added to cifs-2.6.git for-next and added RB and tested-by
On Wed, Jun 25, 2025 at 10:55 AM Stefan Metzmacher <metze@xxxxxxxxx> wrote:
>
> reviewed-by and tested-by: Stefan Metzmacher <metze@xxxxxxxxx>
>
> Am 25.06.25 um 16:46 schrieb David Howells:
> >
> > The handling of received data in the smbdirect client code involves using
> > copy_to_iter() to copy data from the smbd_reponse struct's packet trailer
> > to a folioq buffer provided by netfslib that encapsulates a chunk of
> > pagecache.
> >
> > If, however, CONFIG_HARDENED_USERCOPY=y, this will result in the checks
> > then performed in copy_to_iter() oopsing with something like the following:
> >
> > CIFS: Attempting to mount //172.31.9.1/test
> > CIFS: VFS: RDMA transport established
> > usercopy: Kernel memory exposure attempt detected from SLUB object 'smbd_response_0000000091e24ea1' (offset 81, size 63)!
> > ------------[ cut here ]------------
> > kernel BUG at mm/usercopy.c:102!
> > ...
> > RIP: 0010:usercopy_abort+0x6c/0x80
> > ...
> > Call Trace:
> > <TASK>
> > __check_heap_object+0xe3/0x120
> > __check_object_size+0x4dc/0x6d0
> > smbd_recv+0x77f/0xfe0 [cifs]
> > cifs_readv_from_socket+0x276/0x8f0 [cifs]
> > cifs_read_from_socket+0xcd/0x120 [cifs]
> > cifs_demultiplex_thread+0x7e9/0x2d50 [cifs]
> > kthread+0x396/0x830
> > ret_from_fork+0x2b8/0x3b0
> > ret_from_fork_asm+0x1a/0x30
> >
> > The problem is that the smbd_response slab's packet field isn't marked as
> > being permitted for usercopy.
> >
> > Fix this by passing parameters to kmem_slab_create() to indicate that
> > copy_to_iter() is permitted from the packet region of the smbd_response
> > slab objects, less the header space.
> >
> > Fixes: ee4cdf7ba857 ("netfs: Speed up buffered reading")
> > Reported-by: Stefan Metzmacher <metze@xxxxxxxxx>
> > Link: https://lore.kernel.org/r/acb7f612-df26-4e2a-a35d-7cd040f513e1@xxxxxxxxx/
> > Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
> > cc: Steve French <stfrench@xxxxxxxxxxxxx>
> > cc: Paulo Alcantara <pc@xxxxxxxxxxxxx>
> > cc: linux-cifs@xxxxxxxxxxxxxxx
> > cc: netfs@xxxxxxxxxxxxxxx
> > cc: linux-fsdevel@xxxxxxxxxxxxxxx
> > ---
> > fs/smb/client/smbdirect.c | 18 +++++++++++++-----
> > 1 file changed, 13 insertions(+), 5 deletions(-)
> >
> > diff --git a/fs/smb/client/smbdirect.c b/fs/smb/client/smbdirect.c
> > index ef6bf8d6808d..f9773cc0d562 100644
> > --- a/fs/smb/client/smbdirect.c
> > +++ b/fs/smb/client/smbdirect.c
> > @@ -1475,6 +1475,9 @@ static int allocate_caches_and_workqueue(struct smbd_connection *info)
> > char name[MAX_NAME_LEN];
> > int rc;
> >
> > + if (WARN_ON_ONCE(sp->max_recv_size < sizeof(struct smbdirect_data_transfer)))
> > + return -ENOMEM;
> > +
> > scnprintf(name, MAX_NAME_LEN, "smbd_request_%p", info);
> > info->request_cache =
> > kmem_cache_create(
> > @@ -1492,12 +1495,17 @@ static int allocate_caches_and_workqueue(struct smbd_connection *info)
> > goto out1;
> >
> > scnprintf(name, MAX_NAME_LEN, "smbd_response_%p", info);
> > +
> > + struct kmem_cache_args response_args = {
> > + .align = __alignof__(struct smbd_response),
> > + .useroffset = (offsetof(struct smbd_response, packet) +
> > + sizeof(struct smbdirect_data_transfer)),
> > + .usersize = sp->max_recv_size - sizeof(struct smbdirect_data_transfer),
> > + };
> > info->response_cache =
> > - kmem_cache_create(
> > - name,
> > - sizeof(struct smbd_response) +
> > - sp->max_recv_size,
> > - 0, SLAB_HWCACHE_ALIGN, NULL);
> > + kmem_cache_create(name,
> > + sizeof(struct smbd_response) + sp->max_recv_size,
> > + &response_args, SLAB_HWCACHE_ALIGN);
> > if (!info->response_cache)
> > goto out2;
> >
>
>
--
Thanks,
Steve
