From: Eric Biggers <[email protected]>
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().
Cc: [email protected]
Cc: Alexei Starovoitov <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Greg Kroah-Hartman <[email protected]>
Cc: Jeff Vander Stoep <[email protected]>
Cc: Jessica Yu <[email protected]>
Cc: Kees Cook <[email protected]>
Cc: Luis Chamberlain <[email protected]>
Cc: NeilBrown <[email protected]>
Signed-off-by: Eric Biggers <[email protected]>
---
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
On Thu, Mar 12 2020, Eric Biggers wrote:
> From: Eric Biggers <[email protected]>
>
> 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().
>
> Cc: [email protected]
> Cc: Alexei Starovoitov <[email protected]>
> Cc: Andrew Morton <[email protected]>
> Cc: Greg Kroah-Hartman <[email protected]>
> Cc: Jeff Vander Stoep <[email protected]>
> Cc: Jessica Yu <[email protected]>
> Cc: Kees Cook <[email protected]>
> Cc: Luis Chamberlain <[email protected]>
> Cc: NeilBrown <[email protected]>
> Signed-off-by: Eric Biggers <[email protected]>
> ---
> 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);
I strongly support the replacement of "WARN" by "pr_warn".
I wonder if we really want the "once" now. Possibly using rate_limited
would be justified, but I think that in general we should see a warning
every time this event happens.
Thanks,
NeilBrown
> }
>
> if (dot && fs && !(fs->fs_flags & FS_HAS_SUBTYPE)) {
> --
> 2.25.1
On Thu, Mar 12, 2020 at 01:25:50PM -0700, Eric Biggers wrote:
> From: Eric Biggers <[email protected]>
>
> 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().
>
> Cc: [email protected]
> Cc: Alexei Starovoitov <[email protected]>
> Cc: Andrew Morton <[email protected]>
> Cc: Greg Kroah-Hartman <[email protected]>
> Cc: Jeff Vander Stoep <[email protected]>
> Cc: Jessica Yu <[email protected]>
> Cc: Kees Cook <[email protected]>
> Cc: Luis Chamberlain <[email protected]>
> Cc: NeilBrown <[email protected]>
> Signed-off-by: Eric Biggers <[email protected]>
Acked-by: Luis Chamberlain <[email protected]>
Luis
On Fri, Mar 13, 2020 at 09:06:46AM +1100, NeilBrown wrote:
> On Thu, Mar 12 2020, Eric Biggers wrote:
>
> > From: Eric Biggers <[email protected]>
> >
> > 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().
> >
> > Cc: [email protected]
> > Cc: Alexei Starovoitov <[email protected]>
> > Cc: Andrew Morton <[email protected]>
> > Cc: Greg Kroah-Hartman <[email protected]>
> > Cc: Jeff Vander Stoep <[email protected]>
> > Cc: Jessica Yu <[email protected]>
> > Cc: Kees Cook <[email protected]>
> > Cc: Luis Chamberlain <[email protected]>
> > Cc: NeilBrown <[email protected]>
> > Signed-off-by: Eric Biggers <[email protected]>
> > ---
> > 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);
>
> I strongly support the replacement of "WARN" by "pr_warn".
> I wonder if we really want the "once" now. Possibly using rate_limited
> would be justified, but I think that in general we should see a warning
> every time this event happens.
Since the usefulness of the print is at boot, I think pr_warn_once() is
good right now but just because I cannot think of a case where multiple
prints are currently desirable, or where this should be possible
post-boot. Can you?
Luis