Re: [RFC - is this a bug?] wifi: ath10k: Asking for some light on this, please :)
On 10/25/2023 8:52 AM, Jeff Johnson wrote: > On 10/24/2023 7:37 PM, Gustavo A. R. Silva wrote: >> >> >> On 10/24/23 14:49, Johannes Berg wrote: >>> On Tue, 2023-10-24 at 14:41 -0600, Gustavo A. R. Silva wrote: It seems we run into the same issue in the function below, even in the case this `memset()` is unnecessary (which it seems it's not): 8920 memset(skb->data, 0, sizeof(*cmd)); Notice that if `cap->peer_chan_len == 0` or `cap->peer_chan_len == 1`, in the original code, we have `len == sizeof(*cmd) == 128`: >>> >>> Right. >>> - /* tdls peer update cmd has place holder for one channel*/ - chan_len = cap->peer_chan_len ? (cap->peer_chan_len - 1) : 0; - - len = sizeof(*cmd) + chan_len * sizeof(*chan); + len = struct_size(cmd, peer_capab.peer_chan_list, cap->peer_chan_len); skb = ath10k_wmi_alloc_skb(ar, len); if (!skb) which makes `round_len == roundup(len, 4) == struct_size(cmd,...,...) == 104` when `cap->peer_chan_len == 0` >>> >>> And yeah, that's really the issue, it only matters for ==0. For a moment >>> there I thought that doesn't even make sense, but it looks like it never >>> even becomes non-zero. >>> >>> No idea then, sorry. You'd hope firmware doesn't care about the actual >>> message size if the inner data says "0 entries", but who knows? And how >>> many firmware versions are there? :) >>> >>> So I guess you'd want to stay compatible, even if it means having a >>> >>> chan_len = min(cap->peer_chan_len, 1); >>> >>> for the struct_size()? >> >> Yeah, that's an alternative. >> >> I'll wait for the maintainers to chime in and see if they have a different >> opinion. > > I'm seeing clarification from the development team. > > /jeff > I was not able to get a response from the firmware team. I have gone ahead and created a series of patches to fix the remaining flexible array issues in ath10k including the one discussed here. I should be able to post those sometime this week. /jeff
Re: [RFC - is this a bug?] wifi: ath10k: Asking for some light on this, please :)
On 10/24/2023 7:37 PM, Gustavo A. R. Silva wrote: On 10/24/23 14:49, Johannes Berg wrote: On Tue, 2023-10-24 at 14:41 -0600, Gustavo A. R. Silva wrote: It seems we run into the same issue in the function below, even in the case this `memset()` is unnecessary (which it seems it's not): 8920 memset(skb->data, 0, sizeof(*cmd)); Notice that if `cap->peer_chan_len == 0` or `cap->peer_chan_len == 1`, in the original code, we have `len == sizeof(*cmd) == 128`: Right. - /* tdls peer update cmd has place holder for one channel*/ - chan_len = cap->peer_chan_len ? (cap->peer_chan_len - 1) : 0; - - len = sizeof(*cmd) + chan_len * sizeof(*chan); + len = struct_size(cmd, peer_capab.peer_chan_list, cap->peer_chan_len); skb = ath10k_wmi_alloc_skb(ar, len); if (!skb) which makes `round_len == roundup(len, 4) == struct_size(cmd,...,...) == 104` when `cap->peer_chan_len == 0` And yeah, that's really the issue, it only matters for ==0. For a moment there I thought that doesn't even make sense, but it looks like it never even becomes non-zero. No idea then, sorry. You'd hope firmware doesn't care about the actual message size if the inner data says "0 entries", but who knows? And how many firmware versions are there? :) So I guess you'd want to stay compatible, even if it means having a chan_len = min(cap->peer_chan_len, 1); for the struct_size()? Yeah, that's an alternative. I'll wait for the maintainers to chime in and see if they have a different opinion. I'm seeing clarification from the development team. /jeff
Re: [RFC - is this a bug?] wifi: ath10k: Asking for some light on this, please :)
On 10/24/23 14:49, Johannes Berg wrote: On Tue, 2023-10-24 at 14:41 -0600, Gustavo A. R. Silva wrote: It seems we run into the same issue in the function below, even in the case this `memset()` is unnecessary (which it seems it's not): 8920 memset(skb->data, 0, sizeof(*cmd)); Notice that if `cap->peer_chan_len == 0` or `cap->peer_chan_len == 1`, in the original code, we have `len == sizeof(*cmd) == 128`: Right. - /* tdls peer update cmd has place holder for one channel*/ - chan_len = cap->peer_chan_len ? (cap->peer_chan_len - 1) : 0; - - len = sizeof(*cmd) + chan_len * sizeof(*chan); + len = struct_size(cmd, peer_capab.peer_chan_list, cap->peer_chan_len); skb = ath10k_wmi_alloc_skb(ar, len); if (!skb) which makes `round_len == roundup(len, 4) == struct_size(cmd,...,...) == 104` when `cap->peer_chan_len == 0` And yeah, that's really the issue, it only matters for ==0. For a moment there I thought that doesn't even make sense, but it looks like it never even becomes non-zero. No idea then, sorry. You'd hope firmware doesn't care about the actual message size if the inner data says "0 entries", but who knows? And how many firmware versions are there? :) So I guess you'd want to stay compatible, even if it means having a chan_len = min(cap->peer_chan_len, 1); for the struct_size()? Yeah, that's an alternative. I'll wait for the maintainers to chime in and see if they have a different opinion. Thanks -- Gustavo
