[PATCH 5.9 505/757] afs: Fix cell removal

Greg Kroah-Hartman
2020-10-27T16:48:35Z

From: David Howells <dhowells@redhat.com>

[ Upstream commit 1d0e850a49a5b56f8f3cb51e74a11e2fedb96be6 ]

Fix cell removal by inserting a more final state than AFS_CELL_FAILED that
indicates that the cell has been unpublished in case the manager is already
requeued and will go through again. The new AFS_CELL_REMOVED state will
just immediately leave the manager function.

Going through a second time in the AFS_CELL_FAILED state will cause it to
try to remove the cell again, potentially leading to the proc list being
removed.

Fixes: 989782dcdc91 ("afs: Overhaul cell database management")
Reported-by: syzbot+b994ecf2b023f14832c1@syzkaller.appspotmail.com
Reported-by: syzbot+0e0db88e1eb44a91ae8d@syzkaller.appspotmail.com
Reported-by: syzbot+2d0585e5efcd43d113c2@syzkaller.appspotmail.com
Reported-by: syzbot+1ecc2f9d3387f1d79d42@syzkaller.appspotmail.com
Reported-by: syzbot+18d51774588492bf3f69@syzkaller.appspotmail.com
Reported-by: syzbot+a5e4946b04d6ca8fa5f3@syzkaller.appspotmail.com
Suggested-by: Hillf Danton <hdanton@sina.com>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Hillf Danton <hdanton@sina.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/afs/cell.c | 16 ++++++++++------
fs/afs/internal.h | 1 +
2 files changed, 11 insertions(+), 6 deletions(-)

diff --git a/fs/afs/cell.c b/fs/afs/cell.c
index 1944be78e9b0d..bc7ed46aaca9f 100644
--- a/fs/afs/cell.c
+++ b/fs/afs/cell.c
@@ -291,11 +291,11 @@ struct afs_cell *afs_lookup_cell(struct afs_net *net,
wait_var_event(&cell->state,
({
state = smp_load_acquire(&cell->state); /* vs error */
- state == AFS_CELL_ACTIVE || state == AFS_CELL_FAILED;
+ state == AFS_CELL_ACTIVE || state == AFS_CELL_REMOVED;
}));

/* Check the state obtained from the wait check. */
- if (state == AFS_CELL_FAILED) {
+ if (state == AFS_CELL_REMOVED) {
ret = cell->error;
goto error;
}
@@ -700,7 +700,6 @@ static void afs_deactivate_cell(struct afs_net *net, struct afs_cell *cell)
static void afs_manage_cell(struct afs_cell *cell)
{
struct afs_net *net = cell->net;
- bool deleted;
int ret, active;

_enter("%s", cell->name);
@@ -712,13 +711,15 @@ static void afs_manage_cell(struct afs_cell *cell)
case AFS_CELL_FAILED:
down_write(&net->cells_lock);
active = 1;
- deleted = atomic_try_cmpxchg_relaxed(&cell->active, &active, 0);
- if (deleted) {
+ if (atomic_try_cmpxchg_relaxed(&cell->active, &active, 0)) {
rb_erase(&cell->net_node, &net->cells);
+ smp_store_release(&cell->state, AFS_CELL_REMOVED);
}
up_write(&net->cells_lock);
- if (deleted)
+ if (cell->state == AFS_CELL_REMOVED) {
+ wake_up_var(&cell->state);
goto final_destruction;
+ }
if (cell->state == AFS_CELL_FAILED)
goto done;
smp_store_release(&cell->state, AFS_CELL_UNSET);
@@ -760,6 +761,9 @@ static void afs_manage_cell(struct afs_cell *cell)
wake_up_var(&cell->state);
goto again;

+ case AFS_CELL_REMOVED:
+ goto done;
+
default:
break;
}
diff --git a/fs/afs/internal.h b/fs/afs/internal.h
index 0363511290c8d..06e617ee4cd1e 100644
--- a/fs/afs/internal.h
+++ b/fs/afs/internal.h
@@ -326,6 +326,7 @@ enum afs_cell_state {
AFS_CELL_DEACTIVATING,
AFS_CELL_INACTIVE,
AFS_CELL_FAILED,
+ AFS_CELL_REMOVED,
};

/*
--
2.25.1