Messages in this thread | | | Date | Mon, 24 Oct 2022 19:56:05 +0200 | Subject | Re: [PATCH v4] skbuff: Proactively round up to kmalloc bucket size | From | Vlastimil Babka <> |
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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@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 > Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> > Cc: Nick Desaulniers <ndesaulniers@google.com> > Cc: David Rientjes <rientjes@google.com> > Cc: Vlastimil Babka <vbabka@suse.cz> > Signed-off-by: Kees Cook <keescook@chromium.org>
Acked-by: Vlastimil Babka <vbabka@suse.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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