Messages in this thread Patch in this message | | | Date | Thu, 16 Jan 2020 16:03:27 -0600 | From | "Gustavo A. R. Silva" <> | Subject | [PATCH] USB: serial: garmin_gps: Use flexible-array member |
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Old code in the kernel uses 1-byte and 0-byte arrays to indicate the presence of a "variable length array":
struct something { int length; u8 data[1]; };
struct something *instance;
instance = kmalloc(sizeof(*instance) + size, GFP_KERNEL); instance->length = size; memcpy(instance->data, source, size);
There is also 0-byte arrays. Both cases pose confusion for things like sizeof(), CONFIG_FORTIFY_SOURCE, etc.[1] Instead, the preferred mechanism to declare variable-length types such as the one above is a flexible array member[2] which need to be the last member of a structure and empty-sized:
struct something { int stuff; u8 data[]; };
Also, by making use of the mechanism above, we will get a compiler warning in case the flexible array does not occur last in the structure, which will help us prevent some kind of undefined behavior bugs from being unadvertenly introduced[3] to the codebase from now on.
[1] https://github.com/KSPP/linux/issues/21 [2] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html [3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour")
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com> --- drivers/usb/serial/garmin_gps.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/usb/serial/garmin_gps.c b/drivers/usb/serial/garmin_gps.c index 633550ec3025..ffd984142171 100644 --- a/drivers/usb/serial/garmin_gps.c +++ b/drivers/usb/serial/garmin_gps.c @@ -104,7 +104,7 @@ struct garmin_packet { int seq; /* the real size of the data array, always > 0 */ int size; - __u8 data[1]; + __u8 data[]; }; /* structure used to keep the current state of the driver */ -- 2.23.0
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