[PATCH 5.10/5.15] NFSv4.1: zero referring call lists before decoding

[Mikhail Dmitrichenko]

From: Jérémy Jean <Jeremy.Jean@xxxxxxxxxxxxxxxxx>

commit 8fa4804fe62ca4155a2d8fc2789d630376cbf2fc upstream.

decode_cb_sequence_args() allocates csa_rclists with kmalloc_objs(), so
each referring_call_list starts uninitialized. decode_rc_list() assigns
rcl_refcalls only when rcl_nrefcalls is nonzero. A valid list with zero
referring calls therefore leaves the pointer uninitialized, and
nfs4_callback_sequence() later passes stale slab contents to kfree().

Allocate csa_rclists with kzalloc_objs() so every rcl_refcalls member is
NULL from the beginning, including valid empty referring call lists.

Fixes: 4aece6a19cf7 ("nfs41: cb_sequence xdr implementation")
Assisted-by: Codex:gpt-5
Signed-off-by: Jérémy Jean <Jeremy.Jean@xxxxxxxxxxxxxxxxx>
Signed-off-by: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
[ mdmitrichenko: kzalloc_objs() does not exist in 5.10 and 5.15, so
  replace the kmalloc_array() call with kcalloc() instead. ]
Signed-off-by: Mikhail Dmitrichenko <mdmitrichenko@xxxxxxxxxxxxx>
---
Backport fix for CVE-2026-90104
 fs/nfs/callback_xdr.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/fs/nfs/callback_xdr.c b/fs/nfs/callback_xdr.c
index c8f5a0555ad2..cc9a19467b88 100644
--- a/fs/nfs/callback_xdr.c
+++ b/fs/nfs/callback_xdr.c
@@ -419,9 +419,9 @@ static __be32 decode_cb_sequence_args(struct svc_rqst *rqstp,
 	args->csa_nrclists = ntohl(*p++);
 	args->csa_rclists = NULL;
 	if (args->csa_nrclists) {
-		args->csa_rclists = kmalloc_array(args->csa_nrclists,
-						  sizeof(*args->csa_rclists),
-						  GFP_KERNEL);
+		args->csa_rclists = kcalloc(args->csa_nrclists,
+					    sizeof(*args->csa_rclists),
+					    GFP_KERNEL);
 		if (unlikely(args->csa_rclists == NULL))
 			return htonl(NFS4ERR_RESOURCE);
 
-- 
2.43.0