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afs: Fix lack of locking around modifications of net->cells_dyn_ino

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Fix the lack of locking around modifications of net->cells_dyn_ino by
taking net->cells_lock exclusively.  This also requires to cell to be
removed from net->cells_dyn_ino in afs_destroy_cell_work() rather than in
afs_cell_destroy() as the latter runs in RCU cleanup context and sleeping
locks cannot be taken there.

Fixes: 1d0b929fc0 ("afs: Change dynroot to create contents on demand")
Closes: https://sashiko.dev/#/patchset/20260618074903.2374756-1-dhowells%40redhat.com
Signed-off-by: David Howells <dhowells@redhat.com>
Link: https://patch.msgid.link/20260622090856.2746629-19-dhowells@redhat.com
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
This commit is contained in:
David Howells
2026-06-22 10:08:52 +01:00
committed by Christian Brauner
parent fc10c0ecf0
commit 55e841836c
2 changed files with 8 additions and 2 deletions
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8
fs/afs/cell.c
View File

@@ -205,8 +205,10 @@ static struct afs_cell *afs_alloc_cell(struct afs_net *net,
cell->dns_source = vllist->source;
cell->dns_status = vllist->status;
smp_store_release(&cell->dns_lookup_count, 1); /* vs source/status */
down_write(&net->cells_lock);
ret = idr_alloc_cyclic(&net->cells_dyn_ino, cell,
2, INT_MAX / 2, GFP_KERNEL);
up_write(&net->cells_lock);
if (ret < 0)
goto error;
atomic_inc(&net->cells_outstanding);
@@ -579,7 +581,6 @@ static void afs_cell_destroy(struct rcu_head *rcu)
afs_put_vlserverlist(net, rcu_access_pointer(cell->vl_servers));
afs_unuse_cell(cell->alias_of, afs_cell_trace_unuse_alias);
key_put(cell->anonymous_key);
idr_remove(&net->cells_dyn_ino, cell->dynroot_ino);
kfree(cell->name - 1);
kfree(cell);
@@ -594,6 +595,11 @@ static void afs_destroy_cell_work(struct work_struct *work)
afs_see_cell(cell, afs_cell_trace_destroy);
timer_delete_sync(&cell->management_timer);
cancel_work_sync(&cell->manager);
down_write(&cell->net->cells_lock);
idr_remove(&cell->net->cells_dyn_ino, cell->dynroot_ino);
up_write(&cell->net->cells_lock);
call_rcu(&cell->rcu, afs_cell_destroy);
}

2
fs/afs/dynroot.c
View File

@@ -278,7 +278,7 @@ static struct dentry *afs_lookup_atcell(struct inode *dir, struct dentry *dentry
}
/*
* Transcribe the cell database into readdir content under the RCU read lock.
* Transcribe the cell database into readdir content under net->cells_lock.
* Each cell produces two entries, one prefixed with a dot and one not.
*/
static int afs_dynroot_readdir_cells(struct afs_net *net, struct dir_context *ctx)