] FS:  00007febfd995540(0000) GS:ffff8ae9afd00000(0000) knlGS:0000000000000000
[  128.662204] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  128.663426] CR2: 00000000000000a0 CR3: 0000000420042003 CR4: 0000000000360ee0
[  128.664776] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[  128.666022] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[  128.667282] Call Trace:
[  128.667801]  simple_recursive_removal+0x4e/0x2e0
[  128.668663]  ? debugfs_remove+0x60/0x60
[  128.669368]  debugfs_remove+0x40/0x60
[  128.669985]  blk_trace_free+0xd/0x50
[  128.670593]  __blk_trace_remove+0x27/0x40
[  128.671274]  blk_trace_shutdown+0x30/0x40
[  128.671935]  blk_release_queue+0x95/0xf0
[  128.672589]  kobject_put+0xa5/0x1b0
[  128.673188]  disk_release+0xa2/0xc0
[  128.673786]  device_release+0x28/0x80
[  128.674376]  kobject_put+0xa5/0x1b0
[  128.674915]  loop_remove+0x39/0x50 [loop]
[  128.675511]  loop_control_ioctl+0x113/0x130 [loop]
[  128.676199]  ksys_ioctl+0x87/0xc0
[  128.676708]  __x64_sys_ioctl+0x16/0x20
[  128.677274]  do_syscall_64+0x52/0x180
[  128.677823]  entry_SYSCALL_64_after_hwframe+0x44/0xa9

The common theme here is:

debugfs: Directory 'loop0' with parent 'block' already present

This crash happens because of how blktrace uses the debugfs directory
where it places its files. Upon init we always create the same directory
which would be needed by blktrace but we only do this for make_request
drivers (multiqueue) block drivers. When you race a removal of these
devices with a blktrace setup you end up in a situation where the
make_request recursive debugfs removal will sweep away the blktrace
files and then later blktrace will also try to remove individual
dentries which are already NULL. The inverse is also possible and hence
the two types of use after frees.

We don't create the block debugfs directory on init for these types of
block devices:

  * request-based block driver block devices
  * every possible partition
  * scsi-generic

And so, this race should in theory only be possible with make_request
drivers.

We can fix the UAF by simply re-using the debugfs directory for
make_request drivers (multiqueue) and only creating the ephemeral
directory for the other type of block devices. The new clarifications
on relying on the q->blk_trace_mutex *and* also checking for q->blk_trace
*prior* to processing a blktrace ensures the debugfs directories are
only created if no possible directory name clashes are possible.

This goes tested with:

  o nvme partitions
  o ISCSI with tgt, and blktracing against scsi-generic with:
    o block
    o tape
    o cdrom
    o media changer
  o blktests

This patch is part of the work which disputes the severity of
CVE-2019-19770 which shows this issue is not a core debugfs issue, but
a misuse of debugfs within blktace.

Fixes: 6ac93117ab00 ("blktrace: use existing disk debugfs directory")
Reported-by: syzbot+603294af2d01acfdd6da@syzkaller.appspotmail.com
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Bart Van Assche <bvanassche@acm.org>
Cc: Omar Sandoval <osandov@fb.com>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Nicolai Stange <nstange@suse.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: "Martin K. Petersen" <martin.petersen@oracle.com>
Cc: "James E.J. Bottomley" <jejb@linux.ibm.com>
Cc: yu kuai <yukuai3@huawei.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 kernel/trace/blktrace.c | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c
index 5ef0484513ecb..588e8e3960197 100644
--- a/kernel/trace/blktrace.c
+++ b/kernel/trace/blktrace.c
@@ -522,10 +522,18 @@ static int do_blk_trace_setup(struct request_queue *q, char *name, dev_t dev,
 	if (!bt->msg_data)
 		goto err;
 
-	ret = -ENOENT;
-
-	dir = debugfs_lookup(buts->name, blk_debugfs_root);
-	if (!dir)
+#ifdef CONFIG_BLK_DEBUG_FS
+	/*
+	 * When tracing whole make_request drivers (multiqueue) block devices,
+	 * reuse the existing debugfs directory created by the block layer on
+	 * init. For request-based block devices, all partitions block devices,
+	 * and scsi-generic block devices we create a temporary new debugfs
+	 * directory that will be removed once the trace ends.
+	 */
+	if (queue_is_mq(q) && bdev && bdev == bdev->bd_contains)
+		dir = q->debugfs_dir;
+	else
+#endif
 		bt->dir = dir = debugfs_create_dir(buts->name, blk_debugfs_root);
 
 	bt->dev = dev;
@@ -563,8 +571,6 @@ static int do_blk_trace_setup(struct request_queue *q, char *name, dev_t dev,
 
 	ret = 0;
 err:
-	if (dir && !bt->dir)
-		dput(dir);
 	if (ret)
 		blk_trace_free(bt);
 	return ret;
-- 
2.25.1

[PATCH AUTOSEL 5.8 54/72] iocost: Fix check condition of iocg abs_vdebt

[Sasha Levin]

From: Chengming Zhou <zhouchengming@bytedance.com>

[ Upstream commit d9012a59db54442d5b2fcfdfcded35cf566397d3 ]

We shouldn't skip iocg when its abs_vdebt is not zero.

