4.19-stable review patch. If anyone has any objections, please let me know.
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From: Pan Bian bianpan2016@163.com
commit 42a657f57628402c73237547f0134e083e2f6764 upstream.
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@vger.kernel.org # 4.4+ Reviewed-by: Qu Wenruo wqu@suse.com Signed-off-by: Pan Bian bianpan2016@163.com Reviewed-by: David Sterba dsterba@suse.com Signed-off-by: David Sterba dsterba@suse.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- fs/btrfs/relocation.c | 1 + 1 file changed, 1 insertion(+)
--- a/fs/btrfs/relocation.c +++ b/fs/btrfs/relocation.c @@ -3963,6 +3963,7 @@ static noinline_for_stack int relocate_b restart: if (update_backref_cache(trans, &rc->backref_cache)) { btrfs_end_transaction(trans); + trans = NULL; continue; }