NFSv4.2: Fix a potential double free with READ_PLUS

commit 43439d858bbae244a510de47f9a55f667ca4ed52 upstream.

kfree()-ing the scratch page isn't enough, we also need to set the pointer
back to NULL to avoid a double-free in the case of a resend.

Fixes: fbd2a05f29a9 (NFSv4.2: Rework scratch handling for READ_PLUS)
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 3f96ccc..b707a23 100644 (file)
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -5444,10 +5444,18 @@ static bool nfs4_read_plus_not_supported(struct rpc_task *task,
        return false;
 }
 
-static int nfs4_read_done(struct rpc_task *task, struct nfs_pgio_header *hdr)
+static inline void nfs4_read_plus_scratch_free(struct nfs_pgio_header *hdr)
 {
-       if (hdr->res.scratch)
+       if (hdr->res.scratch) {
                kfree(hdr->res.scratch);
+               hdr->res.scratch = NULL;
+       }
+}
+
+static int nfs4_read_done(struct rpc_task *task, struct nfs_pgio_header *hdr)
+{
+       nfs4_read_plus_scratch_free(hdr);
+
        if (!nfs4_sequence_done(task, &hdr->res.seq_res))
                return -EAGAIN;
        if (nfs4_read_stateid_changed(task, &hdr->args))