Fixes: 0b80f9866e6b ("iocost: protect iocg->abs_vdebt with iocg->waitq.lock")
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 block/blk-iocost.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/block/blk-iocost.c b/block/blk-iocost.c
index 8ac4aad66ebc3..86ba6fd254e1d 100644
--- a/block/blk-iocost.c
+++ b/block/blk-iocost.c
@@ -1370,7 +1370,7 @@ static void ioc_timer_fn(struct timer_list *timer)
 	 * should have woken up in the last period and expire idle iocgs.
 	 */
 	list_for_each_entry_safe(iocg, tiocg, &ioc->active_iocgs, active_list) {
-		if (!waitqueue_active(&iocg->waitq) && iocg->abs_vdebt &&
+		if (!waitqueue_active(&iocg->waitq) && !iocg->abs_vdebt &&
 		    !iocg_is_idle(iocg))
 			continue;
 
-- 
2.25.1

[PATCH AUTOSEL 5.8 72/72] block: don't do revalidate zones on invalid devices

[Sasha Levin]

From: Johannes Thumshirn <johannes.thumshirn@wdc.com>

[ Upstream commit 1a1206dc4cf02cee4b5cbce583ee4c22368b4c28 ]

When we loose a device for whatever reason while (re)scanning zones, we
trip over a NULL pointer in blk_revalidate_zone_cb, like in the following
log:

sd 0:0:0:0: [sda] 3418095616 4096-byte logical blocks: (14.0 TB/12.7 TiB)
sd 0:0:0:0: [sda] 52156 zones of 65536 logical blocks
sd 0:0:0:0: [sda] Write Protect is off
sd 0:0:0:0: [sda] Mode Sense: 37 00 00 08
sd 0:0:0:0: [sda] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA
sd 0:0:0:0: [sda] REPORT ZONES start lba 1065287680 failed
sd 0:0:0:0: [sda] REPORT ZONES: Result: hostbyte=0x00 driverbyte=0x08
sd 0:0:0:0: [sda] Sense Key : 0xb [current]
sd 0:0:0:0: [sda] ASC=0x0 ASCQ=0x6
sda: failed to revalidate zones
sd 0:0:0:0: [sda] 0 4096-byte logical blocks: (0 B/0 B)
sda: detected capacity change from 14000519643136 to 0
==================================================================
BUG: KASAN: null-ptr-deref in blk_revalidate_zone_cb+0x1b7/0x550
Write of size 8 at addr 0000000000000010 by task kworker/u4:1/58

CPU: 1 PID: 58 Comm: kworker/u4:1 Not tainted 5.8.0-rc1 #692
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4-rebuilt.opensuse.org 04/01/2014
Workqueue: events_unbound async_run_entry_fn
Call Trace:
 dump_stack+0x7d/0xb0
 ? blk_revalidate_zone_cb+0x1b7/0x550
 kasan_report.cold+0x5/0x37
 ? blk_revalidate_zone_cb+0x1b7/0x550
 check_memory_region+0x145/0x1a0
 blk_revalidate_zone_cb+0x1b7/0x550
 sd_zbc_parse_report+0x1f1/0x370
 ? blk_req_zone_write_trylock+0x200/0x200
 ? sectors_to_logical+0x60/0x60
 ? blk_req_zone_write_trylock+0x200/0x200
 ? blk_req_zone_write_trylock+0x200/0x200
 sd_zbc_report_zones+0x3c4/0x5e0
 ? sd_dif_config_host+0x500/0x500
 blk_revalidate_disk_zones+0x231/0x44d
 ? _raw_write_lock_irqsave+0xb0/0xb0
 ? blk_queue_free_zone_bitmaps+0xd0/0xd0
 sd_zbc_read_zones+0x8cf/0x11a0
 sd_revalidate_disk+0x305c/0x64e0
 ? __device_add_disk+0x776/0xf20
 ? read_capacity_16.part.0+0x1080/0x1080
 ? blk_alloc_devt+0x250/0x250
 ? create_object.isra.0+0x595/0xa20
 ? kasan_unpoison_shadow+0x33/0x40
 sd_probe+0x8dc/0xcd2
 really_probe+0x20e/0xaf0
 __driver_attach_async_helper+0x249/0x2d0
 async_run_entry_fn+0xbe/0x560
 process_one_work+0x764/0x1290
 ? _raw_read_unlock_irqrestore+0x30/0x30
 worker_thread+0x598/0x12f0
 ? __kthread_parkme+0xc6/0x1b0
 ? schedule+0xed/0x2c0
 ? process_one_work+0x1290/0x1290
 kthread+0x36b/0x440
 ? kthread_create_worker_on_cpu+0xa0/0xa0
 ret_from_fork+0x22/0x30
==================================================================

When the device is already gone we end up with the following scenario:
The device's capacity is 0 and thus the number of zones will be 0 as well. When
allocating the bitmap for the conventional zones, we then trip over a NULL
pointer.

So if we encounter a zoned block device with a 0 capacity, don't dare to
revalidate the zones sizes.

Fixes: 6c6b35491422 ("block: set the zone size in blk_revalidate_disk_zones atomically")
Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 block/blk-zoned.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/block/blk-zoned.c b/block/blk-zoned.c
index 23831fa8701d8..480dfff69a00c 100644
--- a/block/blk-zoned.c
+++ b/block/blk-zoned.c
@@ -497,6 +497,9 @@ int blk_revalidate_disk_zones(struct gendisk *disk,
 	if (WARN_ON_ONCE(!queue_is_mq(q)))
 		return -EIO;
 
+	if (!get_capacity(disk))
+		return -EIO;
+
 	/*
 	 * Ensure that all memory allocations in this context are done as if
 	 * GFP_NOIO was specified.
-- 
2.25.1