[PATCH 1/2] ubi: fix slab-out-of-bounds in ubi_eba_get_ldesc+0xfb/0x130

From: ZhaoLong Wang
Date: Thu Apr 06 2023 - 03:13:51 EST

From: Guo Xuenan <guoxuenan@xxxxxxxxxx>

When using ioctl interface to resize ubi volume, ubi_resize_volume will
resize eba table first, but not change vol->reserved_pebs in the same
atomic context which may cause concurrency access eba table.

For example, When user do shrink ubi volume A calling ubi_resize_volume,
while the other thread is writing (volume B) and triggering wear-leveling,
which may calling ubi_write_fastmap, under these circumstances, KASAN may
report: slab-out-of-bounds in ubi_eba_get_ldesc+0xfb/0x130.

The main work of this patch include:
1. fix races in ubi_resize_volume and ubi_update_fastmap, to avoid
eba_tbl read out of bounds. first, we make eba_tbl and reserved_pebs
updating under the protect of vol->volumes_lock. second, rollback
volume in case of resize failure. Also mention that for volume
shrinking failure, since part of volume has been shrunk and unmapped,
there is no need to recover {rsvd/avail}_pebs.
2. fix some memleak in error path of ubi_resize_volume when destroy
new_eba_tbl.

==================================================================
BUG: KASAN: slab-out-of-bounds in ubi_eba_get_ldesc+0xfb/0x130 [ubi]
Read of size 4 at addr ffff88800f43f570 by task kworker/u16:0/7
CPU: 0 PID: 7 Comm: kworker/u16:0 Not tainted 5.16.0-rc7 #3
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014
Workqueue: writeback wb_workfn (flush-ubifs_0_0)
Call Trace:
<TASK>
dump_stack_lvl+0x4d/0x66
print_address_description.constprop.0+0x41/0x60
kasan_report.cold+0x83/0xdf
ubi_eba_get_ldesc+0xfb/0x130 [ubi]
ubi_update_fastmap.cold+0x60f/0xc7d [ubi]
ubi_wl_get_peb+0x25b/0x4f0 [ubi]
try_write_vid_and_data+0x9a/0x4d0 [ubi]
ubi_eba_write_leb+0x7e4/0x17d0 [ubi]
ubi_leb_map+0x1a0/0x2c0 [ubi]
ubifs_leb_map+0x139/0x270 [ubifs]
ubifs_add_bud_to_log+0xb40/0xf30 [ubifs]
make_reservation+0x86e/0xb00 [ubifs]
ubifs_jnl_write_data+0x430/0x9d0 [ubifs]
do_writepage+0x1d1/0x550 [ubifs]
ubifs_writepage+0x37c/0x670 [ubifs]
__writepage+0x67/0x170
write_cache_pages+0x259/0xa90
do_writepages+0x277/0x5d0
__writeback_single_inode+0xb8/0x850
writeback_sb_inodes+0x4b3/0xb20
__writeback_inodes_wb+0xc1/0x220
wb_writeback+0x59f/0x740
wb_workfn+0x6d0/0xca0
process_one_work+0x711/0xfc0
worker_thread+0x95/0xd00
kthread+0x3a6/0x490
ret_from_fork+0x1f/0x30
</TASK>

Allocated by task 711:
kasan_save_stack+0x1e/0x50
__kasan_kmalloc+0x81/0xa0
ubi_eba_create_table+0x88/0x1a0 [ubi]
ubi_resize_volume.cold+0x175/0xae7 [ubi]
ubi_cdev_ioctl+0x57f/0x1a60 [ubi]
__x64_sys_ioctl+0x13a/0x1c0
do_syscall_64+0x35/0x80
entry_SYSCALL_64_after_hwframe+0x44/0xae

Last potentially related work creation:
kasan_save_stack+0x1e/0x50
__kasan_record_aux_stack+0xb7/0xc0
call_rcu+0xd6/0x1000
blk_stat_free_callback+0x28/0x30
blk_release_queue+0x8a/0x2e0
kobject_put+0x186/0x4c0
scsi_device_dev_release_usercontext+0x620/0xbd0
execute_in_process_context+0x2f/0x120
device_release+0xa4/0x240
kobject_put+0x186/0x4c0
put_device+0x20/0x30
__scsi_remove_device+0x1c3/0x300
scsi_probe_and_add_lun+0x2140/0x2eb0
__scsi_scan_target+0x1f2/0xbb0
scsi_scan_channel+0x11b/0x1a0
scsi_scan_host_selected+0x24c/0x310
do_scsi_scan_host+0x1e0/0x250
do_scan_async+0x45/0x490
async_run_entry_fn+0xa2/0x530
process_one_work+0x711/0xfc0
worker_thread+0x95/0xd00
kthread+0x3a6/0x490
ret_from_fork+0x1f/0x30
The buggy address belongs to the object at ffff88800f43f500
which belongs to the cache kmalloc-128 of size 128
The buggy address is located 112 bytes inside of
128-byte region [ffff88800f43f500, ffff88800f43f580)
The buggy address belongs to the page:
page:ffffea00003d0f00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0xf43c
head:ffffea00003d0f00 order:2 compound_mapcount:0 compound_pincount:0
flags: 0x1fffff80010200(slab|head|node=0|zone=1|lastcpupid=0x1fffff)
raw: 001fffff80010200 ffffea000046ba08 ffffea0000457208 ffff88810004d1c0
raw: 0000000000000000 0000000000190019 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
Memory state around the buggy address:
ffff88800f43f400: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88800f43f480: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88800f43f500: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 fc fc
^
ffff88800f43f580: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88800f43f600: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc

