wifi: mwifiex: Fix tlv_buf_left calculation and replace one-element array

In a TLV encoding scheme, the Length part represents the length after the header containing the values for type and length. In this case, tlv_len should be:

tlv_len == (sizeof(*tlv_rxba) - 1) - sizeof(tlv_rxba->header) + tlv_bitmap_len

Notice that the - 1 accounts for the one-element array bitmap, which 1-byte size is already included in sizeof(*tlv_rxba).

So, if the above is correct, there is a double-counting of some members in struct mwifiex_ie_types_rxba_sync, when tlv_buf_left and tmp are calculated:

968 tlv_buf_left -= (sizeof(*tlv_rxba) + tlv_len);
969 tmp = (u8 *)tlv_rxba + tlv_len + sizeof(*tlv_rxba);

in specific, members:

drivers/net/wireless/marvell/mwifiex/fw.h:777

 777         u8 mac[ETH_ALEN];
 778         u8 tid;
 779         u8 reserved;
 780         __le16 seq_num;
 781         __le16 bitmap_len;

This is clearly wrong, and affects the subsequent decoding of data from event_buf through tlv_rxba:

970 tlv_rxba = (struct mwifiex_ie_types_rxba_sync *)tmp;

Fix this by using sizeof(tlv_rxba->header) instead of sizeof(*tlv_rxba) in the calculation of tlv_buf_left and tmp.

This results in the following binary differences before/after changes:

| drivers/net/wireless/marvell/mwifiex/11n_rxreorder.o
| @@ -4698,11 +4698,11 @@
|                 tlv_buf_left -= (sizeof(tlv_rxba->header) + tlv_len);
| -    1da7:      lea    -0x11(%rbx),%edx
| +    1da7:      lea    -0x4(%rbx),%edx
|      1daa:      movzwl %bp,%eax
|  drivers/net/wireless/marvell/mwifiex/11n_rxreorder.c:969
|                 tmp = (u8 *)tlv_rxba  + sizeof(tlv_rxba->header) + tlv_len;
| -    1dad:      lea    0x11(%r15,%rbp,1),%r15
| +    1dad:      lea    0x4(%r15,%rbp,1),%r15
|  drivers/net/wireless/marvell/mwifiex/11n_rxreorder.c:968
|                 tlv_buf_left -= (sizeof(tlv_rxba->header) + tlv_len);
|      1db2:      mov    %edx,%ebx

The above reflects the desired change: avoid counting 13 too bytes; which is the total size of the double-counted members in struct mwifiex_ie_types_rxba_sync:

$ pahole -C mwifiex_ie_types_rxba_sync drivers/net/wireless/marvell/mwifiex/11n_rxreorder.o
struct mwifiex_ie_types_rxba_sync {
        struct mwifiex_ie_types_header header;           /*     0     4 */

     |-----------------------------------------------------------------------
     |  u8                         mac[6];               /*     4     6 */  |
     |  u8                         tid;                  /*    10     1 */  |
     |  u8                         reserved;             /*    11     1 */  |
     |  __le16                     seq_num;              /*    12     2 */  |
     |  __le16                     bitmap_len;           /*    14     2 */  |
     |  u8                         bitmap[1];            /*    16     1 */  |
     |----------------------------------------------------------------------|
                                                                  | 13 bytes|
                                                                  -----------

        /* size: 17, cachelines: 1, members: 7 */
        /* last cacheline: 17 bytes */
} __attribute__((__packed__));

Fixes 99ffe72cdae4 ("mwifiex: process rxba_sync event")

Cc [email protected]

Signed-off-by Gustavo A. R. Silva <[email protected]>

---
 drivers/net/wireless/marvell/mwifiex/11n_rxreorder.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

drivers/net/wireless/marvell/mwifiex/11n_rxreorder.c +2 -3

index 391793a16adc..d1d3632a3ed7 100644
@@ -965,8 +965,8 @@ void mwifiex_11n_rxba_sync_event(struct mwifiex_private *priv,
                        }
                }
 
-               tlv_buf_left -= (sizeof(*tlv_rxba) + tlv_len);
-               tmp = (u8 *)tlv_rxba + tlv_len + sizeof(*tlv_rxba);
+               tlv_buf_left -= (sizeof(tlv_rxba->header) + tlv_len);
+               tmp = (u8 *)tlv_rxba  + sizeof(tlv_rxba->header) + tlv_len;
                tlv_rxba = (struct mwifiex_ie_types_rxba_sync *)tmp;
        }
 }
--

2.34.1

One-element and zero-length arrays are deprecated. So, replace one-element array in struct mwifiex_ie_types_rxba_sync with flexible-array member, and refactor the rest of the code, accordingly.

