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85f4c95172
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
inadvertenly introduced[3] to the codebase from now on.
Lastly, make use of the struct_size() helper to safely calculate the
allocation size for instances of struct n_hdlc_buf and avoid any potential
type mistakes[4][5].
[1] https://github.com/KSPP/linux/issues/21
[2] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
[3] commit
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| .. | ||
| hvc | ||
| ipwireless | ||
| serdev | ||
| serial | ||
| vt | ||
| amiserial.c | ||
| cyclades.c | ||
| ehv_bytechan.c | ||
| goldfish.c | ||
| isicom.c | ||
| Kconfig | ||
| Makefile | ||
| mips_ejtag_fdc.c | ||
| moxa.c | ||
| moxa.h | ||
| mxser.c | ||
| mxser.h | ||
| n_gsm.c | ||
| n_hdlc.c | ||
| n_null.c | ||
| n_r3964.c | ||
| n_tracerouter.c | ||
| n_tracesink.c | ||
| n_tracesink.h | ||
| n_tty.c | ||
| nozomi.c | ||
| pty.c | ||
| rocket_int.h | ||
| rocket.c | ||
| rocket.h | ||
| synclink_gt.c | ||
| synclink.c | ||
| synclinkmp.c | ||
| sysrq.c | ||
| tty_audit.c | ||
| tty_baudrate.c | ||
| tty_buffer.c | ||
| tty_io.c | ||
| tty_ioctl.c | ||
| tty_jobctrl.c | ||
| tty_ldisc.c | ||
| tty_ldsem.c | ||
| tty_mutex.c | ||
| tty_port.c | ||
| ttynull.c | ||
| vcc.c | ||