On Wed, Mar 18, 2020 at 04:43:15PM +0100, Jessica Yu wrote:
+++ Eric Biggers [14/03/20 14:34 -0700]:
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);Hm, what was the rationale for warning only once again? It might be useful for debugging issues to see each instance of request_module() failure (and with which fs). However, I don't have a concrete use case to support this argument, so:
Reviewed-by: Jessica Yu jeyu@kernel.org
This was discussed on v2, see https://lkml.kernel.org/lkml/20200313010053.GS11244@42.do-not-panic.com/. If the warning triggers, then it indicates a broken modprobe program. Printing the warning multiple times wouldn't really add any new information.
And in any case, it's printed once both before and after this patch.
- Eric