wifi: cfg80211: allow cfg80211_defragment_element() without output

If we just want to determine the length of the fragmented
data, we basically need the same logic, and really we want
it to be _literally_ the same logic, so it cannot be out
of sync in any way.

Allow calling cfg80211_defragment_element() without an output
buffer, where it then just returns the required output size.

Also add this to the tests, just to exercise it, using the
pre-calculated length to really do the defragmentation, which
checks that this is sufficient.

type=feature
ticket=none

Change-Id: Ib441903f4b8644ba04b1c766f90580ee6f54fc66
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Reviewed-on: https://gerritwcs.ir.intel.com/c/iwlwifi-stack-dev/+/94095
tested: iil_jenkins iil_jenkins <EC.GER.UNIX.IIL.JENKINS@INTEL.COM>
automatic-review: iil_jenkins iil_jenkins <EC.GER.UNIX.IIL.JENKINS@INTEL.COM>
Reviewed-by: Miriam Rachel Korenblit <miriam.rachel.korenblit@intel.com>
Reviewed-by: Benjamin Berg <benjamin.berg@intel.com>
x-iwlwifi-stack-dev: eded020a46ffcfc296168a6bcc5d40b41f0d9029

4 files changed, 46 insertions, 17 deletions

diff --git a/include/net/cfg80211.h b/include/net/cfg80211.h
index f8ea18d537..f8a00b8bff 100644
--- a/include/net/cfg80211.h
+++ b/include/net/cfg80211.h
@@ -6889,8 +6889,8 @@ cfg80211_find_vendor_ie(unsigned int oui, int oui_type,
  * @elem: the element to defragment
  * @ies: elements where @elem is contained
  * @ieslen: length of @ies
- * @data: buffer to store element data
- * @data_len: length of @data
+ * @data: buffer to store element data, or %NULL to just determine size
+ * @data_len: length of @data, or 0
  * @frag_id: the element ID of fragments
  *
  * Return: length of @data, or -EINVAL on error
diff --git a/net/wireless/scan.c b/net/wireless/scan.c
index ef968738d8..49591d1ba4 100644
--- a/net/wireless/scan.c
+++ b/net/wireless/scan.c
@@ -2510,16 +2510,22 @@ ssize_t cfg80211_defragment_element(const struct element *elem, const u8 *ies,
 
 	if (elem->id == WLAN_EID_EXTENSION) {
 		copied = elem->datalen - 1;
-		if (copied > data_len)
-			return -ENOSPC;
 
-		memmove(data, elem->data + 1, copied);
+		if (data) {
+			if (copied > data_len)
+				return -ENOSPC;
+
+			memmove(data, elem->data + 1, copied);
+		}
 	} else {
 		copied = elem->datalen;
-		if (copied > data_len)
-			return -ENOSPC;
 
-		memmove(data, elem->data, copied);
+		if (data) {
+			if (copied > data_len)
+				return -ENOSPC;
+
+			memmove(data, elem->data, copied);
+		}
 	}
 
 	/* Fragmented elements must have 255 bytes */
@@ -2538,10 +2544,13 @@ ssize_t cfg80211_defragment_element(const struct element *elem, const u8 *ies,
 
 		elem_datalen = elem->datalen;
 
-		if (copied + elem_datalen > data_len)
-			return -ENOSPC;
+		if (data) {
+			if (copied + elem_datalen > data_len)
+				return -ENOSPC;
+
+			memmove(data + copied, elem->data, elem_datalen);
+		}
 
-		memmove(data + copied, elem->data, elem_datalen);
 		copied += elem_datalen;
 
