Your patch needs a bit of adjustment. The check must be done inside the write
lock on afs_cells_sem otherwise there's a race.
David
---
AFS: prevent double cell registration
From: Sven Schnelle <svens@xxxxxxxxxxxxxx>
kafs doesn't check if the cell already exists - so if you do an
echo "add newcell.org 1.2.3.4" >/proc/fs/afs/cells it will try to
create this cell again. kobject will also complain about a double
registration. To prevent such problems, return -EEXIST in that case.
Signed-off-by: Sven Schnelle <svens@xxxxxxxxxxxxxx>
Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
---
fs/afs/cell.c | 15 +++++++++++++--
1 files changed, 13 insertions(+), 2 deletions(-)
diff --git a/fs/afs/cell.c b/fs/afs/cell.c
index 970d38f..788865d 100644
--- a/fs/afs/cell.c
+++ b/fs/afs/cell.c
@@ -127,14 +127,20 @@ struct afs_cell *afs_cell_create(const char *name, char *vllist)
_enter("%s,%s", name, vllist);
+ down_write(&afs_cells_sem);
+ read_lock(&afs_cells_lock);
+ list_for_each_entry(cell, &afs_cells, link) {
+ if (strcasecmp(cell->name, name) == 0)
+ goto duplicate_name;
+ }
+ read_unlock(&afs_cells_lock);
+
cell = afs_cell_alloc(name, vllist);
if (IS_ERR(cell)) {
_leave(" = %ld", PTR_ERR(cell));
return cell;
}
- down_write(&afs_cells_sem);
-
/* add a proc directory for this cell */
ret = afs_proc_cell_setup(cell);
if (ret < 0)
@@ -167,6 +173,11 @@ error:
kfree(cell);
_leave(" = %d", ret);
return ERR_PTR(ret);
+
+duplicate_name:
+ read_unlock(&afs_cells_lock);
+ up_write(&afs_cells_sem);
+ return ERR_PTR(-EEXIST);
}
/*
--
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