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Commit d4b3709c authored by Eric Biggers's avatar Eric Biggers Committed by Greg Kroah-Hartman
Browse files

fs/filesystems.c: downgrade user-reachable WARN_ONCE() to pr_warn_once() 



commit 26c5d78c976ca298e59a56f6101a97b618ba3539 upstream.

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.

Fixes: 41124db8 ("fs: warn in case userspace lied about modprobe return")
Signed-off-by: default avatarEric Biggers <ebiggers@google.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Reviewed-by: default avatarJessica Yu <jeyu@kernel.org>
Cc: Alexei Starovoitov <ast@kernel.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: Luis Chamberlain <mcgrof@kernel.org>
Cc: NeilBrown <neilb@suse.com>
Cc: <stable@vger.kernel.org>		[4.13+]
Link: http://lkml.kernel.org/r/20200312202552.241885-3-ebiggers@kernel.org


Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 803ef6fa

fs/filesystems.c

+3 −1
Original line number Diff line number Diff line
@@ -267,7 +267,9 @@ 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)) {