Commit 42a657f5 authored by Pan Bian's avatar Pan Bian Committed by David Sterba
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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: 0647bf56

 ("Btrfs: improve forever loop when doing balance relocation")
CC: # 4.4+
Reviewed-by: default avatarQu Wenruo <>
Signed-off-by: default avatarPan Bian <>
Reviewed-by: default avatarDavid Sterba <>
Signed-off-by: default avatarDavid Sterba <>
parent 552f0329
......@@ -3959,6 +3959,7 @@ static noinline_for_stack int relocate_block_group(struct reloc_control *rc)
if (update_backref_cache(trans, &rc->backref_cache)) {
trans = NULL;
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