From: Eric Biggers <ebiggers@xxxxxxxxxx>
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: 41124db869b7 ("fs: warn in case userspace lied about modprobe return")
Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
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+]
Link: http://lkml.kernel.org/r/20200312202552.241885-3-ebiggers@xxxxxxxxxx
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/filesystems.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
--- a/fs/filesystems.c
+++ b/fs/filesystems.c
@@ -271,7 +271,9 @@ 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)) {
