| Message ID | 20220923202822.2667581-5-keescook@chromium.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | slab: Introduce kmalloc_size_roundup() | expand |
On Fri, 2022-09-23 at 13:28 -0700, Kees Cook wrote: > All callers of APIs that allowed a 0-sized frag_size appear to be > passing actual size information already AFAICS, not yet: drivers/net/ethernet/qlogic/qed/qed_ll2.c: skb = build_skb(buffer->data, 0); // -> __build_skb(..., 0) // -> __build_skb_around() drivers/net/ethernet/broadcom/bnx2.c: skb = build_skb(data, 0); I guess some more drivers have calls leading to __build_skb_around(..., 0) there are several call path to checks... > , so this use of ksize() can > be removed. However, just in case there is something still depending > on this behavior, issue a WARN and fall back to as before to ksize() > which means we'll also potentially get KASAN warnings. > > Cc: "David S. Miller" <davem@davemloft.net> > Cc: Eric Dumazet <edumazet@google.com> > Cc: Jakub Kicinski <kuba@kernel.org> > Cc: Paolo Abeni <pabeni@redhat.com> > Cc: netdev@vger.kernel.org > Signed-off-by: Kees Cook <keescook@chromium.org> > --- > net/core/skbuff.c | 18 ++++++++++-------- > 1 file changed, 10 insertions(+), 8 deletions(-) > > diff --git a/net/core/skbuff.c b/net/core/skbuff.c > index 0b30fbdbd0d0..84ca89c781cd 100644 > --- a/net/core/skbuff.c > +++ b/net/core/skbuff.c > @@ -195,7 +195,11 @@ static void __build_skb_around(struct sk_buff *skb, void *data, > unsigned int frag_size) > { > struct skb_shared_info *shinfo; > - unsigned int size = frag_size ? : ksize(data); > + unsigned int size = frag_size; > + > + /* All callers should be setting frag size now? */ > + if (WARN_ON_ONCE(size == 0)) > + size = ksize(data); At some point in the future, I guess we could even drop this check, right? Thanks! Paolo
On Sun, Sep 25, 2022 at 09:17:40AM +0200, Paolo Abeni wrote: > On Fri, 2022-09-23 at 13:28 -0700, Kees Cook wrote: > > All callers of APIs that allowed a 0-sized frag_size appear to be > > passing actual size information already > > AFAICS, not yet: > > drivers/net/ethernet/qlogic/qed/qed_ll2.c: > skb = build_skb(buffer->data, 0); // -> __build_skb(..., 0) > // -> __build_skb_around() > > drivers/net/ethernet/broadcom/bnx2.c: > skb = build_skb(data, 0); > > I guess some more drivers have calls leading to > > __build_skb_around(..., 0) > > there are several call path to checks... Ah-ha! Thank you. I will try to hunt these down -- I think we can't remove the "secret resizing" effect of ksize() without fixing these. > > [...] > > diff --git a/net/core/skbuff.c b/net/core/skbuff.c > > index 0b30fbdbd0d0..84ca89c781cd 100644 > > --- a/net/core/skbuff.c > > +++ b/net/core/skbuff.c > > @@ -195,7 +195,11 @@ static void __build_skb_around(struct sk_buff *skb, void *data, > > unsigned int frag_size) > > { > > struct skb_shared_info *shinfo; > > - unsigned int size = frag_size ? : ksize(data); > > + unsigned int size = frag_size; > > + > > + /* All callers should be setting frag size now? */ > > + if (WARN_ON_ONCE(size == 0)) > > + size = ksize(data); > > At some point in the future, I guess we could even drop this check, > right? Alternatively, we might be able to ask the slab if "data" came from kmalloc or a kmem_cache, and if the former, do: data = krealloc(kmalloc_size_roundup(ksize(data), ...) But that seems ugly...
diff --git a/net/core/skbuff.c b/net/core/skbuff.c index 0b30fbdbd0d0..84ca89c781cd 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -195,7 +195,11 @@ static void __build_skb_around(struct sk_buff *skb, void *data, unsigned int frag_size) { struct skb_shared_info *shinfo; - unsigned int size = frag_size ? : ksize(data); + unsigned int size = frag_size; + + /* All callers should be setting frag size now? */ + if (WARN_ON_ONCE(size == 0)) + size = ksize(data); size -= SKB_DATA_ALIGN(sizeof(struct skb_shared_info)); @@ -220,12 +224,10 @@ static void __build_skb_around(struct sk_buff *skb, void *data, /** * __build_skb - build a network buffer * @data: data buffer provided by caller - * @frag_size: size of data, or 0 if head was kmalloced + * @frag_size: size of data * * Allocate a new &sk_buff. Caller provides space holding head and - * skb_shared_info. @data must have been allocated by kmalloc() only if - * @frag_size is 0, otherwise data should come from the page allocator - * or vmalloc() + * skb_shared_info. * The return is the new skb buffer. * On a failure the return is %NULL, and @data is not freed. * Notes : @@ -272,7 +274,7 @@ EXPORT_SYMBOL(build_skb); * build_skb_around - build a network buffer around provided skb * @skb: sk_buff provide by caller, must be memset cleared * @data: data buffer provided by caller - * @frag_size: size of data, or 0 if head was kmalloced + * @frag_size: size of data */ struct sk_buff *build_skb_around(struct sk_buff *skb, void *data, unsigned int frag_size) @@ -294,7 +296,7 @@ EXPORT_SYMBOL(build_skb_around); /** * __napi_build_skb - build a network buffer * @data: data buffer provided by caller - * @frag_size: size of data, or 0 if head was kmalloced + * @frag_size: size of data * * Version of __build_skb() that uses NAPI percpu caches to obtain * skbuff_head instead of inplace allocation. @@ -318,7 +320,7 @@ static struct sk_buff *__napi_build_skb(void *data, unsigned int frag_size) /** * napi_build_skb - build a network buffer * @data: data buffer provided by caller - * @frag_size: size of data, or 0 if head was kmalloced + * @frag_size: size of data * * Version of __napi_build_skb() that takes care of skb->head_frag * and skb->pfmemalloc when the data is a page or page fragment.
All callers of APIs that allowed a 0-sized frag_size appear to be passing actual size information already, so this use of ksize() can be removed. However, just in case there is something still depending on this behavior, issue a WARN and fall back to as before to ksize() which means we'll also potentially get KASAN warnings. Cc: "David S. Miller" <davem@davemloft.net> Cc: Eric Dumazet <edumazet@google.com> Cc: Jakub Kicinski <kuba@kernel.org> Cc: Paolo Abeni <pabeni@redhat.com> Cc: netdev@vger.kernel.org Signed-off-by: Kees Cook <keescook@chromium.org> --- net/core/skbuff.c | 18 ++++++++++-------- 1 file changed, 10 insertions(+), 8 deletions(-)