This is a note to let you know that I've just added the patch titled
btrfs: unset reloc control if transaction commit fails in prepare_to_relocate()
to the 5.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
btrfs-unset-reloc-control-if-transaction-commit-fails-in-prepare_to_relocate.patch
and it can be found in the queue-5.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 85f02d6c856b9f3a0acf5219de6e32f58b9778eb Mon Sep 17 00:00:00 2001
From: Zixuan Fu <r33s3n6@xxxxxxxxx>
Date: Thu, 21 Jul 2022 15:48:29 +0800
Subject: btrfs: unset reloc control if transaction commit fails in prepare_to_relocate()
From: Zixuan Fu <r33s3n6@xxxxxxxxx>
commit 85f02d6c856b9f3a0acf5219de6e32f58b9778eb upstream.
In btrfs_relocate_block_group(), the rc is allocated. Then
btrfs_relocate_block_group() calls
relocate_block_group()
prepare_to_relocate()
set_reloc_control()
that assigns rc to the variable fs_info->reloc_ctl. When
prepare_to_relocate() returns, it calls
btrfs_commit_transaction()
btrfs_start_dirty_block_groups()
btrfs_alloc_path()
kmem_cache_zalloc()
which may fail for example (or other errors could happen). When the
failure occurs, btrfs_relocate_block_group() detects the error and frees
rc and doesn't set fs_info->reloc_ctl to NULL. After that, in
btrfs_init_reloc_root(), rc is retrieved from fs_info->reloc_ctl and
then used, which may cause a use-after-free bug.
This possible bug can be triggered by calling btrfs_ioctl_balance()
before calling btrfs_ioctl_defrag().
To fix this possible bug, in prepare_to_relocate(), check if
btrfs_commit_transaction() fails. If the failure occurs,
unset_reloc_control() is called to set fs_info->reloc_ctl to NULL.
The error log in our fault-injection testing is shown as follows:
[ 58.751070] BUG: KASAN: use-after-free in btrfs_init_reloc_root+0x7ca/0x920 [btrfs]
...
[ 58.753577] Call Trace:
...
[ 58.755800] kasan_report+0x45/0x60
[ 58.756066] btrfs_init_reloc_root+0x7ca/0x920 [btrfs]
[ 58.757304] record_root_in_trans+0x792/0xa10 [btrfs]
[ 58.757748] btrfs_record_root_in_trans+0x463/0x4f0 [btrfs]
[ 58.758231] start_transaction+0x896/0x2950 [btrfs]
[ 58.758661] btrfs_defrag_root+0x250/0xc00 [btrfs]
[ 58.759083] btrfs_ioctl_defrag+0x467/0xa00 [btrfs]
[ 58.759513] btrfs_ioctl+0x3c95/0x114e0 [btrfs]
...
[ 58.768510] Allocated by task 23683:
[ 58.768777] ____kasan_kmalloc+0xb5/0xf0
[ 58.769069] __kmalloc+0x227/0x3d0
[ 58.769325] alloc_reloc_control+0x10a/0x3d0 [btrfs]
[ 58.769755] btrfs_relocate_block_group+0x7aa/0x1e20 [btrfs]
[ 58.770228] btrfs_relocate_chunk+0xf1/0x760 [btrfs]
[ 58.770655] __btrfs_balance+0x1326/0x1f10 [btrfs]
[ 58.771071] btrfs_balance+0x3150/0x3d30 [btrfs]
[ 58.771472] btrfs_ioctl_balance+0xd84/0x1410 [btrfs]
[ 58.771902] btrfs_ioctl+0x4caa/0x114e0 [btrfs]
...
[ 58.773337] Freed by task 23683:
...
[ 58.774815] kfree+0xda/0x2b0
[ 58.775038] free_reloc_control+0x1d6/0x220 [btrfs]
[ 58.775465] btrfs_relocate_block_group+0x115c/0x1e20 [btrfs]
[ 58.775944] btrfs_relocate_chunk+0xf1/0x760 [btrfs]
[ 58.776369] __btrfs_balance+0x1326/0x1f10 [btrfs]
[ 58.776784] btrfs_balance+0x3150/0x3d30 [btrfs]
[ 58.777185] btrfs_ioctl_balance+0xd84/0x1410 [btrfs]
[ 58.777621] btrfs_ioctl+0x4caa/0x114e0 [btrfs]
...
Reported-by: TOTE Robot <oslab@xxxxxxxxxxxxxxx>
CC: stable@xxxxxxxxxxxxxxx # 5.15+
Reviewed-by: Sweet Tea Dorminy <sweettea-kernel@xxxxxxxxxx>
Reviewed-by: Nikolay Borisov <nborisov@xxxxxxxx>
Signed-off-by: Zixuan Fu <r33s3n6@xxxxxxxxx>
Signed-off-by: David Sterba <dsterba@xxxxxxxx>
Signed-off-by: Stefan Ghinea <stefan.ghinea@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/btrfs/relocation.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
--- a/fs/btrfs/relocation.c
+++ b/fs/btrfs/relocation.c
@@ -4102,7 +4102,12 @@ int prepare_to_relocate(struct reloc_con
*/
return PTR_ERR(trans);
}
- return btrfs_commit_transaction(trans);
+
+ ret = btrfs_commit_transaction(trans);
+ if (ret)
+ unset_reloc_control(rc);
+
+ return ret;
}
static noinline_for_stack int relocate_block_group(struct reloc_control *rc)
Patches currently in stable-queue which might be from r33s3n6@xxxxxxxxx are
queue-5.4/btrfs-unset-reloc-control-if-transaction-commit-fails-in-prepare_to_relocate.patch
