[PATCH 5.10 088/104] udp: fix skb_copy_and_csum_datagram with odd segment sizes

Greg Kroah-Hartman
2021-02-15T15:42:38Z

From: Willem de Bruijn <willemb@google.com>

commit 52cbd23a119c6ebf40a527e53f3402d2ea38eccb upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
include/linux/uio.h | 8 +++++++-
lib/iov_iter.c | 24 ++++++++++++++----------
net/core/datagram.c | 12 ++++++++++--
3 files changed, 31 insertions(+), 13 deletions(-)

--- a/include/linux/uio.h
+++ b/include/linux/uio.h
@@ -260,7 +260,13 @@ static inline void iov_iter_reexpand(str
{
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,
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -592,14 +592,15 @@ static __wsum csum_and_memcpy(void *to,
}

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
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 *
}
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
off += v.iov_len;
})
)
- *csum = sum;
+ csstate->csum = sum;
+ csstate->off = off;
return bytes;
}
EXPORT_SYMBOL(csum_and_copy_to_iter);
--- a/net/core/datagram.c
+++ b/net/core/datagram.c
@@ -721,8 +721,16 @@ static int skb_copy_and_csum_datagram(co
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;
}

/**