* [PATCH] btrfs: relocation: Fix KASAN report about use-after-free due to dead reloc tree cleanup race
@ 2019-09-20 2:41 Qu Wenruo
2019-09-20 21:01 ` Josef Bacik
0 siblings, 1 reply; 2+ messages in thread
From: Qu Wenruo @ 2019-09-20 2:41 UTC (permalink / raw)
To: linux-btrfs; +Cc: Cebtenzzre
[BUG]
One user reported a reproduciable KASAN report about use-after-free:
BTRFS info (device sdi1): balance: start -dvrange=1256811659264..1256811659265
BTRFS info (device sdi1): relocating block group 1256811659264 flags data|raid0
==================================================================
BUG: KASAN: use-after-free in btrfs_init_reloc_root+0x2cd/0x340 [btrfs]
Write of size 8 at addr ffff88856f671710 by task kworker/u24:10/261579
CPU: 2 PID: 261579 Comm: kworker/u24:10 Tainted: P OE 5.2.11-arch1-1-kasan #4
Hardware name: To Be Filled By O.E.M. To Be Filled By O.E.M./X99 Extreme4, BIOS P3.80 04/06/2018
Workqueue: btrfs-endio-write btrfs_endio_write_helper [btrfs]
Call Trace:
dump_stack+0x7b/0xba
print_address_description+0x6c/0x22e
? btrfs_init_reloc_root+0x2cd/0x340 [btrfs]
__kasan_report.cold+0x1b/0x3b
? btrfs_init_reloc_root+0x2cd/0x340 [btrfs]
kasan_report+0x12/0x17
__asan_report_store8_noabort+0x17/0x20
btrfs_init_reloc_root+0x2cd/0x340 [btrfs]
record_root_in_trans+0x2a0/0x370 [btrfs]
btrfs_record_root_in_trans+0xf4/0x140 [btrfs]
start_transaction+0x1ab/0xe90 [btrfs]
btrfs_join_transaction+0x1d/0x20 [btrfs]
btrfs_finish_ordered_io+0x7bf/0x18a0 [btrfs]
? lock_repin_lock+0x400/0x400
? __kmem_cache_shutdown.cold+0x140/0x1ad
? btrfs_unlink_subvol+0x9b0/0x9b0 [btrfs]
finish_ordered_fn+0x15/0x20 [btrfs]
normal_work_helper+0x1bd/0xca0 [btrfs]
? process_one_work+0x819/0x1720
? kasan_check_read+0x11/0x20
btrfs_endio_write_helper+0x12/0x20 [btrfs]
process_one_work+0x8c9/0x1720
? pwq_dec_nr_in_flight+0x2f0/0x2f0
? worker_thread+0x1d9/0x1030
worker_thread+0x98/0x1030
kthread+0x2bb/0x3b0
? process_one_work+0x1720/0x1720
? kthread_park+0x120/0x120
ret_from_fork+0x35/0x40
Allocated by task 369692:
__kasan_kmalloc.part.0+0x44/0xc0
__kasan_kmalloc.constprop.0+0xba/0xc0
kasan_kmalloc+0x9/0x10
kmem_cache_alloc_trace+0x138/0x260
btrfs_read_tree_root+0x92/0x360 [btrfs]
btrfs_read_fs_root+0x10/0xb0 [btrfs]
create_reloc_root+0x47d/0xa10 [btrfs]
btrfs_init_reloc_root+0x1e2/0x340 [btrfs]
record_root_in_trans+0x2a0/0x370 [btrfs]
btrfs_record_root_in_trans+0xf4/0x140 [btrfs]
start_transaction+0x1ab/0xe90 [btrfs]
btrfs_start_transaction+0x1e/0x20 [btrfs]
__btrfs_prealloc_file_range+0x1c2/0xa00 [btrfs]
btrfs_prealloc_file_range+0x13/0x20 [btrfs]
prealloc_file_extent_cluster+0x29f/0x570 [btrfs]
relocate_file_extent_cluster+0x193/0xc30 [btrfs]
relocate_data_extent+0x1f8/0x490 [btrfs]
relocate_block_group+0x600/0x1060 [btrfs]
btrfs_relocate_block_group+0x3a0/0xa00 [btrfs]
btrfs_relocate_chunk+0x9e/0x180 [btrfs]
btrfs_balance+0x14e4/0x2fc0 [btrfs]
btrfs_ioctl_balance+0x47f/0x640 [btrfs]
btrfs_ioctl+0x119d/0x8380 [btrfs]
do_vfs_ioctl+0x9f5/0x1060
ksys_ioctl+0x67/0x90
__x64_sys_ioctl+0x73/0xb0
do_syscall_64+0xa5/0x370
entry_SYSCALL_64_after_hwframe+0x44/0xa9
Freed by task 369692:
