net: Define usercopy region in struct proto slab cache
In support of usercopy hardening, this patch defines a region in the struct proto slab cache in which userspace copy operations are allowed. Some protocols need to copy objects to/from userspace, and they can declare the region via their proto structure with the new usersize and useroffset fields. Initially, if no region is specified (usersize == 0), the entire field is marked as whitelisted. This allows protocols to be whitelisted in subsequent patches. Once all protocols have been annotated, the full-whitelist default can be removed. This region is known as the slab cache's usercopy region. Slab caches can now check that each dynamically sized copy operation involving cache-managed memory falls entirely within the slab's usercopy region. This patch is modified from Brad Spengler/PaX Team's PAX_USERCOPY whitelisting code in the last public patch of grsecurity/PaX based on my understanding of the code. Changes or omissions from the original code are mine and don't reflect the original grsecurity/PaX code. Signed-off-by: David Windsor <dave@nullcore.net> [kees: adjust commit log, split off per-proto patches] [kees: add logic for by-default full-whitelist] Cc: "David S. Miller" <davem@davemloft.net> Cc: Eric Dumazet <edumazet@google.com> Cc: Paolo Abeni <pabeni@redhat.com> Cc: David Howells <dhowells@redhat.com> Cc: netdev@vger.kernel.org Signed-off-by: Kees Cook <keescook@chromium.org>
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@ -1112,6 +1112,8 @@ struct proto {
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struct kmem_cache *slab;
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struct kmem_cache *slab;
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unsigned int obj_size;
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unsigned int obj_size;
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slab_flags_t slab_flags;
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slab_flags_t slab_flags;
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size_t useroffset; /* Usercopy region offset */
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size_t usersize; /* Usercopy region size */
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struct percpu_counter *orphan_count;
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struct percpu_counter *orphan_count;
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@ -3151,8 +3151,12 @@ static int req_prot_init(const struct proto *prot)
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int proto_register(struct proto *prot, int alloc_slab)
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int proto_register(struct proto *prot, int alloc_slab)
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{
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{
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if (alloc_slab) {
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if (alloc_slab) {
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prot->slab = kmem_cache_create(prot->name, prot->obj_size, 0,
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prot->slab = kmem_cache_create_usercopy(prot->name,
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prot->obj_size, 0,
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SLAB_HWCACHE_ALIGN | prot->slab_flags,
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SLAB_HWCACHE_ALIGN | prot->slab_flags,
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prot->usersize ? prot->useroffset : 0,
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prot->usersize ? prot->usersize
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: prot->obj_size,
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NULL);
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NULL);
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if (prot->slab == NULL) {
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if (prot->slab == NULL) {
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