Re: [RFC - is this a bug?] wifi: ath10k: Asking for some light on this, please :)
[+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.ca...@sipsolutions.net/
[2]
https://lore.kernel.org/linux-hardening/07e9bb04-f9fc-46d5-bfb9-a00a63a70...@embeddedor.com/
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
Re: [RFC - is this a bug?] wifi: ath10k: Asking for some light on this, please :)
On Tue, 2023-10-24 at 14:41 -0600, Gustavo A. R. Silva wrote: > > It seems we run into the same issue in the function below, even in the > case this `memset()` is unnecessary (which it seems it's not): > > 8920 memset(skb->data, 0, sizeof(*cmd)); > > Notice that if `cap->peer_chan_len == 0` or `cap->peer_chan_len == 1`, > in the original code, we have `len == sizeof(*cmd) == 128`: Right. > - /* tdls peer update cmd has place holder for one channel*/ > - chan_len = cap->peer_chan_len ? (cap->peer_chan_len - 1) : 0; > - > - len = sizeof(*cmd) + chan_len * sizeof(*chan); > + len = struct_size(cmd, peer_capab.peer_chan_list, cap->peer_chan_len); > > skb = ath10k_wmi_alloc_skb(ar, len); > if (!skb) > > which makes `round_len == roundup(len, 4) == struct_size(cmd,...,...) == 104` > when `cap->peer_chan_len == 0` And yeah, that's really the issue, it only matters for ==0. For a moment there I thought that doesn't even make sense, but it looks like it never even becomes non-zero. No idea then, sorry. You'd hope firmware doesn't care about the actual message size if the inner data says "0 entries", but who knows? And how many firmware versions are there? :) So I guess you'd want to stay compatible, even if it means having a chan_len = min(cap->peer_chan_len, 1); for the struct_size()? johannes
Re: [RFC - is this a bug?] wifi: ath10k: Asking for some light on this, please :)
On 10/24/23 14:11, Johannes Berg wrote:
On Tue, 2023-10-24 at 13:50 -0600, 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:
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?
If we look a step further, I _think_ even that memset is unnecessary?
It seems we run into the same issue in the function below, even in the
case this `memset()` is unnecessary (which it seems it's not):
8920 memset(skb->data, 0, sizeof(*cmd));
Notice that if `cap->peer_chan_len == 0` or `cap->peer_chan_len == 1`,
in the original code, we have `len == sizeof(*cmd) == 128`:
drivers/net/wireless/ath/ath10k/wmi.c:
8911 /* tdls peer update cmd has place holder for one channel*/
8912 chan_len = cap->peer_chan_len ? (cap->peer_chan_len - 1) : 0;
8913
8914 len = sizeof(*cmd) + chan_len * sizeof(*chan);
8915
8916 skb = ath10k_wmi_alloc_skb(ar, len);
struct sk_buff *ath10k_wmi_alloc_skb(struct ath10k *ar, u32 len)
{
struct sk_buff *skb;
u32 round_len = roundup(len, 4);
skb = ath10k_htc_alloc_skb(ar, WMI_SKB_HEADROOM + round_len);
if (!skb)
return NULL;
skb_reserve(skb, WMI_SKB_HEADROOM);
if (!IS_ALIGNED((unsigned long)skb->data, 4))
ath10k_warn(ar, "Unaligned WMI skb\n");
skb_put(skb, round_len);
so `round_len == roundup(len, 4) == 128` at the moment of this
`memset()` call:
memset(skb->data, 0, round_len);
which take us back to the same problem, this time in the `memset()` above,
because after the flex-array transformation we would have:
--- a/drivers/net/wireless/ath/ath10k/wmi.c
+++ b/drivers/net/wireless/ath/ath10k/wmi.c
@@ -8905,13 +8905,10 @@ ath10k_wmi_10_4_gen_tdls_peer_update(struct ath10k *ar,
struct wmi_channel *chan;
struct sk_buff *skb;
u32 peer_qos;
- int len, chan_len;
+ size_t len;
int i;
- /* tdls peer update cmd has place holder for one channel*/
- chan_len = cap->peer_chan_len ? (cap->peer_chan_len - 1) : 0;
-
- len = sizeof(*cmd) + chan_len * sizeof(*chan);
+ len = struct_size(cmd, peer_capab.peer_chan_list, cap->peer_chan_len);
skb = ath10k_wmi_alloc_skb(ar, len);
if (!skb)
which makes `round_len == roundup(len, 4) == struct_size(cmd,...,...) == 104`
when `cap->peer_chan_len == 0`
So shouldn't the outgoing skb be exactly the same?
It seems it's not.
Anyway, just looking at the code out of curiosity, I don't actually know
anything about this driver :)
johannes
--
Gustavo
Re: [RFC - is this a bug?] wifi: ath10k: Asking for some light on this, please :)
On Tue, 2023-10-24 at 13:50 -0600, 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:
> 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?
>
If we look a step further, I _think_ even that memset is unnecessary?
struct sk_buff *ath10k_wmi_alloc_skb(struct ath10k *ar, u32 len)
{
struct sk_buff *skb;
u32 round_len = roundup(len, 4);
skb = ath10k_htc_alloc_skb(ar, WMI_SKB_HEADROOM + round_len);
if (!skb)
return NULL;
skb_reserve(skb, WMI_SKB_HEADROOM);
if (!IS_ALIGNED((unsigned long)skb->data, 4))
ath10k_warn(ar, "Unaligned WMI skb\n");
skb_put(skb, round_len);
memset(skb->data, 0, round_len);
return skb;
}
So shouldn't the outgoing skb be exactly the same?
Anyway, just looking at the code out of curiosity, I don't actually know
anything about this driver :)
johannes
