From: "J. Bruce Fields" <bfields@xxxxxxxxxx>
The pool_to and to_pool fields of the global svc_pool_map are freed on
shutdown, but are initialized in nfsd startup only in the
SVC_POOL_PERCPU and SVC_POOL_PERNODE cases.
They *are* initialized to zero on kernel startup. So as long as you use
only SVC_POOL_GLOBAL (the default), this will never be a problem.
You're also OK if you only ever use SVC_POOL_PERCPU or SVC_POOL_PERNODE.
However, the following sequence events leads to a double-free:
1. set SVC_POOL_PERCPU or SVC_POOL_PERNODE
2. start nfsd: both fields are initialized.
3. shutdown nfsd: both fields are freed.
4. set SVC_POOL_GLOBAL
5. start nfsd: the fields are left untouched.
6. shutdown nfsd: now we try to free them again.
Step 4 is actually unnecessary, since (for some bizarre reason), nfsd
automatically resets the pool mode to SVC_POOL_GLOBAL on shutdown.
Signed-off-by: J. Bruce Fields <bfields@xxxxxxxxxx>
---
net/sunrpc/svc.c | 3 +++
1 files changed, 3 insertions(+), 0 deletions(-)
diff --git a/net/sunrpc/svc.c b/net/sunrpc/svc.c
index e9632bb..1dd5fd0 100644
--- a/net/sunrpc/svc.c
+++ b/net/sunrpc/svc.c
@@ -167,6 +167,7 @@ svc_pool_map_alloc_arrays(struct svc_pool_map *m, unsigned int maxpools)
fail_free:
kfree(m->to_pool);
+ m->to_pool = NULL;
fail:
return -ENOMEM;
}
@@ -287,7 +288,9 @@ svc_pool_map_put(void)
if (!--m->count) {
m->mode = SVC_POOL_DEFAULT;
kfree(m->to_pool);
+ m->to_pool = NULL;
kfree(m->pool_to);
+ m->pool_to = NULL;
m->npools = 0;
}
--
1.7.5.4
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