[PATCH AUTOSEL 4.19 44/45] afs: Fix leak in afs_lookup_cell_rcu()

Sasha Levin
2019-08-29T18:23:30Z

From: David Howells <dhowells@redhat.com>

[ Upstream commit a5fb8e6c02d6a518fb2b1a2b8c2471fa77b69436 ]

Fix a leak on the cell refcount in afs_lookup_cell_rcu() due to
non-clearance of the default error in the case a NULL cell name is passed
and the workstation default cell is used.

Also put a bit at the end to make sure we don't leak a cell ref if we're
going to be returning an error.

This leak results in an assertion like the following when the kafs module is
unloaded:

AFS: Assertion failed
2 == 1 is false
0x2 == 0x1 is false
------------[ cut here ]------------
kernel BUG at fs/afs/cell.c:770!
...
RIP: 0010:afs_manage_cells+0x220/0x42f [kafs]
...
process_one_work+0x4c2/0x82c
? pool_mayday_timeout+0x1e1/0x1e1
? do_raw_spin_lock+0x134/0x175
worker_thread+0x336/0x4a6
? rescuer_thread+0x4af/0x4af
kthread+0x1de/0x1ee
? kthread_park+0xd4/0xd4
ret_from_fork+0x24/0x30

Fixes: 989782dcdc91 ("afs: Overhaul cell database management")
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/afs/cell.c | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/fs/afs/cell.c b/fs/afs/cell.c
index 6127f0fcd62c4..ee07162d35c7a 100644
--- a/fs/afs/cell.c
+++ b/fs/afs/cell.c
@@ -76,6 +76,7 @@ struct afs_cell *afs_lookup_cell_rcu(struct afs_net *net,
cell = rcu_dereference_raw(net->ws_cell);
if (cell) {
afs_get_cell(cell);
+ ret = 0;
break;
}
ret = -EDESTADDRREQ;
@@ -110,6 +111,9 @@ struct afs_cell *afs_lookup_cell_rcu(struct afs_net *net,

done_seqretry(&net->cells_lock, seq);

+ if (ret != 0 && cell)
+ afs_put_cell(net, cell);
+
return ret == 0 ? cell : ERR_PTR(ret);
}

--
2.20.1