2020-10-21 14:51:05

by J. Bruce Fields

Subject: [PATCH] NFSv4.2: fix failure to unregister shrinker

From: "J. Bruce Fields" <[email protected]>

We forgot to unregister the nfs4_xattr_large_entry_shrinker.

That leaves the global list of shrinkers corrupted after unload of the
nfs module, after which possibly unrelated code that calls
register_shrinker() or unregister_shrinker() gets a BUG() with
"supervisor write access in kernel mode".

And similarly for the nfs4_xattr_large_entry_lru.

Reported-by: Kris Karas <[email protected]>
Tested-By: Kris Karas <[email protected]>
Signed-off-by: J. Bruce Fields <[email protected]>
---
fs/nfs/nfs42xattr.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/fs/nfs/nfs42xattr.c b/fs/nfs/nfs42xattr.c
index 86777996cfec..55b44a42d625 100644
--- a/fs/nfs/nfs42xattr.c
+++ b/fs/nfs/nfs42xattr.c
@@ -1048,8 +1048,10 @@ int __init nfs4_xattr_cache_init(void)

void nfs4_xattr_cache_exit(void)
{
+ unregister_shrinker(&nfs4_xattr_large_entry_shrinker);
unregister_shrinker(&nfs4_xattr_entry_shrinker);
unregister_shrinker(&nfs4_xattr_cache_shrinker);
+ list_lru_destroy(&nfs4_xattr_large_entry_lru);
list_lru_destroy(&nfs4_xattr_entry_lru);
list_lru_destroy(&nfs4_xattr_cache_lru);
kmem_cache_destroy(nfs4_xattr_cache_cachep);
--
2.26.2

2020-11-12 14:04:15

by J. Bruce Fields

Subject: Re: [PATCH] NFSv4.2: fix failure to unregister shrinker

Looks like this patch got lost, do you need me to resend?

I should also have added a stable cc and a

Fixes: 95ad37f90c33 "NFSv4.2: add client side xattr caching."

--b.

On Wed, Oct 21, 2020 at 10:34:15AM -0400, bfields wrote:
> From: "J. Bruce Fields" <[email protected]>
>
> We forgot to unregister the nfs4_xattr_large_entry_shrinker.
>
> That leaves the global list of shrinkers corrupted after unload of the
> nfs module, after which possibly unrelated code that calls
> register_shrinker() or unregister_shrinker() gets a BUG() with
> "supervisor write access in kernel mode".
>
> And similarly for the nfs4_xattr_large_entry_lru.
>
> Reported-by: Kris Karas <[email protected]>
> Tested-By: Kris Karas <[email protected]>
> Signed-off-by: J. Bruce Fields <[email protected]>
> ---
> fs/nfs/nfs42xattr.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/fs/nfs/nfs42xattr.c b/fs/nfs/nfs42xattr.c
> index 86777996cfec..55b44a42d625 100644
> --- a/fs/nfs/nfs42xattr.c
> +++ b/fs/nfs/nfs42xattr.c
> @@ -1048,8 +1048,10 @@ int __init nfs4_xattr_cache_init(void)
>
> void nfs4_xattr_cache_exit(void)
> {
> + unregister_shrinker(&nfs4_xattr_large_entry_shrinker);
> unregister_shrinker(&nfs4_xattr_entry_shrinker);
> unregister_shrinker(&nfs4_xattr_cache_shrinker);
> + list_lru_destroy(&nfs4_xattr_large_entry_lru);
> list_lru_destroy(&nfs4_xattr_entry_lru);
> list_lru_destroy(&nfs4_xattr_cache_lru);
> kmem_cache_destroy(nfs4_xattr_cache_cachep);
> --
> 2.26.2
>

2020-11-12 14:08:04

by Anna Schumaker

Subject: Re: [PATCH] NFSv4.2: fix failure to unregister shrinker

No need to resend! I'll make sure the fixes & cc line get added to the commit

On Thu, Nov 12, 2020 at 9:03 AM J. Bruce Fields <[email protected]> wrote:
>
> Looks like this patch got lost, do you need me to resend?
>
> I should also have added a stable cc and a
>
> Fixes: 95ad37f90c33 "NFSv4.2: add client side xattr caching."
>
> --b.
>
> On Wed, Oct 21, 2020 at 10:34:15AM -0400, bfields wrote:
> > From: "J. Bruce Fields" <[email protected]>
> >
> > We forgot to unregister the nfs4_xattr_large_entry_shrinker.
> >
> > That leaves the global list of shrinkers corrupted after unload of the
> > nfs module, after which possibly unrelated code that calls
> > register_shrinker() or unregister_shrinker() gets a BUG() with
> > "supervisor write access in kernel mode".
> >
> > And similarly for the nfs4_xattr_large_entry_lru.
> >
> > Reported-by: Kris Karas <[email protected]>
> > Tested-By: Kris Karas <[email protected]>
> > Signed-off-by: J. Bruce Fields <[email protected]>
> > ---
> > fs/nfs/nfs42xattr.c | 2 ++
> > 1 file changed, 2 insertions(+)
> >
> > diff --git a/fs/nfs/nfs42xattr.c b/fs/nfs/nfs42xattr.c
> > index 86777996cfec..55b44a42d625 100644
> > --- a/fs/nfs/nfs42xattr.c
> > +++ b/fs/nfs/nfs42xattr.c
> > @@ -1048,8 +1048,10 @@ int __init nfs4_xattr_cache_init(void)
> >
> > void nfs4_xattr_cache_exit(void)
> > {
> > + unregister_shrinker(&nfs4_xattr_large_entry_shrinker);
> > unregister_shrinker(&nfs4_xattr_entry_shrinker);
> > unregister_shrinker(&nfs4_xattr_cache_shrinker);
> > + list_lru_destroy(&nfs4_xattr_large_entry_lru);
> > list_lru_destroy(&nfs4_xattr_entry_lru);
> > list_lru_destroy(&nfs4_xattr_cache_lru);
> > kmem_cache_destroy(nfs4_xattr_cache_cachep);
> > --
> > 2.26.2
> >