wifi: iwlwifi: pcie: Fix TSO preparation

The allocation of the scatter gather data structure should be done
based on the number of memory chunks that need to be mapped, and it
is not dependent on the overall payload length. Fix it.

In addition, as the skb_to_sgvec() function returns an 'int' do not
assign it to an 'unsigned int' as otherwise the error check would be
useless.

Fixes: 7f5e303 ("wifi: iwlwifi: map entire SKB when sending AMSDUs")
Signed-off-by: Ilan Peer <[email protected]>
Signed-off-by: Miri Korenblit <[email protected]>
Link: https://patch.msgid.link/20250306122425.8c0e23a3d583.I3cb4d6768c9d28ce3da6cd0a6c65466176cfc1ee@changeid
Signed-off-by: Johannes Berg <[email protected]>

Author: ilanpeer2

drivers/net/wireless/intel/iwlwifi/pcie/tx.c

@@ -1869,12 +1869,12 @@ struct sg_table *iwl_pcie_prep_tso(struct iwl_trans *trans, struct sk_buff *skb,
 				   unsigned int offset)
 {
 	struct sg_table *sgt;
-	unsigned int n_segments;
+	unsigned int n_segments = skb_shinfo(skb)->nr_frags + 1;
+	int orig_nents;
 
 	if (WARN_ON_ONCE(skb_has_frag_list(skb)))
 		return NULL;
 
-	n_segments = DIV_ROUND_UP(skb->len - offset, skb_shinfo(skb)->gso_size);
 	*hdr = iwl_pcie_get_page_hdr(trans,
 				     hdr_room + __alignof__(struct sg_table) +
 				     sizeof(struct sg_table) +
@@ -1889,11 +1889,12 @@ struct sg_table *iwl_pcie_prep_tso(struct iwl_trans *trans, struct sk_buff *skb,
 	sg_init_table(sgt->sgl, n_segments);
 
 	/* Only map the data, not the header (it is copied to the TSO page) */
-	sgt->orig_nents = skb_to_sgvec(skb, sgt->sgl, offset,
-				       skb->len - offset);
-	if (WARN_ON_ONCE(sgt->orig_nents <= 0))
+	orig_nents = skb_to_sgvec(skb, sgt->sgl, offset, skb->len - offset);
+	if (WARN_ON_ONCE(orig_nents <= 0))
 		return NULL;
 
+	sgt->orig_nents = orig_nents;
+
 	/* And map the entire SKB */
 	if (dma_map_sgtable(trans->dev, sgt, DMA_TO_DEVICE, 0) < 0)
 		return NULL;