2023-05-19 21:19:48

by Anna Schumaker

[permalink] [raw]
Subject: [PATCH] NFSv4.2: Fix a potential double free with READ_PLUS

From: Anna Schumaker <[email protected]>

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 <[email protected]>
---
fs/nfs/nfs4proc.c | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 18f25ff4bff7..d3665390c4cb 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -5437,10 +5437,18 @@ 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))
--
2.40.1