[PATCH 1/6] coredump: don't switch a dumper that has no files table

[Christian Brauner <brauner@kernel.org>]

Tasks without an fdtable are skipped in coredump_close_files(). The
coredump client itself doesn't use the same check. Since
put_files_struct() doesn't tolerate NULL it will oops for such tasks
without an fdtable. The prime suspect for this behavior are vhost
workers. Skip the switch for a coredump client without a table.

Fixes: b2b36bcb13ea ("coredump: add COREDUMP_CLOSE_FILES")
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
---
 fs/coredump.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/fs/coredump.c b/fs/coredump.c
index 1fba3fed1a07..791a9268ed96 100644
--- a/fs/coredump.c
+++ b/fs/coredump.c
@@ -579,7 +579,11 @@ static bool coredump_close_files(struct core_state *core_state)
 	/* Use the dumper's real creds not the overridden ones. */
 	scoped_with_creds(current_real_cred()) {
 		io_uring_task_cancel();
-		switch_files_struct(current, files);
+		/* The dumper itself may be a vhost worker without a table. */
+		if (current->files)
+			switch_files_struct(current, files);
+		else
+			put_files_struct(files);
 	}
 
 	coredump_wait_inactive(core_state);

-- 
2.53.0