6.8-stable review patch. If anyone has any objections, please let me know.
------------------
From: Johannes Thumshirn <johannes.thumshirn@xxxxxxx>
commit 1ec17ef59168a1a6f1105f5dc517f783839a5302 upstream.
Shinichiro reported the following use-after-free triggered by the device
replace operation in fstests btrfs/070.
BTRFS info (device nullb1): scrub: finished on devid 1 with status: 0
==================================================================
BUG: KASAN: slab-use-after-free in do_zone_finish+0x91a/0xb90 [btrfs]
Read of size 8 at addr ffff8881543c8060 by task btrfs-cleaner/3494007
CPU: 0 PID: 3494007 Comm: btrfs-cleaner Tainted: G W 6.8.0-rc5-kts #1
Hardware name: Supermicro Super Server/X11SPi-TF, BIOS 3.3 02/21/2020
Call Trace:
<TASK>
dump_stack_lvl+0x5b/0x90
print_report+0xcf/0x670
? __virt_addr_valid+0x200/0x3e0
kasan_report+0xd8/0x110
? do_zone_finish+0x91a/0xb90 [btrfs]
? do_zone_finish+0x91a/0xb90 [btrfs]
do_zone_finish+0x91a/0xb90 [btrfs]
btrfs_delete_unused_bgs+0x5e1/0x1750 [btrfs]
? __pfx_btrfs_delete_unused_bgs+0x10/0x10 [btrfs]
? btrfs_put_root+0x2d/0x220 [btrfs]
? btrfs_clean_one_deleted_snapshot+0x299/0x430 [btrfs]
cleaner_kthread+0x21e/0x380 [btrfs]
? __pfx_cleaner_kthread+0x10/0x10 [btrfs]
kthread+0x2e3/0x3c0
? __pfx_kthread+0x10/0x10
ret_from_fork+0x31/0x70
? __pfx_kthread+0x10/0x10
ret_from_fork_asm+0x1b/0x30
</TASK>
Allocated by task 3493983:
kasan_save_stack+0x33/0x60
kasan_save_track+0x14/0x30
__kasan_kmalloc+0xaa/0xb0
btrfs_alloc_device+0xb3/0x4e0 [btrfs]
device_list_add.constprop.0+0x993/0x1630 [btrfs]
btrfs_scan_one_device+0x219/0x3d0 [btrfs]
btrfs_control_ioctl+0x26e/0x310 [btrfs]
__x64_sys_ioctl+0x134/0x1b0
do_syscall_64+0x99/0x190
entry_SYSCALL_64_after_hwframe+0x6e/0x76
Freed by task 3494056:
kasan_save_stack+0x33/0x60
kasan_save_track+0x14/0x30
kasan_save_free_info+0x3f/0x60
poison_slab_object+0x102/0x170
__kasan_slab_free+0x32/0x70
kfree+0x11b/0x320
btrfs_rm_dev_replace_free_srcdev+0xca/0x280 [btrfs]
btrfs_dev_replace_finishing+0xd7e/0x14f0 [btrfs]
btrfs_dev_replace_by_ioctl+0x1286/0x25a0 [btrfs]
btrfs_ioctl+0xb27/0x57d0 [btrfs]
__x64_sys_ioctl+0x134/0x1b0
do_syscall_64+0x99/0x190
entry_SYSCALL_64_after_hwframe+0x6e/0x76
The buggy address belongs to the object at ffff8881543c8000
which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 96 bytes inside of
freed 1024-byte region [ffff8881543c8000, ffff8881543c8400)
The buggy address belongs to the physical page:
page:00000000fe2c1285 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1543c8
head:00000000fe2c1285 order:3 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0x17ffffc0000840(slab|head|node=0|zone=2|lastcpupid=0x1fffff)
page_type: 0xffffffff()
raw: 0017ffffc0000840 ffff888100042dc0 ffffea0019e8f200 dead000000000002
raw: 0000000000000000 0000000000100010 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
Memory state around the buggy address:
ffff8881543c7f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff8881543c7f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff8881543c8000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff8881543c8080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8881543c8100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
This UAF happens because we're accessing stale zone information of a
already removed btrfs_device in do_zone_finish().
