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 --- net/core/skbuff.c | 34 ++++++++++++++++++---------------- 1 file changed, 18 insertions(+), 16 deletions(-)
diff --git a/net/core/skbuff.c b/net/core/skbuff.c index 974bbbbe7138..4fe4c7544c1d 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -427,14 +427,15 @@ 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); - if (unlikely(!data)) - goto nodata; - /* kmalloc(size) might give us more room than requested. + /* kmalloc(size) might give us more room than requested, so + * allocate the true bucket size up front. * Put skb_shared_info exactly at the end of allocated zone, * to allow max possible filling before reallocation. */ - osize = ksize(data); + osize = kmalloc_size_roundup(size); + data = kmalloc_reserve(osize, gfp_mask, node, &pfmemalloc); + if (unlikely(!data)) + goto nodata; size = SKB_WITH_OVERHEAD(osize); prefetchw(data + size);
@@ -1709,6 +1710,7 @@ int pskb_expand_head(struct sk_buff *skb, int nhead, int ntail, { int i, osize = skb_end_offset(skb); int size = osize + nhead + ntail; + int alloc_size; long off; u8 *data;
@@ -1722,11 +1724,11 @@ int pskb_expand_head(struct sk_buff *skb, int nhead, int ntail,
if (skb_pfmemalloc(skb)) gfp_mask |= __GFP_MEMALLOC; - data = kmalloc_reserve(size + SKB_DATA_ALIGN(sizeof(struct skb_shared_info)), - gfp_mask, NUMA_NO_NODE, NULL); + alloc_size = kmalloc_size_roundup(size + SKB_DATA_ALIGN(sizeof(struct skb_shared_info))); + data = kmalloc_reserve(alloc_size, gfp_mask, NUMA_NO_NODE, NULL); if (!data) goto nodata; - size = SKB_WITH_OVERHEAD(ksize(data)); + size = SKB_WITH_OVERHEAD(alloc_size);
/* Copy only real data... and, alas, header. This should be * optimized for the cases when header is void. @@ -6063,19 +6065,19 @@ static int pskb_carve_inside_header(struct sk_buff *skb, const u32 off, int i; int size = skb_end_offset(skb); int new_hlen = headlen - off; + int alloc_size; u8 *data;
size = SKB_DATA_ALIGN(size);
if (skb_pfmemalloc(skb)) gfp_mask |= __GFP_MEMALLOC; - data = kmalloc_reserve(size + - SKB_DATA_ALIGN(sizeof(struct skb_shared_info)), - gfp_mask, NUMA_NO_NODE, NULL); + alloc_size = kmalloc_size_roundup(size + SKB_DATA_ALIGN(sizeof(struct skb_shared_info))); + data = kmalloc_reserve(alloc_size, gfp_mask, NUMA_NO_NODE, NULL); if (!data) return -ENOMEM;
- size = SKB_WITH_OVERHEAD(ksize(data)); + size = SKB_WITH_OVERHEAD(alloc_size);
/* Copy real data, and all frags */ skb_copy_from_linear_data_offset(skb, off, data, new_hlen); @@ -6184,18 +6186,18 @@ static int pskb_carve_inside_nonlinear(struct sk_buff *skb, const u32 off, u8 *data; const int nfrags = skb_shinfo(skb)->nr_frags; struct skb_shared_info *shinfo; + int alloc_size;
size = SKB_DATA_ALIGN(size);
if (skb_pfmemalloc(skb)) gfp_mask |= __GFP_MEMALLOC; - data = kmalloc_reserve(size + - SKB_DATA_ALIGN(sizeof(struct skb_shared_info)), - gfp_mask, NUMA_NO_NODE, NULL); + alloc_size = kmalloc_size_roundup(size + SKB_DATA_ALIGN(sizeof(struct skb_shared_info))); + data = kmalloc_reserve(alloc_size, gfp_mask, NUMA_NO_NODE, NULL); if (!data) return -ENOMEM;
- size = SKB_WITH_OVERHEAD(ksize(data)); + size = SKB_WITH_OVERHEAD(alloc_size);
memcpy((struct skb_shared_info *)(data + size), skb_shinfo(skb), offsetof(struct skb_shared_info, frags[0]));