[+CC Manikanta Pubbisetty ]
As Johannes[1] pointed out, this `memset()` is probably unnecessary:
./drivers/net/wireless/ath/ath10k/wmi.c:
8920 memset(skb->data, 0, sizeof(*cmd));
However, the same exact issue[2] is present at the line below inside
function `ath10k_wmi_alloc_skb()`:
drivers/net/wireless/ath/ath10k/wmi.c:
1799 memset(skb->data, 0, round_len);
Thanks
--
Gustavo
[1] https://lore.kernel.org/linux-hardening/26b15f4702cef17fe70b496a62f03735874bd16a.camel@xxxxxxxxxxxxxxxx/
[2] https://lore.kernel.org/linux-hardening/07e9bb04-f9fc-46d5-bfb9-a00a63a707c0@xxxxxxxxxxxxxx/
On 10/24/23 13:50, Gustavo A. R. Silva wrote:
Hi all,
While working on tranforming one-element array `peer_chan_list` in
`struct wmi_tdls_peer_capabilities` into a flex-array member
7187 struct wmi_tdls_peer_capabilities {
...
7199 struct wmi_channel peer_chan_list[1];
7200 } __packed;
the following line caught my attention:
./drivers/net/wireless/ath/ath10k/wmi.c:
8920 memset(skb->data, 0, sizeof(*cmd));
Notice that before the flex-array transformation, we are zeroing 128
bytes in `skb->data` because `sizeof(*cmd) == 128`, see below:
$ pahole -C wmi_10_4_tdls_peer_update_cmd drivers/net/wireless/ath/ath10k/wmi.o
struct wmi_10_4_tdls_peer_update_cmd {
__le32 vdev_id; /* 0 4 */
struct wmi_mac_addr peer_macaddr; /* 4 8 */
__le32 peer_state; /* 12 4 */
__le32 reserved[4]; /* 16 16 */
struct wmi_tdls_peer_capabilities peer_capab; /* 32 96 */
/* size: 128, cachelines: 2, members: 5 */
};
So, after the flex-array transformation (and the necessary adjustments
to a few other lines of code) we would be zeroing 104 bytes in
`skb->data` because `sizeof(*cmd) == 104`, see below:
$ pahole -C wmi_10_4_tdls_peer_update_cmd drivers/net/wireless/ath/ath10k/wmi.o
struct wmi_10_4_tdls_peer_update_cmd {
__le32 vdev_id; /* 0 4 */
struct wmi_mac_addr peer_macaddr; /* 4 8 */
__le32 peer_state; /* 12 4 */
__le32 reserved[4]; /* 16 16 */
struct wmi_tdls_peer_capabilities peer_capab; /* 32 72 */
/* size: 104, cachelines: 2, members: 5 */
/* last cacheline: 40 bytes */
};
This difference arises because the size of the element type for the
`peer_chan_list` array, which is `sizeof(struct wmi_channel) == 24 `
$ pahole -C wmi_channel drivers/net/wireless/ath/ath10k/wmi.o
struct wmi_channel {
__le32 mhz; /* 0 4 */
__le32 band_center_freq1; /* 4 4 */
__le32 band_center_freq2; /* 8 4 */
[..]
/* 20 4 */
/* size: 24, cachelines: 1, members: 6 */
/* last cacheline: 24 bytes */
};
is included in `sizeof(*cmd)` before the transformation.
So, my question is: do we really need to zero out those extra 24 bytes in
`skb->data`? or is it rather a bug in the original code?
Thanks!
--
Gustavo
