The patch below does not apply to the 4.9-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@xxxxxxxxxxxxxxx>.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
>From 42a657f57628402c73237547f0134e083e2f6764 Mon Sep 17 00:00:00 2001
From: Pan Bian <bianpan2016@xxxxxxx>
Date: Fri, 23 Nov 2018 18:10:15 +0800
Subject: [PATCH] btrfs: relocation: set trans to be NULL after ending
transaction
The function relocate_block_group calls btrfs_end_transaction to release
trans when update_backref_cache returns 1, and then continues the loop
body. If btrfs_block_rsv_refill fails this time, it will jump out the
loop and the freed trans will be accessed. This may result in a
use-after-free bug. The patch assigns NULL to trans after trans is
released so that it will not be accessed.
Fixes: 0647bf564f1 ("Btrfs: improve forever loop when doing balance relocation")
CC: stable@xxxxxxxxxxxxxxx # 4.4+
Reviewed-by: Qu Wenruo <wqu@xxxxxxxx>
Signed-off-by: Pan Bian <bianpan2016@xxxxxxx>
Reviewed-by: David Sterba <dsterba@xxxxxxxx>
Signed-off-by: David Sterba <dsterba@xxxxxxxx>
diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
index 924116f654a1..a3f75b8926d4 100644
--- a/fs/btrfs/relocation.c
+++ b/fs/btrfs/relocation.c
@@ -3959,6 +3959,7 @@ static noinline_for_stack int relocate_block_group(struct reloc_control *rc)
restart:
if (update_backref_cache(trans, &rc->backref_cache)) {
btrfs_end_transaction(trans);
+ trans = NULL;
continue;
}
