Under CONFIG_FORTIFY_SOURCE, memcpy() will check the size of destination and source buffers. Defining kernel_headers_data as "char" would trip this check. Since these addresses are treated as byte arrays, define them as arrays (as done everywhere else). This was seen with: $ cat /sys/kernel/kheaders.tar.xz >> /dev/null detected buffer overflow in memcpy kernel BUG at lib/string_helpers.c:1027! ... RIP: 0010:fortify_panic+0xf/0x20 [...] Call Trace: <TASK> ikheaders_read+0x45/0x50 [kheaders] kernfs_fop_read_iter+0x1a4/0x2f0 ... Reported-by: Jakub Kicinski <kuba@xxxxxxxxxx> Link: https://lore.kernel.org/bpf/20230302112130.6e402a98@xxxxxxxxxx/ Tested-by: Jakub Kicinski <kuba@xxxxxxxxxx> Fixes: 43d8ce9d65a5 ("Provide in-kernel headers to make extending kernel easier") Cc: Joel Fernandes (Google) <joel@xxxxxxxxxxxxxxxxx> Cc: stable@xxxxxxxxxxxxxxx Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx> --- kernel/kheaders.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/kernel/kheaders.c b/kernel/kheaders.c index 8f69772af77b..42163c9e94e5 100644 --- a/kernel/kheaders.c +++ b/kernel/kheaders.c @@ -26,15 +26,15 @@ asm ( " .popsection \n" ); -extern char kernel_headers_data; -extern char kernel_headers_data_end; +extern char kernel_headers_data[]; +extern char kernel_headers_data_end[]; static ssize_t ikheaders_read(struct file *file, struct kobject *kobj, struct bin_attribute *bin_attr, char *buf, loff_t off, size_t len) { - memcpy(buf, &kernel_headers_data + off, len); + memcpy(buf, &kernel_headers_data[off], len); return len; } @@ -48,8 +48,8 @@ static struct bin_attribute kheaders_attr __ro_after_init = { static int __init ikheaders_init(void) { - kheaders_attr.size = (&kernel_headers_data_end - - &kernel_headers_data); + kheaders_attr.size = (kernel_headers_data_end - + kernel_headers_data); return sysfs_create_bin_file(kernel_kobj, &kheaders_attr); } -- 2.34.1
