Patch "wifi: cfg80211: check A-MSDU format more carefully" has been added to the 6.8-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    wifi: cfg80211: check A-MSDU format more carefully

to the 6.8-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     wifi-cfg80211-check-a-msdu-format-more-carefully.patch
and it can be found in the queue-6.8 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 30198bcfdfc6260770382508b26aa86b174d1b15
Author: Johannes Berg <johannes.berg@xxxxxxxxx>
Date:   Mon Feb 26 20:34:06 2024 +0100

    wifi: cfg80211: check A-MSDU format more carefully
    
    [ Upstream commit 9ad7974856926129f190ffbe3beea78460b3b7cc ]
    
    If it looks like there's another subframe in the A-MSDU
    but the header isn't fully there, we can end up reading
    data out of bounds, only to discard later. Make this a
    bit more careful and check if the subframe header can
    even be present.
    
    Reported-by: syzbot+d050d437fe47d479d210@xxxxxxxxxxxxxxxxxxxxxxxxx
    Link: https://msgid.link/20240226203405.a731e2c95e38.I82ce7d8c0cc8970ce29d0a39fdc07f1ffc425be4@changeid
    Signed-off-by: Johannes Berg <johannes.berg@xxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/net/wireless/util.c b/net/wireless/util.c
index d1ce3bee27973..b9d15f369378b 100644
--- a/net/wireless/util.c
+++ b/net/wireless/util.c
@@ -791,15 +791,19 @@ ieee80211_amsdu_subframe_length(void *field, u8 mesh_flags, u8 hdr_type)
 
 bool ieee80211_is_valid_amsdu(struct sk_buff *skb, u8 mesh_hdr)
 {
-	int offset = 0, remaining, subframe_len, padding;
+	int offset = 0, subframe_len, padding;
 
 	for (offset = 0; offset < skb->len; offset += subframe_len + padding) {
+		int remaining = skb->len - offset;
 		struct {
 		    __be16 len;
 		    u8 mesh_flags;
 		} hdr;
 		u16 len;
 
+		if (sizeof(hdr) > remaining)
+			return false;
+
 		if (skb_copy_bits(skb, offset + 2 * ETH_ALEN, &hdr, sizeof(hdr)) < 0)
 			return false;
 
@@ -807,7 +811,6 @@ bool ieee80211_is_valid_amsdu(struct sk_buff *skb, u8 mesh_hdr)
 						      mesh_hdr);
 		subframe_len = sizeof(struct ethhdr) + len;
 		padding = (4 - subframe_len) & 0x3;
-		remaining = skb->len - offset;
 
 		if (subframe_len > remaining)
 			return false;
@@ -825,7 +828,7 @@ void ieee80211_amsdu_to_8023s(struct sk_buff *skb, struct sk_buff_head *list,
 {
 	unsigned int hlen = ALIGN(extra_headroom, 4);
 	struct sk_buff *frame = NULL;
-	int offset = 0, remaining;
+	int offset = 0;
 	struct {
 		struct ethhdr eth;
 		uint8_t flags;
@@ -839,10 +842,14 @@ void ieee80211_amsdu_to_8023s(struct sk_buff *skb, struct sk_buff_head *list,
 		copy_len = sizeof(hdr);
 
 	while (!last) {
+		int remaining = skb->len - offset;
 		unsigned int subframe_len;
 		int len, mesh_len = 0;
 		u8 padding;
 
+		if (copy_len > remaining)
+			goto purge;
+
 		skb_copy_bits(skb, offset, &hdr, copy_len);
 		if (iftype == NL80211_IFTYPE_MESH_POINT)
 			mesh_len = __ieee80211_get_mesh_hdrlen(hdr.flags);
@@ -852,7 +859,6 @@ void ieee80211_amsdu_to_8023s(struct sk_buff *skb, struct sk_buff_head *list,
 		padding = (4 - subframe_len) & 0x3;
 
 		/* the last MSDU has no padding */
-		remaining = skb->len - offset;
 		if (subframe_len > remaining)
 			goto purge;
 		/* mitigate A-MSDU aggregation injection attacks */