[PATCH 04/10] nfs: Fix oops in nfs_netfs_init_request() when copying to cache

David Howells
2024-12-13T13:50:59Z

When netfslib wants to copy some data that has just been read on behalf of
nfs, it creates a new write request and calls nfs_netfs_init_request() to
initialise it, but with a NULL file pointer. This causes
nfs_file_open_context() to oops - however, we don't actually need the nfs
context as we're only going to write to the cache.

Fix this by just returning if we aren't given a file pointer and emit a
warning if the request was for something other than copy-to-cache.

Further, fix nfs_netfs_free_request() so that it doesn't try to free the
context if the pointer is NULL.

Fixes: ee4cdf7ba857 ("netfs: Speed up buffered reading")
Reported-by: Max Kellermann <max.kellermann@ionos.com>
Closes: https://lore.kernel.org/r/CAKPOu+9DyMbKLhyJb7aMLDTb=Fh0T8Teb9sjuf_pze+XWT1VaQ@mail.gmail.com/
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Trond Myklebust <trondmy@kernel.org>
cc: Anna Schumaker <anna@kernel.org>
cc: Dave Wysochanski <dwysocha@redhat.com>
cc: Jeff Layton <jlayton@kernel.org>
cc: linux-nfs@vger.kernel.org
cc: netfs@lists.linux.dev
cc: linux-fsdevel@vger.kernel.org
---
fs/nfs/fscache.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/fs/nfs/fscache.c b/fs/nfs/fscache.c
index 810269ee0a50..d49e4ce27999 100644
--- a/fs/nfs/fscache.c
+++ b/fs/nfs/fscache.c
@@ -263,6 +263,12 @@ int nfs_netfs_readahead(struct readahead_control *ractl)
static atomic_t nfs_netfs_debug_id;
static int nfs_netfs_init_request(struct netfs_io_request *rreq, struct file *file)
{
+ if (!file) {
+ if (WARN_ON_ONCE(rreq->origin != NETFS_PGPRIV2_COPY_TO_CACHE))
+ return -EIO;
+ return 0;
+ }
+
rreq->netfs_priv = get_nfs_open_context(nfs_file_open_context(file));
rreq->debug_id = atomic_inc_return(&nfs_netfs_debug_id);
/* [DEPRECATED] Use PG_private_2 to mark folio being written to the cache. */
@@ -274,7 +280,8 @@ static int nfs_netfs_init_request(struct netfs_io_request *rreq, struct file *fi

static void nfs_netfs_free_request(struct netfs_io_request *rreq)
{
- put_nfs_open_context(rreq->netfs_priv);
+ if (rreq->netfs_priv)
+ put_nfs_open_context(rreq->netfs_priv);
}

static struct nfs_netfs_io_data *nfs_netfs_alloc(struct netfs_io_subrequest *sreq)