From: Johannes Berg johannes.berg@intel.com
In commit 8c89f7b3d3f2 ("mac80211: Use flex-array for radiotap header bitmap") we accidentally pointed the position to the wrong place, so we overwrite a present bitmap, and thus cause all kinds of trouble.
To see the issue, note that the previous code read:
pos = (void *)(it_present + 1);
The requirement now is that we need to calculate pos via it_optional, to not trigger the compiler hardening checks, as:
pos = (void *)&rthdr->it_optional[...];
Rewriting the original expression, we get (obviously, since that just adds "+ x - x" terms):
pos = (void *)(it_present + 1 + rthdr->it_optional - rthdr->it_optional)
and moving the "+ rthdr->it_optional" outside to be used as an array:
pos = (void *)&rthdr->it_optional[it_present + 1 - rthdr->it_optional];
The original is off by one, fix it.
Cc: stable@vger.kernel.org Fixes: 8c89f7b3d3f2 ("mac80211: Use flex-array for radiotap header bitmap") Reported-by: Sid Hayn sidhayn@gmail.com Signed-off-by: Johannes Berg johannes.berg@intel.com --- net/mac80211/rx.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/net/mac80211/rx.c b/net/mac80211/rx.c index fc5c608d02e2..3562730ea0f8 100644 --- a/net/mac80211/rx.c +++ b/net/mac80211/rx.c @@ -364,7 +364,7 @@ ieee80211_add_rx_radiotap_header(struct ieee80211_local *local, * the compiler to think we have walked past the end of the * struct member. */ - pos = (void *)&rthdr->it_optional[it_present - rthdr->it_optional]; + pos = (void *)&rthdr->it_optional[it_present + 1 - rthdr->it_optional];
/* the order of the following fields is important */
Please add my tested-by as well. I tested with and without this patch on multiple chipsets and everything appears functional now. Thanks for the quick fix!
Tested-by: Sid Hayn sidhayn@gmail.com
On Tue, Nov 9, 2021 at 4:02 AM Johannes Berg johannes@sipsolutions.net wrote:
From: Johannes Berg johannes.berg@intel.com
In commit 8c89f7b3d3f2 ("mac80211: Use flex-array for radiotap header bitmap") we accidentally pointed the position to the wrong place, so we overwrite a present bitmap, and thus cause all kinds of trouble.
To see the issue, note that the previous code read:
pos = (void *)(it_present + 1);
The requirement now is that we need to calculate pos via it_optional, to not trigger the compiler hardening checks, as:
pos = (void *)&rthdr->it_optional[...];
Rewriting the original expression, we get (obviously, since that just adds "+ x - x" terms):
pos = (void *)(it_present + 1 + rthdr->it_optional - rthdr->it_optional)
and moving the "+ rthdr->it_optional" outside to be used as an array:
pos = (void *)&rthdr->it_optional[it_present + 1 - rthdr->it_optional];
The original is off by one, fix it.
Cc: stable@vger.kernel.org Fixes: 8c89f7b3d3f2 ("mac80211: Use flex-array for radiotap header bitmap") Reported-by: Sid Hayn sidhayn@gmail.com Signed-off-by: Johannes Berg johannes.berg@intel.com
net/mac80211/rx.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/net/mac80211/rx.c b/net/mac80211/rx.c index fc5c608d02e2..3562730ea0f8 100644 --- a/net/mac80211/rx.c +++ b/net/mac80211/rx.c @@ -364,7 +364,7 @@ ieee80211_add_rx_radiotap_header(struct ieee80211_local *local, * the compiler to think we have walked past the end of the * struct member. */
pos = (void *)&rthdr->it_optional[it_present - rthdr->it_optional];
pos = (void *)&rthdr->it_optional[it_present + 1 - rthdr->it_optional]; /* the order of the following fields is important */-- 2.31.1
On Tue, Nov 09, 2021 at 10:02:04AM +0100, Johannes Berg wrote:
From: Johannes Berg johannes.berg@intel.com
In commit 8c89f7b3d3f2 ("mac80211: Use flex-array for radiotap header bitmap") we accidentally pointed the position to the wrong place, so we overwrite a present bitmap, and thus cause all kinds of trouble.
To see the issue, note that the previous code read:
pos = (void *)(it_present + 1);
The requirement now is that we need to calculate pos via it_optional, to not trigger the compiler hardening checks, as:
pos = (void *)&rthdr->it_optional[...];
Rewriting the original expression, we get (obviously, since that just adds "+ x - x" terms):
pos = (void *)(it_present + 1 + rthdr->it_optional - rthdr->it_optional)
and moving the "+ rthdr->it_optional" outside to be used as an array:
pos = (void *)&rthdr->it_optional[it_present + 1 - rthdr->it_optional];
The original is off by one, fix it.
Cc: stable@vger.kernel.org Fixes: 8c89f7b3d3f2 ("mac80211: Use flex-array for radiotap header bitmap") Reported-by: Sid Hayn sidhayn@gmail.com Signed-off-by: Johannes Berg johannes.berg@intel.com
Argh! Thank you for the fix and sorry for the trouble the earlier patch created!
Reviewed-by: Kees Cook keescook@chromium.org
-Kees
net/mac80211/rx.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/net/mac80211/rx.c b/net/mac80211/rx.c index fc5c608d02e2..3562730ea0f8 100644 --- a/net/mac80211/rx.c +++ b/net/mac80211/rx.c @@ -364,7 +364,7 @@ ieee80211_add_rx_radiotap_header(struct ieee80211_local *local, * the compiler to think we have walked past the end of the * struct member. */
- pos = (void *)&rthdr->it_optional[it_present - rthdr->it_optional];
- pos = (void *)&rthdr->it_optional[it_present + 1 - rthdr->it_optional];
/* the order of the following fields is important */ -- 2.31.1
linux-stable-mirror@lists.linaro.org
-
Johannes Berg -
Kees Cook -
Sid Hayn