udp: fix skb_copy_and_csum_datagram with odd segment sizes

When iteratively computing a checksum with csum_block_add, track the
offset "pos" to correctly rotate in csum_block_add when offset is odd.

The open coded implementation of skb_copy_and_csum_datagram did this.
With the switch to __skb_datagram_iter calling csum_and_copy_to_iter,
pos was reinitialized to 0 on each call.

Bring back the pos by passing it along with the csum to the callback.

Changes v1->v2
  - pass csum value, instead of csump pointer (Alexander Duyck)

Link: https://lore.kernel.org/netdev/20210128152353.GB27281@optiplex/
Fixes: 950fcaecd5cc ("datagram: consolidate datagram copy to iter helpers")
Reported-by: Oliver Graute <oliver.graute@gmail.com>
Signed-off-by: Willem de Bruijn <willemb@google.com>
Reviewed-by: Alexander Duyck <alexanderduyck@fb.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/r/20210203192952.1849843-1-willemdebruijn.kernel@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/include/linux/uio.h b/include/linux/uio.h
index 72d88566694ee975e6ad69fbae8730e125e0dd56..27ff8eb786dc34817ac875f780b478c2b93a758f 100644 (file)
--- a/include/linux/uio.h
+++ b/include/linux/uio.h
@@ -260,7 +260,13 @@ static inline void iov_iter_reexpand(struct iov_iter *i, size_t count)
 {
        i->count = count;
 }
-size_t csum_and_copy_to_iter(const void *addr, size_t bytes, void *csump, struct iov_iter *i);
+
+struct csum_state {
+       __wsum csum;
+       size_t off;
+};
+
+size_t csum_and_copy_to_iter(const void *addr, size_t bytes, void *csstate, struct iov_iter *i);
 size_t csum_and_copy_from_iter(void *addr, size_t bytes, __wsum *csum, struct iov_iter *i);
 bool csum_and_copy_from_iter_full(void *addr, size_t bytes, __wsum *csum, struct iov_iter *i);
 size_t hash_and_copy_to_iter(const void *addr, size_t bytes, void *hashp,

diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index a21e6a5792c5a53fcdb3ffd29328d9d5f6d5afad..f0b2ccb1bb0182694733683501b55dc4d7dc2bb2 100644 (file)
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -592,14 +592,15 @@ static __wsum csum_and_memcpy(void *to, const void *from, size_t len,
 }
 
 static size_t csum_and_copy_to_pipe_iter(const void *addr, size_t bytes,
-                               __wsum *csum, struct iov_iter *i)
+                                        struct csum_state *csstate,
+                                        struct iov_iter *i)
 {
        struct pipe_inode_info *pipe = i->pipe;
        unsigned int p_mask = pipe->ring_size - 1;
+       __wsum sum = csstate->csum;
+       size_t off = csstate->off;
        unsigned int i_head;
        size_t n, r;
-       size_t off = 0;
-       __wsum sum = *csum;
 
        if (!sanity(i))
                return 0;
@@ -621,7 +622,8 @@ static size_t csum_and_copy_to_pipe_iter(const void *addr, size_t bytes,
                i_head++;
        } while (n);
        i->count -= bytes;
-       *csum = sum;
+       csstate->csum = sum;
+       csstate->off = off;
        return bytes;
 }
 
@@ -1522,18 +1524,19 @@ bool csum_and_copy_from_iter_full(void *addr, size_t bytes, __wsum *csum,
 }
 EXPORT_SYMBOL(csum_and_copy_from_iter_full);
 
-size_t csum_and_copy_to_iter(const void *addr, size_t bytes, void *csump,
+size_t csum_and_copy_to_iter(const void *addr, size_t bytes, void *_csstate,
                             struct iov_iter *i)
 {
+       struct csum_state *csstate = _csstate;
        const char *from = addr;
-       __wsum *csum = csump;
        __wsum sum, next;
-       size_t off = 0;
+       size_t off;
 
        if (unlikely(iov_iter_is_pipe(i)))
-               return csum_and_copy_to_pipe_iter(addr, bytes, csum, i);
+               return csum_and_copy_to_pipe_iter(addr, bytes, _csstate, i);
 
-       sum = *csum;
+       sum = csstate->csum;
+       off = csstate->off;
        if (unlikely(iov_iter_is_discard(i))) {
                WARN_ON(1);     /* for now */
                return 0;
@@ -1561,7 +1564,8 @@ size_t csum_and_copy_to_iter(const void *addr, size_t bytes, void *csump,
                off += v.iov_len;
        })
        )
-       *csum = sum;
+       csstate->csum = sum;
+       csstate->off = off;
        return bytes;
 }
 EXPORT_SYMBOL(csum_and_copy_to_iter);

diff --git a/net/core/datagram.c b/net/core/datagram.c
index 81809fa735a78000b88b60b860615267a94b6497..15ab9ffb27fe999c9038d67d822de715d1e61baa 100644 (file)
--- a/net/core/datagram.c
+++ b/net/core/datagram.c
@@ -721,8 +721,16 @@ static int skb_copy_and_csum_datagram(const struct sk_buff *skb, int offset,
                                      struct iov_iter *to, int len,
                                      __wsum *csump)
 {
-       return __skb_datagram_iter(skb, offset, to, len, true,
-                       csum_and_copy_to_iter, csump);
+       struct csum_state csdata = { .csum = *csump };
+       int ret;
+
+       ret = __skb_datagram_iter(skb, offset, to, len, true,
+                                 csum_and_copy_to_iter, &csdata);
+       if (ret)
+               return ret;
+
+       *csump = csdata.csum;
+       return 0;
 }
 
 /**