[PATCH 6.8 047/143] wifi: cfg80211: check A-MSDU format more carefully

Greg Kroah-Hartman
2024-04-11T10:09:00Z

From: Johannes Berg <johannes.berg@intel.com>

[ 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@syzkaller.appspotmail.com
Link: https://msgid.link/20240226203405.a731e2c95e38.I82ce7d8c0cc8970ce29d0a39fdc07f1ffc425be4@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/wireless/util.c | 14 ++++++++++----
1 file changed, 10 insertions(+), 4 deletions(-)

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 */
--
2.43.0