From: Gustavo A. R. Silva Date: Thu, 16 Jan 2020 22:03:27 +0000 (-0600) Subject: USB: serial: garmin_gps: Use flexible-array member X-Git-Tag: v5.6-rc1~140^2^2~6 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=50c3c5e1c1b000d6a321ffdc0003bc6b7ac0b0e5;p=thirdparty%2Flinux.git USB: serial: garmin_gps: Use flexible-array member 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 Signed-off-by: Johan Hovold --- diff --git a/drivers/usb/serial/garmin_gps.c b/drivers/usb/serial/garmin_gps.c index 633550ec30255..ffd9841421717 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 */