__kasan_slab_free+0x14f/0x210
kasan_slab_free+0xe/0x10
kfree+0xd8/0x270
btrfs_drop_snapshot+0x154c/0x1eb0 [btrfs]
clean_dirty_subvols+0x227/0x340 [btrfs]
relocate_block_group+0x972/0x1060 [btrfs]
btrfs_relocate_block_group+0x3a0/0xa00 [btrfs]
btrfs_relocate_chunk+0x9e/0x180 [btrfs]
btrfs_balance+0x14e4/0x2fc0 [btrfs]
btrfs_ioctl_balance+0x47f/0x640 [btrfs]
btrfs_ioctl+0x119d/0x8380 [btrfs]
do_vfs_ioctl+0x9f5/0x1060
ksys_ioctl+0x67/0x90
__x64_sys_ioctl+0x73/0xb0
do_syscall_64+0xa5/0x370
entry_SYSCALL_64_after_hwframe+0x44/0xa9
The buggy address belongs to the object at ffff88856f671100
which belongs to the cache kmalloc-4k of size 4096
The buggy address is located 1552 bytes inside of
4096-byte region [ffff88856f671100, ffff88856f672100)
The buggy address belongs to the page:
page:ffffea0015bd9c00 refcount:1 mapcount:0 mapping:ffff88864400e600 index:0x0 compound_mapcount: 0
flags: 0x2ffff0000010200(slab|head)
raw: 02ffff0000010200 dead000000000100 dead000000000200 ffff88864400e600
raw: 0000000000000000 0000000000070007 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
Memory state around the buggy address:
ffff88856f671600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88856f671680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88856f671700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88856f671780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88856f671800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
BTRFS info (device sdi1): 1 enospc errors during balance
BTRFS info (device sdi1): balance: ended with status: -28
[CAUSE]
The problem happens when finish_ordered_io() get called with balance
still running, while the reloc root of that subvolume is already dead.
(tree swap already done, but tree not yet deleted for possible qgroup
usage)
That means root->reloc_root still exists, but that reloc_root can be
under btrfs_drop_snapshot(), thus we shouldn't access it.
The following race could cause the use-after-free problem:
CPU1 | CPU2
--------------------------------------------------------------------------
| relocate_block_group()
| |- unset_reloc_control(rc)
| |- btrfs_commit_transaction()
btrfs_finish_ordered_io() | |- clean_dirty_subvols()
|- btrfs_join_transaction() | |
|- record_root_in_trans() | |
|- btrfs_init_reloc_root() | |
|- if (root->reloc_root) | |
| | |- root->reloc_root = NULL
| | |- btrfs_drop_snapshot(reloc_root);
|- reloc_root->last_trans|
= trans->transid |
^^^^^^^^^^^^^^^^^^^^^^
Use after free
It looks like the race window is pretty small so that it's not that easy
to trigger without the extra validation overhead introduced by KASAN.
[FIX]
Fix it by the following modifications:
- Test if the root has dead reloc tree before accessing root->reloc_root
If the root has BTRFS_ROOT_DEAD_RELOC_TREE, then we don't need to
create or update root->reloc_tree
- Clear the BTRFS_ROOT_DEAD_RELOC_TREE flag until we have fully dropped
reloc tree
To co-operate with above modification, so as long as
BTRFS_ROOT_DEAD_RELOC_TREE is still set, we won't try to re-create
reloc tree at record_root_in_trans().
