@@ -163,6 +163,7 @@ int rds_info_getsockopt(struct socket *sock, int optname, char __user *optval,
unsigned long nr_pages = 0;
unsigned long start;
rds_info_func func;
+ unsigned long sum;
struct page **pages = NULL;
int ret;
int len;
@@ -175,7 +176,8 @@ int rds_info_getsockopt(struct socket *sock, int optname, char __user *optval,
/* check for all kinds of wrapping and the like */
start = (unsigned long)optval;
- if (len < 0 || len > INT_MAX - PAGE_SIZE + 1 || start + len < start) {
+ if (len < 0 || len > INT_MAX - PAGE_SIZE + 1 ||
+ check_add_overflow(start, len, &sum)) {
ret = -EINVAL;
goto out;
}
@@ -184,7 +186,7 @@ int rds_info_getsockopt(struct socket *sock, int optname, char __user *optval,
if (len == 0)
goto call_func;
- nr_pages = (PAGE_ALIGN(start + len) - (start & PAGE_MASK))
+ nr_pages = (PAGE_ALIGN(sum) - (start & PAGE_MASK))
>> PAGE_SHIFT;
pages = kmalloc_array(nr_pages, sizeof(struct page *), GFP_KERNEL);
In an effort to separate intentional arithmetic wrap-around from unexpected wrap-around, we need to refactor places that depend on this kind of math. One of the most common code patterns of this is: VAR + value < VAR Notably, this is considered "undefined behavior" for signed and pointer types, which the kernel works around by using the -fno-strict-overflow option in the build[1] (which used to just be -fwrapv). Regardless, we want to get the kernel source to the position where we can meaningfully instrument arithmetic wrap-around conditions and catch them when they are unexpected, regardless of whether they are signed[2], unsigned[3], or pointer[4] types. Refactor open-coded unsigned wrap-around addition test to use check_add_overflow(), retaining the result for later usage (which removes the redundant open-coded addition). This paves the way to enabling the unsigned wrap-around sanitizer[2] in the future. Link: https://git.kernel.org/linus/68df3755e383e6fecf2354a67b08f92f18536594 [1] Link: https://github.com/KSPP/linux/issues/26 [2] Link: https://github.com/KSPP/linux/issues/27 [3] Link: https://github.com/KSPP/linux/issues/344 [4] Cc: Santosh Shilimkar <santosh.shilimkar@oracle.com> Cc: "David S. Miller" <davem@davemloft.net> Cc: Eric Dumazet <edumazet@google.com> Cc: Jakub Kicinski <kuba@kernel.org> Cc: Paolo Abeni <pabeni@redhat.com> Cc: netdev@vger.kernel.org Cc: linux-rdma@vger.kernel.org Cc: rds-devel@oss.oracle.com Signed-off-by: Kees Cook <keescook@chromium.org> --- net/rds/info.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)