[PATCH v3 2/5] fs/filesystems.c: downgrade user-reachable WARN_ONCE() to pr_warn_once()

Eric Biggers
2020-03-15T02:25:05Z

From: Eric Biggers <ebiggers@google.com>

After request_module(), nothing is stopping the module from being
unloaded until someone takes a reference to it via try_get_module().

The WARN_ONCE() in get_fs_type() is thus user-reachable, via userspace
running 'rmmod' concurrently.

Since WARN_ONCE() is for kernel bugs only, not for user-reachable
situations, downgrade this warning to pr_warn_once().

Acked-by: Luis Chamberlain <mcgrof@kernel.org>
Cc: stable@vger.kernel.org
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jeff Vander Stoep <jeffv@google.com>
Cc: Jessica Yu <jeyu@kernel.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: NeilBrown <neilb@suse.com>
Signed-off-by: Eric Biggers <ebiggers@google.com>
---
fs/filesystems.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/fs/filesystems.c b/fs/filesystems.c
index 77bf5f95362da..90b8d879fbaf3 100644
--- a/fs/filesystems.c
+++ b/fs/filesystems.c
@@ -272,7 +272,9 @@ struct file_system_type *get_fs_type(const char *name)
fs = __get_fs_type(name, len);
if (!fs && (request_module("fs-%.*s", len, name) == 0)) {
fs = __get_fs_type(name, len);
- WARN_ONCE(!fs, "request_module fs-%.*s succeeded, but still no fs?\n", len, name);
+ if (!fs)
+ pr_warn_once("request_module fs-%.*s succeeded, but still no fs?\n",
+ len, name);
}

if (dot && fs && !(fs->fs_flags & FS_HAS_SUBTYPE)) {
--
2.25.1