Reported-by: Cebtenzzre <cebtenzzre@gmail.com>
Fixes: d2311e698578 ("btrfs: relocation: Delay reloc tree deletion after merge_reloc_roots")
Signed-off-by: Qu Wenruo <wqu@suse.com>
---
fs/btrfs/relocation.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
index 7f219851fa23..d60993a8b2ae 100644
--- a/fs/btrfs/relocation.c
+++ b/fs/btrfs/relocation.c
@@ -1434,16 +1434,19 @@ int btrfs_init_reloc_root(struct btrfs_trans_handle *trans,
int clear_rsv = 0;
int ret;
- if (root->reloc_root) {
+ if (!test_bit(BTRFS_ROOT_DEAD_RELOC_TREE, &root->state) &&
+ root->reloc_root) {
reloc_root = root->reloc_root;
reloc_root->last_trans = trans->transid;
return 0;
}
if (!rc || !rc->create_reloc_tree ||
- root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID)
+ root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID ||
+ test_bit(BTRFS_ROOT_DEAD_RELOC_TREE, &root->state))
return 0;
+
if (!trans->reloc_reserved) {
rsv = trans->block_rsv;
trans->block_rsv = rc->block_rsv;
@@ -2186,7 +2189,6 @@ static int clean_dirty_subvols(struct reloc_control *rc)
/* Merged subvolume, cleanup its reloc root */
struct btrfs_root *reloc_root = root->reloc_root;
- clear_bit(BTRFS_ROOT_DEAD_RELOC_TREE, &root->state);
list_del_init(&root->reloc_dirty_list);
root->reloc_root = NULL;
if (reloc_root) {
@@ -2195,6 +2197,7 @@ static int clean_dirty_subvols(struct reloc_control *rc)
if (ret2 < 0 && !ret)
ret = ret2;
}
+ clear_bit(BTRFS_ROOT_DEAD_RELOC_TREE, &root->state);
btrfs_put_fs_root(root);
} else {
/* Orphan reloc tree, just clean it up */
--
2.23.0
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] btrfs: relocation: Fix KASAN report about use-after-free due to dead reloc tree cleanup race
2019-09-20 2:41 [PATCH] btrfs: relocation: Fix KASAN report about use-after-free due to dead reloc tree cleanup race Qu Wenruo
@ 2019-09-20 21:01 ` Josef Bacik
0 siblings, 0 replies; 2+ messages in thread
From: Josef Bacik @ 2019-09-20 21:01 UTC (permalink / raw)
To: Qu Wenruo; +Cc: linux-btrfs, Cebtenzzre
On Fri, Sep 20, 2019 at 10:41:50AM +0800, Qu Wenruo wrote:
> [BUG]
> One user reported a reproduciable KASAN report about use-after-free:
> BTRFS info (device sdi1): balance: start -dvrange=1256811659264..1256811659265
> BTRFS info (device sdi1): relocating block group 1256811659264 flags data|raid0
> ==================================================================
> BUG: KASAN: use-after-free in btrfs_init_reloc_root+0x2cd/0x340 [btrfs]
> Write of size 8 at addr ffff88856f671710 by task kworker/u24:10/261579
>
> CPU: 2 PID: 261579 Comm: kworker/u24:10 Tainted: P OE 5.2.11-arch1-1-kasan #4
> Hardware name: To Be Filled By O.E.M. To Be Filled By O.E.M./X99 Extreme4, BIOS P3.80 04/06/2018
> Workqueue: btrfs-endio-write btrfs_endio_write_helper [btrfs]
> Call Trace:
> dump_stack+0x7b/0xba
> print_address_description+0x6c/0x22e
> ? btrfs_init_reloc_root+0x2cd/0x340 [btrfs]
> __kasan_report.cold+0x1b/0x3b
> ? btrfs_init_reloc_root+0x2cd/0x340 [btrfs]
> kasan_report+0x12/0x17
> __asan_report_store8_noabort+0x17/0x20
> btrfs_init_reloc_root+0x2cd/0x340 [btrfs]
> record_root_in_trans+0x2a0/0x370 [btrfs]
> btrfs_record_root_in_trans+0xf4/0x140 [btrfs]
> start_transaction+0x1ab/0xe90 [btrfs]
> btrfs_join_transaction+0x1d/0x20 [btrfs]
> btrfs_finish_ordered_io+0x7bf/0x18a0 [btrfs]
> ? lock_repin_lock+0x400/0x400
> ? __kmem_cache_shutdown.cold+0x140/0x1ad
> ? btrfs_unlink_subvol+0x9b0/0x9b0 [btrfs]
> finish_ordered_fn+0x15/0x20 [btrfs]
