net: wwan: t7xx: Add __counted_by for struct t7xx_fsm_event and use struct_size()

Prepare for the coming implementation by GCC and Clang of the __counted_by
attribute. Flexible array members annotated with __counted_by can have
their accesses bounds-checked at run-time via CONFIG_UBSAN_BOUNDS (for
array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
functions).

While there, use struct_size() helper, instead of the open-coded
version, to calculate the size for the allocation of the whole
flexible structure, including of course, the flexible-array member.

This code was found with the help of Coccinelle, and audited and
fixed manually.

Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/wwan/t7xx/t7xx_state_monitor.c b/drivers/net/wwan/t7xx/t7xx_state_monitor.c
index 80edb8e75a6ad7b0207e069ec96b34ebfa507699..0bc97430211bf2e79b8b48826db898c4d0c80fa3 100644 (file)
--- a/drivers/net/wwan/t7xx/t7xx_state_monitor.c
+++ b/drivers/net/wwan/t7xx/t7xx_state_monitor.c
@@ -445,7 +445,8 @@ int t7xx_fsm_append_event(struct t7xx_fsm_ctl *ctl, enum t7xx_fsm_event_state ev
                return -EINVAL;
        }
 
-       event = kmalloc(sizeof(*event) + length, in_interrupt() ? GFP_ATOMIC : GFP_KERNEL);
+       event = kmalloc(struct_size(event, data, length),
+                       in_interrupt() ? GFP_ATOMIC : GFP_KERNEL);
        if (!event)
                return -ENOMEM;
 

diff --git a/drivers/net/wwan/t7xx/t7xx_state_monitor.h b/drivers/net/wwan/t7xx/t7xx_state_monitor.h
index b6e76f3903c892d3c3c063dc8d62d9ad8e1850ee..b0b3662ae6d72e58a0e10e1bff14876de53780bc 100644 (file)
--- a/drivers/net/wwan/t7xx/t7xx_state_monitor.h
+++ b/drivers/net/wwan/t7xx/t7xx_state_monitor.h
@@ -102,7 +102,7 @@ struct t7xx_fsm_event {
        struct list_head        entry;
        enum t7xx_fsm_event_state event_id;
        unsigned int            length;
-       unsigned char           data[];
+       unsigned char           data[] __counted_by(length);
 };
 
 struct t7xx_fsm_command {