diff options
| author | David Howells <dhowells@redhat.com> | 2025-03-06 08:46:57 +0000 |
|---|---|---|
| committer | David Howells <dhowells@redhat.com> | 2025-03-10 09:46:53 +0000 |
| commit | 823869e1e61607ab0d433de3c8abed221dc80a5e (patch) | |
| tree | d2b170a71004d62824f7c6cb88dc06fbe7ffefe6 /fs/afs/cell.c | |
| parent | 1e15510b71c99c6e49134d756df91069f7d18141 (diff) | |
afs: Fix afs_atcell_get_link() to handle RCU pathwalk
The ->get_link() method may be entered under RCU pathwalk conditions (in
which case, the dentry pointer is NULL). This is not taken account of by
afs_atcell_get_link() and lockdep will complain when it tries to lock an
rwsem.
Fix this by marking net->ws_cell as __rcu and using RCU access macros on it
and by making afs_atcell_get_link() just return a pointer to the name in
RCU pathwalk without taking net->cells_lock or a ref on the cell as RCU
will protect the name storage (the cell is already freed via call_rcu()).
Fixes: 30bca65bbbae ("afs: Make /afs/@cell and /afs/.@cell symlinks")
Reported-by: Alexander Viro <viro@zeniv.linux.org.uk>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
cc: linux-fsdevel@vger.kernel.org
Link: https://lore.kernel.org/r/20250310094206.801057-2-dhowells@redhat.com/ # v4
Diffstat (limited to 'fs/afs/cell.c')
| -rw-r--r-- | fs/afs/cell.c | 11 |
1 files changed, 6 insertions, 5 deletions
diff --git a/fs/afs/cell.c b/fs/afs/cell.c index cee42646736c..96a6781f3653 100644 --- a/fs/afs/cell.c +++ b/fs/afs/cell.c @@ -64,7 +64,8 @@ static struct afs_cell *afs_find_cell_locked(struct afs_net *net, return ERR_PTR(-ENAMETOOLONG); if (!name) { - cell = net->ws_cell; + cell = rcu_dereference_protected(net->ws_cell, + lockdep_is_held(&net->cells_lock)); if (!cell) return ERR_PTR(-EDESTADDRREQ); goto found; @@ -388,8 +389,8 @@ int afs_cell_init(struct afs_net *net, const char *rootcell) /* install the new cell */ down_write(&net->cells_lock); afs_see_cell(new_root, afs_cell_trace_see_ws); - old_root = net->ws_cell; - net->ws_cell = new_root; + old_root = rcu_replace_pointer(net->ws_cell, new_root, + lockdep_is_held(&net->cells_lock)); up_write(&net->cells_lock); afs_unuse_cell(net, old_root, afs_cell_trace_unuse_ws); @@ -945,8 +946,8 @@ void afs_cell_purge(struct afs_net *net) _enter(""); down_write(&net->cells_lock); - ws = net->ws_cell; - net->ws_cell = NULL; + ws = rcu_replace_pointer(net->ws_cell, NULL, + lockdep_is_held(&net->cells_lock)); up_write(&net->cells_lock); afs_unuse_cell(net, ws, afs_cell_trace_unuse_ws); |