> normal_work_helper+0x1bd/0xca0 [btrfs]
> ? process_one_work+0x819/0x1720
> ? kasan_check_read+0x11/0x20
> btrfs_endio_write_helper+0x12/0x20 [btrfs]
> process_one_work+0x8c9/0x1720
> ? pwq_dec_nr_in_flight+0x2f0/0x2f0
> ? worker_thread+0x1d9/0x1030
> worker_thread+0x98/0x1030
> kthread+0x2bb/0x3b0
> ? process_one_work+0x1720/0x1720
> ? kthread_park+0x120/0x120
> ret_from_fork+0x35/0x40
>
> Allocated by task 369692:
> __kasan_kmalloc.part.0+0x44/0xc0
> __kasan_kmalloc.constprop.0+0xba/0xc0
> kasan_kmalloc+0x9/0x10
> kmem_cache_alloc_trace+0x138/0x260
> btrfs_read_tree_root+0x92/0x360 [btrfs]
> btrfs_read_fs_root+0x10/0xb0 [btrfs]
> create_reloc_root+0x47d/0xa10 [btrfs]
> btrfs_init_reloc_root+0x1e2/0x340 [btrfs]
> record_root_in_trans+0x2a0/0x370 [btrfs]
> btrfs_record_root_in_trans+0xf4/0x140 [btrfs]
> start_transaction+0x1ab/0xe90 [btrfs]
> btrfs_start_transaction+0x1e/0x20 [btrfs]
> __btrfs_prealloc_file_range+0x1c2/0xa00 [btrfs]
> btrfs_prealloc_file_range+0x13/0x20 [btrfs]
> prealloc_file_extent_cluster+0x29f/0x570 [btrfs]
> relocate_file_extent_cluster+0x193/0xc30 [btrfs]
> relocate_data_extent+0x1f8/0x490 [btrfs]
> relocate_block_group+0x600/0x1060 [btrfs]
> btrfs_relocate_block_group+0x3a0/0xa00 [btrfs]
> btrfs_relocate_chunk+0x9e/0x180 [btrfs]
> btrfs_balance+0x14e4/0x2fc0 [btrfs]
> btrfs_ioctl_balance+0x47f/0x640 [btrfs]
> btrfs_ioctl+0x119d/0x8380 [btrfs]
> do_vfs_ioctl+0x9f5/0x1060
> ksys_ioctl+0x67/0x90
> __x64_sys_ioctl+0x73/0xb0
> do_syscall_64+0xa5/0x370
> entry_SYSCALL_64_after_hwframe+0x44/0xa9
>
> Freed by task 369692:
> __kasan_slab_free+0x14f/0x210
> kasan_slab_free+0xe/0x10
> kfree+0xd8/0x270
> btrfs_drop_snapshot+0x154c/0x1eb0 [btrfs]
> clean_dirty_subvols+0x227/0x340 [btrfs]
> relocate_block_group+0x972/0x1060 [btrfs]
> btrfs_relocate_block_group+0x3a0/0xa00 [btrfs]
> btrfs_relocate_chunk+0x9e/0x180 [btrfs]
> btrfs_balance+0x14e4/0x2fc0 [btrfs]
> btrfs_ioctl_balance+0x47f/0x640 [btrfs]
> btrfs_ioctl+0x119d/0x8380 [btrfs]
> do_vfs_ioctl+0x9f5/0x1060
> ksys_ioctl+0x67/0x90
> __x64_sys_ioctl+0x73/0xb0
> do_syscall_64+0xa5/0x370
> entry_SYSCALL_64_after_hwframe+0x44/0xa9
>
> The buggy address belongs to the object at ffff88856f671100
> which belongs to the cache kmalloc-4k of size 4096
> The buggy address is located 1552 bytes inside of
> 4096-byte region [ffff88856f671100, ffff88856f672100)
> The buggy address belongs to the page:
> page:ffffea0015bd9c00 refcount:1 mapcount:0 mapping:ffff88864400e600 index:0x0 compound_mapcount: 0
> flags: 0x2ffff0000010200(slab|head)
> raw: 02ffff0000010200 dead000000000100 dead000000000200 ffff88864400e600
> raw: 0000000000000000 0000000000070007 00000001ffffffff 0000000000000000
> page dumped because: kasan: bad access detected
>
> Memory state around the buggy address:
> ffff88856f671600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff88856f671680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> >ffff88856f671700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ^
> ffff88856f671780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff88856f671800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ==================================================================
> BTRFS info (device sdi1): 1 enospc errors during balance
> BTRFS info (device sdi1): balance: ended with status: -28
>
> [CAUSE]
> The problem happens when finish_ordered_io() get called with balance
> still running, while the reloc root of that subvolume is already dead.