This results in no differences in binary output.

Signed-off-by Gustavo A. R. Silva <[email protected]>

---
 drivers/net/wireless/marvell/mwifiex/11n_rxreorder.c | 2 +-
 drivers/net/wireless/marvell/mwifiex/fw.h            | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

drivers/net/wireless/marvell/mwifiex/11n_rxreorder.c +1 -1

index d1d3632a3ed7..735aac52bdc4 100644
@@ -918,7 +918,7 @@ void mwifiex_11n_rxba_sync_event(struct mwifiex_private *priv,
 
        mwifiex_dbg_dump(priv->adapter, EVT_D, "RXBA_SYNC event:",
                         event_buf, len);
-       while (tlv_buf_left >= sizeof(*tlv_rxba)) {
+       while (tlv_buf_left > sizeof(*tlv_rxba)) {
                tlv_type = le16_to_cpu(tlv_rxba->header.type);
                tlv_len  = le16_to_cpu(tlv_rxba->header.len);
                if (tlv_type != TLV_TYPE_RXBA_SYNC) {

drivers/net/wireless/marvell/mwifiex/fw.h +1 -2

index f2168fac95ed..8e6db904e5b2 100644
@@ -779,7 +779,7 @@ struct mwifiex_ie_types_rxba_sync {
        u8 reserved;
        __le16 seq_num;
        __le16 bitmap_len;
-       u8 bitmap[1];
+       u8 bitmap[];
 } __packed;
 
 struct chan_band_param_set {
--

2.34.1

Add sanity checks for both tlv_len and tlv_bitmap_len before decoding data from event_buf.

This prevents any malicious or buggy firmware from overflowing event_buf through large values for tlv_len or tlv_bitmap_len.

Suggested-by Dan Williams <[email protected]>

Signed-off-by Gustavo A. R. Silva <[email protected]>

---
 .../net/wireless/marvell/mwifiex/11n_rxreorder.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

drivers/net/wireless/marvell/mwifiex/11n_rxreorder.c +16 -1

index 735aac52bdc4..9ee3b9f1e9ce 100644
@@ -921,6 +921,14 @@ void mwifiex_11n_rxba_sync_event(struct mwifiex_private *priv,
        while (tlv_buf_left > sizeof(*tlv_rxba)) {
                tlv_type = le16_to_cpu(tlv_rxba->header.type);
                tlv_len  = le16_to_cpu(tlv_rxba->header.len);
+               if (size_add(sizeof(tlv_rxba->header), tlv_len) > tlv_buf_left) {
+                       mwifiex_dbg(priv->adapter, WARN,
+                                   "TLV size (%ld) overflows event_buf (%d)\n",
+                                   size_add(sizeof(tlv_rxba->header), tlv_len),
+                                   tlv_buf_left);
+                       return;
+               }
+
                if (tlv_type != TLV_TYPE_RXBA_SYNC) {
                        mwifiex_dbg(priv->adapter, ERROR,
                                    "Wrong TLV id=0x%x\n", tlv_type);

@@ -929,6 +937,14 @@ void mwifiex_11n_rxba_sync_event(struct mwifiex_private *priv,
 
                tlv_seq_num = le16_to_cpu(tlv_rxba->seq_num);
                tlv_bitmap_len = le16_to_cpu(tlv_rxba->bitmap_len);
+               if (size_add(sizeof(*tlv_rxba), tlv_bitmap_len) > tlv_buf_left) {
+                       mwifiex_dbg(priv->adapter, WARN,
+                                   "TLV size (%ld) overflows event_buf (%d)\n",
+                                   size_add(sizeof(*tlv_rxba), tlv_bitmap_len),
+                                   tlv_buf_left);
+                       return;
+               }
+
                mwifiex_dbg(priv->adapter, INFO,
                            "%pM tid=%d seq_num=%d bitmap_len=%d\n",
                            tlv_rxba->mac, tlv_rxba->tid, tlv_seq_num,
--

2.34.1