diff mbox series

[v2,next] cxgb4/ch_ktls: Fix undefined behavior bug in struct chcr_ktls_ofld_ctx_tx

Message ID ZRvzdlvlbX4+eIln@work
State New
Headers
Series [v2,next] cxgb4/ch_ktls: Fix undefined behavior bug in struct chcr_ktls_ofld_ctx_tx |

Commit Message

Gustavo A. R. Silva Oct. 3, 2023, 10:56 a.m. UTC 
  `struct tls_offload_context_tx` is a flexible structure, which means
that it contains a flexible-array member at the bottom. This could
potentially lead to an overwrite of the objects following `base` in
`struct chcr_ktls_ofld_ctx_tx` at run-time.

Notice that flexible-array member `driver_state` in `struct
tls_offload_context_tx` can grow up to 16 bytes:

| include/net/tls.h-170:
| #define TLS_DRIVER_STATE_SIZE_TX  16

| include/net/tls.h-173:
| #define TLS_OFFLOAD_CONTEXT_SIZE_TX                                     \
|	(sizeof(struct tls_offload_context_tx) + TLS_DRIVER_STATE_SIZE_TX)

| net/tls/tls_device.c-1119:
| offload_ctx = kzalloc(TLS_OFFLOAD_CONTEXT_SIZE_TX, GFP_KERNEL);

Fix this by placing the declaration of object `base` at the end of
`struct chcr_ktls_ofld_ctx_tx`.

-Wflex-array-member-not-at-end is coming in GCC-14, and we are getting
ready to enable it globally.

Fixes: 34aba2c45024 ("cxgb4/chcr : Register to tls add and del callback")
Cc: stable@vger.kernel.org
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
---
Changes in v2:
 - Update changelog text: mention -Wflex-array-member-not-at-end.

v1:
 - Link: https://lore.kernel.org/linux-hardening/ZRvyysCUTqA7aXN4@work/

 drivers/net/ethernet/chelsio/inline_crypto/ch_ktls/chcr_ktls.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

Sabrina Dubroca Oct. 3, 2023, 4:58 p.m. UTC | #1 
2023-10-03, 12:56:54 +0200, Gustavo A. R. Silva wrote:
> `struct tls_offload_context_tx` is a flexible structure, which means
> that it contains a flexible-array member at the bottom. This could
> potentially lead to an overwrite of the objects following `base` in
> `struct chcr_ktls_ofld_ctx_tx` at run-time.
> 
> Notice that flexible-array member `driver_state` in `struct
> tls_offload_context_tx` can grow up to 16 bytes:
> 
> | include/net/tls.h-170:
> | #define TLS_DRIVER_STATE_SIZE_TX  16
> 
> | include/net/tls.h-173:
> | #define TLS_OFFLOAD_CONTEXT_SIZE_TX                                     \
> |	(sizeof(struct tls_offload_context_tx) + TLS_DRIVER_STATE_SIZE_TX)
> 
> | net/tls/tls_device.c-1119:
> | offload_ctx = kzalloc(TLS_OFFLOAD_CONTEXT_SIZE_TX, GFP_KERNEL);
> 
> Fix this by placing the declaration of object `base` at the end of
> `struct chcr_ktls_ofld_ctx_tx`.

AFAIU, chcr_ktls_ofld_ctx_tx just misuses the extra space allocated by
tls_set_device_offload. There's no bug, but the code is a bit
confusing. I don't think this patch works, since chcr_ktls doesn't
allocate its own memory for chcr_ktls_ofld_ctx_tx.

As part of a series of cleanups that I'll submit soon (hopefully this
week), I updated chcr_ktls to use the driver_state part of
tls_offload_context_tx (instead of the cast in
chcr_get_ktls_tx_context), and then removed the flexarrays from
tls_offload_context_tx and tls_offload_context_rx (since they're
actually a fixed size).
diff mbox series

Patch

diff --git a/drivers/net/ethernet/chelsio/inline_crypto/ch_ktls/chcr_ktls.h b/drivers/net/ethernet/chelsio/inline_crypto/ch_ktls/chcr_ktls.h
index 10572dc55365..35e34e3db663 100644
--- a/drivers/net/ethernet/chelsio/inline_crypto/ch_ktls/chcr_ktls.h
+++ b/drivers/net/ethernet/chelsio/inline_crypto/ch_ktls/chcr_ktls.h
@@ -68,8 +68,8 @@  struct chcr_ktls_info {
 };
 
 struct chcr_ktls_ofld_ctx_tx {
-	struct tls_offload_context_tx base;
 	struct chcr_ktls_info *chcr_info;
+	struct tls_offload_context_tx base;
 };
 
 struct chcr_ktls_uld_ctx {