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Message-ID: <f8d72aa1-3f64-b1a1-b776-f8c181f09ca4@suse.cz> Date: Mon, 24 Oct 2022 19:56:05 +0200 From: Vlastimil Babka <vbabka@...e.cz> To: Kees Cook <keescook@...omium.org>, "David S. Miller" <davem@...emloft.net> Cc: Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Nick Desaulniers <ndesaulniers@...gle.com>, David Rientjes <rientjes@...gle.com>, Pavel Begunkov <asml.silence@...il.com>, Menglong Dong <imagedong@...cent.com>, linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org Subject: Re: [PATCH v4] skbuff: Proactively round up to kmalloc bucket size On 10/22/22 01:49, Kees Cook wrote: > Instead of discovering the kmalloc bucket size _after_ allocation, round > up proactively so the allocation is explicitly made for the full size, > allowing the compiler to correctly reason about the resulting size of > the buffer through the existing __alloc_size() hint. > > This will allow for kernels built with CONFIG_UBSAN_BOUNDS or the > coming dynamic bounds checking under CONFIG_FORTIFY_SOURCE to gain > back the __alloc_size() hints that were temporarily reverted in commit > 93dd04ab0b2b ("slab: remove __alloc_size attribute from __kmalloc_track_caller") > > Cc: "David S. Miller" <davem@...emloft.net> > Cc: Eric Dumazet <edumazet@...gle.com> > Cc: Jakub Kicinski <kuba@...nel.org> > Cc: Paolo Abeni <pabeni@...hat.com> > Cc: netdev@...r.kernel.org > Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org> > Cc: Nick Desaulniers <ndesaulniers@...gle.com> > Cc: David Rientjes <rientjes@...gle.com> > Cc: Vlastimil Babka <vbabka@...e.cz> > Signed-off-by: Kees Cook <keescook@...omium.org> Acked-by: Vlastimil Babka <vbabka@...e.cz> Nit below: > --- > v4: use kmalloc_size_roundup() in callers, not kmalloc_reserve() > v3: https://lore.kernel.org/lkml/20221018093005.give.246-kees@kernel.org > v2: https://lore.kernel.org/lkml/20220923202822.2667581-4-keescook@chromium.org > --- > net/core/skbuff.c | 50 +++++++++++++++++++++++------------------------ > 1 file changed, 25 insertions(+), 25 deletions(-) > > diff --git a/net/core/skbuff.c b/net/core/skbuff.c > index 651a82d30b09..77af430296e2 100644 > --- a/net/core/skbuff.c > +++ b/net/core/skbuff.c > @@ -508,14 +508,14 @@ struct sk_buff *__alloc_skb(unsigned int size, gfp_t gfp_mask, > */ > size = SKB_DATA_ALIGN(size); > size += SKB_DATA_ALIGN(sizeof(struct skb_shared_info)); > - data = kmalloc_reserve(size, gfp_mask, node, &pfmemalloc); > + osize = kmalloc_size_roundup(size); > + data = kmalloc_reserve(osize, gfp_mask, node, &pfmemalloc); > if (unlikely(!data)) > goto nodata; > /* kmalloc(size) might give us more room than requested. The line above should now say kmalloc_size_roundup(size), or maybe could be deleted completely now? > * Put skb_shared_info exactly at the end of allocated zone, > * to allow max possible filling before reallocation. > */ > - osize = ksize(data); > size = SKB_WITH_OVERHEAD(osize); > prefetchw(data + size); >
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