The sequence of events is as follows:
btrfs_dev_replace_start
btrfs_scrub_dev
btrfs_dev_replace_finishing
btrfs_dev_replace_update_device_in_mapping_tree <-- devices replaced
btrfs_rm_dev_replace_free_srcdev
btrfs_free_device <-- device freed
cleaner_kthread
btrfs_delete_unused_bgs
btrfs_zone_finish
do_zone_finish <-- refers the freed device
The reason for this is that we're using a cached pointer to the chunk_map
from the block group, but on device replace this cached pointer can
contain stale device entries.
The staleness comes from the fact, that btrfs_block_group::physical_map is
not a pointer to a btrfs_chunk_map but a memory copy of it.
Also take the fs_info::dev_replace::rwsem to prevent
btrfs_dev_replace_update_device_in_mapping_tree() from changing the device
underneath us again.
Note: btrfs_dev_replace_update_device_in_mapping_tree() is holding
fs_info::mapping_tree_lock, but as this is a spinning read/write lock we
cannot take it as the call to blkdev_zone_mgmt() requires a memory
allocation which may not sleep.
But btrfs_dev_replace_update_device_in_mapping_tree() is always called with
the fs_info::dev_replace::rwsem held in write mode.
Many thanks to Shinichiro for analyzing the bug.
Reported-by: Shinichiro Kawasaki <shinichiro.kawasaki@xxxxxxx>
CC: stable@xxxxxxxxxxxxxxx # 6.8
Reviewed-by: Filipe Manana <fdmanana@xxxxxxxx>
Signed-off-by: Johannes Thumshirn <johannes.thumshirn@xxxxxxx>
Reviewed-by: David Sterba <dsterba@xxxxxxxx>
Signed-off-by: David Sterba <dsterba@xxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/btrfs/zoned.c | 14 +++++++-------
1 file changed, 7 insertions(+), 7 deletions(-)
--- a/fs/btrfs/zoned.c
+++ b/fs/btrfs/zoned.c
@@ -1563,11 +1563,7 @@ int btrfs_load_block_group_zone_info(str
if (!map)
return -EINVAL;
- cache->physical_map = btrfs_clone_chunk_map(map, GFP_NOFS);
- if (!cache->physical_map) {
- ret = -ENOMEM;
- goto out;
- }
+ cache->physical_map = map;
zone_info = kcalloc(map->num_stripes, sizeof(*zone_info), GFP_NOFS);
if (!zone_info) {
@@ -1679,7 +1675,6 @@ out:
}
bitmap_free(active);
kfree(zone_info);
- btrfs_free_chunk_map(map);
return ret;
}
@@ -2164,6 +2159,7 @@ static int do_zone_finish(struct btrfs_b
struct btrfs_chunk_map *map;
const bool is_metadata = (block_group->flags &
(BTRFS_BLOCK_GROUP_METADATA | BTRFS_BLOCK_GROUP_SYSTEM));
+ struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
int ret = 0;
int i;
@@ -2239,6 +2235,7 @@ static int do_zone_finish(struct btrfs_b
btrfs_clear_data_reloc_bg(block_group);
spin_unlock(&block_group->lock);
+ down_read(&dev_replace->rwsem);
map = block_group->physical_map;
for (i = 0; i < map->num_stripes; i++) {
struct btrfs_device *device = map->stripes[i].dev;
@@ -2253,13 +2250,16 @@ static int do_zone_finish(struct btrfs_b
zinfo->zone_size >> SECTOR_SHIFT,
GFP_NOFS);
- if (ret)
+ if (ret) {
+ up_read(&dev_replace->rwsem);
return ret;
+ }
if (!(block_group->flags & BTRFS_BLOCK_GROUP_DATA))
zinfo->reserved_active_zones++;
btrfs_dev_clear_active_zone(device, physical);
}
+ up_read(&dev_replace->rwsem);
if (!fully_written)
btrfs_dec_block_group_ro(block_group);