 		/* Only the last fragment may be short */
diff --git a/net/wireless/tests/fragmentation.c b/net/wireless/tests/fragmentation.c
index 49a339ca88..411fae18cd 100644
--- a/net/wireless/tests/fragmentation.c
+++ b/net/wireless/tests/fragmentation.c
@@ -2,7 +2,7 @@
 /*
  * KUnit tests for element fragmentation
  *
- * Copyright (C) 2023 Intel Corporation
+ * Copyright (C) 2023-2024 Intel Corporation
  */
 #include <linux/ieee80211.h>
 #include <net/cfg80211.h>
@@ -27,7 +27,12 @@ static void defragment_0(struct kunit *test)
 
 	ret = cfg80211_defragment_element((void *)input,
 					  input, sizeof(input),
-					  data, sizeof(input),
+					  NULL, 0,
+					  WLAN_EID_FRAGMENT);
+	KUNIT_EXPECT_EQ(test, ret, 253);
+	ret = cfg80211_defragment_element((void *)input,
+					  input, sizeof(input),
+					  data, ret,
 					  WLAN_EID_FRAGMENT);
 	KUNIT_EXPECT_EQ(test, ret, 253);
 	KUNIT_EXPECT_MEMEQ(test, data, input + 3, 253);
@@ -63,7 +68,12 @@ static void defragment_1(struct kunit *test)
 
 	ret = cfg80211_defragment_element((void *)input,
 					  input, sizeof(input),
-					  data, sizeof(input),
+					  NULL, 0,
+					  WLAN_EID_FRAGMENT);
+	KUNIT_EXPECT_EQ(test, ret, 254 + 7);
+	ret = cfg80211_defragment_element((void *)input,
+					  input, sizeof(input),
+					  data, ret,
 					  WLAN_EID_FRAGMENT);
 	/* this means the last fragment was not used */
 	KUNIT_EXPECT_EQ(test, ret, 254 + 7);
@@ -106,10 +116,15 @@ static void defragment_2(struct kunit *test)
 
 	ret = cfg80211_defragment_element((void *)input,
 					  input, sizeof(input),
-					  data, sizeof(input),
+					  NULL, 0,
 					  WLAN_EID_FRAGMENT);
 	/* this means the last fragment was not used */
 	KUNIT_EXPECT_EQ(test, ret, 254 + 255 + 1);
+	ret = cfg80211_defragment_element((void *)input,
+					  input, sizeof(input),
+					  data, ret,
+					  WLAN_EID_FRAGMENT);
+	KUNIT_EXPECT_EQ(test, ret, 254 + 255 + 1);
 	KUNIT_EXPECT_MEMEQ(test, data, input + 3, 254);
 	KUNIT_EXPECT_MEMEQ(test, data + 254, input + 257 + 2, 255);
 	KUNIT_EXPECT_MEMEQ(test, data + 254 + 255, input + 2 * 257 + 2, 1);
@@ -134,7 +149,12 @@ static void defragment_at_end(struct kunit *test)
 
 	ret = cfg80211_defragment_element((void *)input,
 					  input, sizeof(input),
-					  data, sizeof(input),
+					  NULL, 0,
+					  WLAN_EID_FRAGMENT);
+	KUNIT_EXPECT_EQ(test, ret, 254 + 7);
+	ret = cfg80211_defragment_element((void *)input,
+					  input, sizeof(input),
+					  data, ret,
 					  WLAN_EID_FRAGMENT);
 	KUNIT_EXPECT_EQ(test, ret, 254 + 7);
 	KUNIT_EXPECT_MEMEQ(test, data, input + 3, 254);
diff --git a/versions b/versions
index 321b1a1d86..4cb6dcc386 100644
--- a/versions
+++ b/versions
@@ -2,4 +2,4 @@ BACKPORTS_VERSION="(see git)"
 BACKPORTED_KERNEL_VERSION="(see git)"
 BACKPORTED_KERNEL_NAME="iwlwifi"
 BACKPORTS_BUILD_TSTAMP=__DATE__ \" \" __TIME__
-BACKPORTS_GIT_TRACKED="iwlwifi-stack-public:master:11900:92f20bb9"
+BACKPORTS_GIT_TRACKED="iwlwifi-stack-public:master:11901:eded020a"