The following steps can used to reproduce:
Process 1: write and trigger ubi wear-leveling
ubimkvol /dev/ubi0 -s 5000MiB -N v1
ubimkvol /dev/ubi0 -s 2000MiB -N v2
ubimkvol /dev/ubi0 -s 10MiB -N v3
mount -t ubifs /dev/ubi0_0 /mnt/ubifs
while true;
do
filename=/mnt/ubifs/$((RANDOM))
dd if=/dev/random of=${filename} bs=1M count=$((RANDOM % 1000))
rm -rf ${filename}
sync /mnt/ubifs/
done

Process 2: do random resize
struct ubi_rsvol_req req;
req.vol_id = 1;
req.bytes = (rand() % 50) * 512KB;
ioctl(fd, UBI_IOCRSVOL, &req);

Signed-off-by: Guo Xuenan <guoxuenan@xxxxxxxxxx>
Signed-off-by: ZhaoLong Wang <wangzhaolong1@xxxxxxxxxx>
---
drivers/mtd/ubi/vmt.c | 24 +++++++++++++++++-------
1 file changed, 17 insertions(+), 7 deletions(-)

diff --git a/drivers/mtd/ubi/vmt.c b/drivers/mtd/ubi/vmt.c
index 2c867d16f89f..97294def01eb 100644
--- a/drivers/mtd/ubi/vmt.c
+++ b/drivers/mtd/ubi/vmt.c
@@ -408,6 +408,7 @@ int ubi_resize_volume(struct ubi_volume_desc *desc, int reserved_pebs)
struct ubi_device *ubi = vol->ubi;
struct ubi_vtbl_record vtbl_rec;
struct ubi_eba_table *new_eba_tbl = NULL;
+ struct ubi_eba_table *old_eba_tbl = NULL;
int vol_id = vol->vol_id;

if (ubi->ro_mode)
@@ -453,10 +454,13 @@ int ubi_resize_volume(struct ubi_volume_desc *desc, int reserved_pebs)
err = -ENOSPC;
goto out_free;
}
+
ubi->avail_pebs -= pebs;
ubi->rsvd_pebs += pebs;
ubi_eba_copy_table(vol, new_eba_tbl, vol->reserved_pebs);
- ubi_eba_replace_table(vol, new_eba_tbl);
+ old_eba_tbl = vol->eba_tbl;
+ vol->eba_tbl = new_eba_tbl;
+ vol->reserved_pebs = reserved_pebs;
spin_unlock(&ubi->volumes_lock);
}

@@ -471,7 +475,9 @@ int ubi_resize_volume(struct ubi_volume_desc *desc, int reserved_pebs)
ubi->avail_pebs -= pebs;
ubi_update_reserved(ubi);
ubi_eba_copy_table(vol, new_eba_tbl, reserved_pebs);
- ubi_eba_replace_table(vol, new_eba_tbl);
+ old_eba_tbl = vol->eba_tbl;
+ vol->eba_tbl = new_eba_tbl;
+ vol->reserved_pebs = reserved_pebs;
spin_unlock(&ubi->volumes_lock);
}

@@ -493,7 +499,6 @@ int ubi_resize_volume(struct ubi_volume_desc *desc, int reserved_pebs)
if (err)
goto out_acc;

- vol->reserved_pebs = reserved_pebs;
if (vol->vol_type == UBI_DYNAMIC_VOLUME) {
vol->used_ebs = reserved_pebs;
vol->last_eb_bytes = vol->usable_leb_size;
@@ -501,19 +506,24 @@ int ubi_resize_volume(struct ubi_volume_desc *desc, int reserved_pebs)
(long long)vol->used_ebs * vol->usable_leb_size;
}

+ /* destroy old table */
+ ubi_eba_destroy_table(old_eba_tbl);
ubi_volume_notify(ubi, vol, UBI_VOLUME_RESIZED);
self_check_volumes(ubi);
return err;

out_acc:
+ spin_lock(&ubi->volumes_lock);
+ vol->reserved_pebs = reserved_pebs - pebs;
if (pebs > 0) {
- spin_lock(&ubi->volumes_lock);
ubi->rsvd_pebs -= pebs;
ubi->avail_pebs += pebs;
- spin_unlock(&ubi->volumes_lock);
+ ubi_eba_copy_table(vol, old_eba_tbl, vol->reserved_pebs);
+ } else {
+ ubi_eba_copy_table(vol, old_eba_tbl, reserved_pebs);
}
- return err;
-
+ vol->eba_tbl = old_eba_tbl;
+ spin_unlock(&ubi->volumes_lock);
out_free:
ubi_eba_destroy_table(new_eba_tbl);
return err;
--
2.31.1