On Thu, Jun 15, 2023 at 12:04:07PM -0600, Gustavo A. R. Silva wrote: > -Wstringop-overflow is legitimately warning us about extra_size > pontentially being zero at some point, hence potenially ending nit: checkpatch --codespell suggests: potenially -> potentially > up _allocating_ zero bytes of memory for extra pointer and then > trying to access such object in a call to copy_from_user(). > > Fix this by adding a sanity check to ensure we never end up > trying to allocate zero bytes of data for extra pointer, before > continue executing the rest of the code in the function. > > Address the following -Wstringop-overflow warning seen when built > m68k architecture with allyesconfig configuration: > from net/wireless/wext-core.c:11: > In function '_copy_from_user', > inlined from 'copy_from_user' at include/linux/uaccess.h:183:7, > inlined from 'ioctl_standard_iw_point' at net/wireless/wext-core.c:825:7: > arch/m68k/include/asm/string.h:48:25: warning: '__builtin_memset' writing 1 or more bytes into a region of size 0 overflows the destination [-Wstringop-overflow=] > 48 | #define memset(d, c, n) __builtin_memset(d, c, n) > | ^~~~~~~~~~~~~~~~~~~~~~~~~ > include/linux/uaccess.h:153:17: note: in expansion of macro 'memset' > 153 | memset(to + (n - res), 0, res); > | ^~~~~~ > In function 'kmalloc', > inlined from 'kzalloc' at include/linux/slab.h:694:9, > inlined from 'ioctl_standard_iw_point' at net/wireless/wext-core.c:819:10: > include/linux/slab.h:577:16: note: at offset 1 into destination object of size 0 allocated by '__kmalloc' > 577 | return __kmalloc(size, flags); > | ^~~~~~~~~~~~~~~~~~~~~~ > > This help with the ongoing efforts to globally enable > -Wstringop-overflow. > > Link: https://github.com/KSPP/linux/issues/315 > Signed-off-by: Gustavo A. R. Silva <gustavoars@xxxxxxxxxx> Reviewed-by: Simon Horman <simon.horman@xxxxxxxxxxxx>
