| Message ID | 20210514215209.GA33310@embeddedor (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [next] ceph: Replace zero-length array with flexible array member | expand |
On Fri, May 14, 2021 at 11:51 PM Gustavo A. R. Silva <gustavoars@kernel.org> wrote: > > There is a regular need in the kernel to provide a way to declare > having a dynamically sized set of trailing elements in a structure. > Kernel code should always use “flexible array members”[1] for these > cases. The older style of one-element or zero-length arrays should > no longer be used[2]. > > Notice that, in this case, sizeof(au->reply_buf) translates to zero, > becase in the original code reply_buf is a zero-length array. Now that > reply_buf is transformed into a flexible array, the mentioned line of > code is now replaced by a literal 0. > > Also, as a safeguard, explicitly assign NULL to > auth->authorizer_reply_buf, as no heap is allocated for it, therefore > it should not be accessible. > > [1] https://en.wikipedia.org/wiki/Flexible_array_member > [2] https://www.kernel.org/doc/html/v5.10/process/deprecated.html#zero-length-and-one-element-arrays > > Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org> > --- > net/ceph/auth_none.c | 4 ++-- > net/ceph/auth_none.h | 2 +- > 2 files changed, 3 insertions(+), 3 deletions(-) > > diff --git a/net/ceph/auth_none.c b/net/ceph/auth_none.c > index 70e86e462250..10ee16d2cbf0 100644 > --- a/net/ceph/auth_none.c > +++ b/net/ceph/auth_none.c > @@ -111,8 +111,8 @@ static int ceph_auth_none_create_authorizer( > auth->authorizer = (struct ceph_authorizer *) au; > auth->authorizer_buf = au->buf; > auth->authorizer_buf_len = au->buf_len; > - auth->authorizer_reply_buf = au->reply_buf; > - auth->authorizer_reply_buf_len = sizeof (au->reply_buf); > + auth->authorizer_reply_buf_len = 0; > + auth->authorizer_reply_buf = NULL; > > return 0; > } > diff --git a/net/ceph/auth_none.h b/net/ceph/auth_none.h > index 4158f064302e..3c68c0ee3dab 100644 > --- a/net/ceph/auth_none.h > +++ b/net/ceph/auth_none.h > @@ -16,7 +16,7 @@ struct ceph_none_authorizer { > struct ceph_authorizer base; > char buf[128]; > int buf_len; > - char reply_buf[0]; > + char reply_buf[]; > }; > > struct ceph_auth_none_info { Hi Gustavo, I went ahead and removed reply_buf. We never receive authorizer replies in auth_none mode, so patching it to be a flexible array is rather pointless. Thanks, Ilya
On 5/15/21 05:42, Ilya Dryomov wrote: > > Hi Gustavo, > > I went ahead and removed reply_buf. We never receive authorizer > replies in auth_none mode, so patching it to be a flexible array > is rather pointless. Sounds great. :) Thanks, Ilya. -- Gustavo
diff --git a/net/ceph/auth_none.c b/net/ceph/auth_none.c index 70e86e462250..10ee16d2cbf0 100644 --- a/net/ceph/auth_none.c +++ b/net/ceph/auth_none.c @@ -111,8 +111,8 @@ static int ceph_auth_none_create_authorizer( auth->authorizer = (struct ceph_authorizer *) au; auth->authorizer_buf = au->buf; auth->authorizer_buf_len = au->buf_len; - auth->authorizer_reply_buf = au->reply_buf; - auth->authorizer_reply_buf_len = sizeof (au->reply_buf); + auth->authorizer_reply_buf_len = 0; + auth->authorizer_reply_buf = NULL; return 0; } diff --git a/net/ceph/auth_none.h b/net/ceph/auth_none.h index 4158f064302e..3c68c0ee3dab 100644 --- a/net/ceph/auth_none.h +++ b/net/ceph/auth_none.h @@ -16,7 +16,7 @@ struct ceph_none_authorizer { struct ceph_authorizer base; char buf[128]; int buf_len; - char reply_buf[0]; + char reply_buf[]; }; struct ceph_auth_none_info {
There is a regular need in the kernel to provide a way to declare having a dynamically sized set of trailing elements in a structure. Kernel code should always use “flexible array members”[1] for these cases. The older style of one-element or zero-length arrays should no longer be used[2]. Notice that, in this case, sizeof(au->reply_buf) translates to zero, becase in the original code reply_buf is a zero-length array. Now that reply_buf is transformed into a flexible array, the mentioned line of code is now replaced by a literal 0. Also, as a safeguard, explicitly assign NULL to auth->authorizer_reply_buf, as no heap is allocated for it, therefore it should not be accessible. [1] https://en.wikipedia.org/wiki/Flexible_array_member [2] https://www.kernel.org/doc/html/v5.10/process/deprecated.html#zero-length-and-one-element-arrays Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org> --- net/ceph/auth_none.c | 4 ++-- net/ceph/auth_none.h | 2 +- 2 files changed, 3 insertions(+), 3 deletions(-)