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Date: Thu, 6 Apr 2023 19:45:38 +0800
From: Zhihao Cheng <chengzhihao1@...wei.com>
To: ZhaoLong Wang <wangzhaolong1@...wei.com>, <richard@....at>,
<miquel.raynal@...tlin.com>, <vigneshr@...comubi_eba_copy_table>
CC: <linux-mtd@...ts.infradead.org>, <linux-kernel@...r.kernel.org>,
<yi.zhang@...wei.com>
Subject: Re: [PATCH 1/2] ubi: fix slab-out-of-bounds in
ubi_eba_get_ldesc+0xfb/0x130
Hi
> From: Guo Xuenan <guoxuenan@...wei.com>
>
> 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@...wei.com>
> Signed-off-by: ZhaoLong Wang <wangzhaolong1@...wei.com>
> ---
> 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;
>
Besides that, it's better to protect 'vol->eba_tbl->entries' assignment
like:
diff --git a/drivers/mtd/ubi/eba.c b/drivers/mtd/ubi/eba.c
index 403b79d6efd5..5ae0c1bc6f41 100644
--- a/drivers/mtd/ubi/eba.c
+++ b/drivers/mtd/ubi/eba.c
@@ -1450,7 +1450,9 @@ int ubi_eba_copy_leb(struct ubi_device *ubi, int
from, int to,
}
ubi_assert(vol->eba_tbl->entries[lnum].pnum == from);
+ spin_lock(&ubi->volumes_lock);
vol->eba_tbl->entries[lnum].pnum = to;
+ spin_unlock(&ubi->volumes_lock);
out_unlock_buf:
mutex_unlock(&ubi->buf_mutex);
Otherwise, a race between wear_leveling_work and shrinking volume could
happen:
ubi_resize_volume wear_leveling_worker
ubi_eba_copy_table(vol, new_eba_tbl, reserved_pebs);
vol->eba_tbl->entries[lnum].pnum = to;
// update old eba_tbl
vol->eba_tbl = new_eba_tbl
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