From: Eric Biggers <ebiggers@xxxxxxxxxx> Subject: fs/filesystems.c: downgrade user-reachable WARN_ONCE() to pr_warn_once() 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(). Keep it printed once only, since the intent of this warning is to detect a bug in modprobe at boot time. Printing the warning more than once wouldn't really provide any useful extra information. Link: http://lkml.kernel.org/r/20200312202552.241885-3-ebiggers@xxxxxxxxxx Fixes: 41124db869b7 ("fs: warn in case userspace lied about modprobe return") Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx> Reviewed-by: Jessica Yu <jeyu@xxxxxxxxxx> Cc: Alexei Starovoitov <ast@xxxxxxxxxx> Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> Cc: Jeff Vander Stoep <jeffv@xxxxxxxxxx> Cc: Jessica Yu <jeyu@xxxxxxxxxx> Cc: Kees Cook <keescook@xxxxxxxxxxxx> Cc: Luis Chamberlain <mcgrof@xxxxxxxxxx> Cc: NeilBrown <neilb@xxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> [4.13+] Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- fs/filesystems.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) --- a/fs/filesystems.c~fs-filesystemsc-downgrade-user-reachable-warn_once-to-pr_warn_once +++ a/fs/filesystems.c @@ -272,7 +272,9 @@ struct file_system_type *get_fs_type(con 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)) { _