> (tree swap already done, but tree not yet deleted for possible qgroup
> usage)
>
> That means root->reloc_root still exists, but that reloc_root can be
> under btrfs_drop_snapshot(), thus we shouldn't access it.
>
> The following race could cause the use-after-free problem:
>
> CPU1 | CPU2
> --------------------------------------------------------------------------
> | relocate_block_group()
> | |- unset_reloc_control(rc)
> | |- btrfs_commit_transaction()
> btrfs_finish_ordered_io() | |- clean_dirty_subvols()
> |- btrfs_join_transaction() | |
> |- record_root_in_trans() | |
> |- btrfs_init_reloc_root() | |
> |- if (root->reloc_root) | |
> | | |- root->reloc_root = NULL
> | | |- btrfs_drop_snapshot(reloc_root);
> |- reloc_root->last_trans|
> = trans->transid |
> ^^^^^^^^^^^^^^^^^^^^^^
> Use after free
>
> It looks like the race window is pretty small so that it's not that easy
> to trigger without the extra validation overhead introduced by KASAN.
>
> [FIX]
> Fix it by the following modifications:
> - Test if the root has dead reloc tree before accessing root->reloc_root
> If the root has BTRFS_ROOT_DEAD_RELOC_TREE, then we don't need to
> create or update root->reloc_tree
>
> - Clear the BTRFS_ROOT_DEAD_RELOC_TREE flag until we have fully dropped
> reloc tree
> To co-operate with above modification, so as long as
> BTRFS_ROOT_DEAD_RELOC_TREE is still set, we won't try to re-create
> reloc tree at record_root_in_trans().
>
> Reported-by: Cebtenzzre <cebtenzzre@gmail.com>
> Fixes: d2311e698578 ("btrfs: relocation: Delay reloc tree deletion after merge_reloc_roots")
> Signed-off-by: Qu Wenruo <wqu@suse.com>
> ---
> fs/btrfs/relocation.c | 9 ++++++---
> 1 file changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
> index 7f219851fa23..d60993a8b2ae 100644
> --- a/fs/btrfs/relocation.c
> +++ b/fs/btrfs/relocation.c
> @@ -1434,16 +1434,19 @@ int btrfs_init_reloc_root(struct btrfs_trans_handle *trans,
> int clear_rsv = 0;
> int ret;
>
> - if (root->reloc_root) {
> + if (!test_bit(BTRFS_ROOT_DEAD_RELOC_TREE, &root->state) &&
> + root->reloc_root) {
> reloc_root = root->reloc_root;
> reloc_root->last_trans = trans->transid;
> return 0;
> }
>
> if (!rc || !rc->create_reloc_tree ||
> - root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID)
> + root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID ||
> + test_bit(BTRFS_ROOT_DEAD_RELOC_TREE, &root->state))
> return 0;
Just move this bit above the root->reloc_root check, and drop the extra test_bit
in the above check.
>
> +
Random newline. The rest seems fine. Thanks,
Josef
^ permalink raw reply [flat|nested] 2+ messages in thread
end of thread, other threads:[~2019-09-20 21:01 UTC | newest]
Thread overview: 2+ messages (download: mbox.gz / follow: Atom feed)
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2019-09-20 2:41 [PATCH] btrfs: relocation: Fix KASAN report about use-after-free due to dead reloc tree cleanup race Qu Wenruo
2019-09-20 21:01 ` Josef Bacik
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