From cf616096a0f3a2b60f7d68b6b39674a6867ded9c Mon Sep 17 00:00:00 2001 From: Anna Schumaker Date: Tue, 30 Jun 2026 14:31:00 -0400 Subject: [PATCH 1/2] NFS: Pin the 'struct nfs_server' during a FREE_STATEID call Dan Aloni reports that he was able to hit a use-after-free bug if a FREE_STATEID operation gets delayed for whatever reason. Fix this by bumping the refcount of the 'struct nfs_server' object for the duration of the FREE_STATEID so it doesn't get cleaned up from underneath us while operations are still in flight. Reported-by: Dan Aloni Fixes: 7c1d5fae4a87 ("NFSv4: Convert nfs41_free_stateid to use an asynchronous RPC call") Tested-by: Dan Aloni Signed-off-by: Anna Schumaker --- fs/nfs/nfs4proc.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c index 1360409d8de9..71b6ab863b39 100644 --- a/fs/nfs/nfs4proc.c +++ b/fs/nfs/nfs4proc.c @@ -10364,6 +10364,7 @@ static void nfs41_free_stateid_release(void *calldata) struct nfs_free_stateid_data *data = calldata; struct nfs_client *clp = data->server->nfs_client; + nfs_sb_deactive(data->server->super); nfs_put_client(clp); kfree(calldata); } @@ -10405,6 +10406,10 @@ static int nfs41_free_stateid(struct nfs_server *server, if (!refcount_inc_not_zero(&clp->cl_count)) return -EIO; + if (!nfs_sb_active(server->super)) { + nfs_put_client(clp); + return -EIO; + } nfs4_state_protect(clp, NFS_SP4_MACH_CRED_STATEID, &task_setup.rpc_client, &msg); From 4aeb63d5ac2dba2a474e7b64d60776d9dd1c6cd2 Mon Sep 17 00:00:00 2001 From: Anna Schumaker Date: Tue, 30 Jun 2026 15:39:45 -0400 Subject: [PATCH 2/2] NFS: Decrement refcounts if allocating nfs_free_stateid_data fails I noticed that we were immediately exiting this function if the allocation fails, leaving the client and server object refcounts bumped. Fix this by creating a common exit point to clean up dangling references. Fixes: 576acc259146 ("nfs4: take a reference on the nfs_client when running FREE_STATEID") Signed-off-by: Anna Schumaker --- fs/nfs/nfs4proc.c | 20 +++++++++++++------- 1 file changed, 13 insertions(+), 7 deletions(-) diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c index 71b6ab863b39..7d98e9a98580 100644 --- a/fs/nfs/nfs4proc.c +++ b/fs/nfs/nfs4proc.c @@ -10403,21 +10403,22 @@ static int nfs41_free_stateid(struct nfs_server *server, struct nfs_free_stateid_data *data; struct rpc_task *task; struct nfs_client *clp = server->nfs_client; + int ret = -EIO; if (!refcount_inc_not_zero(&clp->cl_count)) - return -EIO; - if (!nfs_sb_active(server->super)) { - nfs_put_client(clp); - return -EIO; - } + return ret; + if (!nfs_sb_active(server->super)) + goto out_put_clp; nfs4_state_protect(clp, NFS_SP4_MACH_CRED_STATEID, &task_setup.rpc_client, &msg); dprintk("NFS call free_stateid %p\n", stateid); data = kmalloc_obj(*data); - if (!data) - return -ENOMEM; + if (!data) { + ret = -ENOMEM; + goto out_put_server; + } data->server = server; nfs4_stateid_copy(&data->args.stateid, stateid); @@ -10433,6 +10434,11 @@ static int nfs41_free_stateid(struct nfs_server *server, rpc_put_task(task); stateid->type = NFS4_FREED_STATEID_TYPE; return 0; +out_put_server: + nfs_sb_deactive(server->super); +out_put_clp: + nfs_put_client(clp); + return ret; } static void