GCC 7 has a known bug where UBSAN ignores '-fwrapv' and generates false signed-overflow-UB warnings. The type mismatch between 'i' and 'nr_segs' in copy_compat_iovec_from_user() is causing such a warning, which also happens to violate uaccess rules:
lib/iov_iter.o: warning: objtool: iovec_from_user()+0x22d: call to __ubsan_handle_add_overflow() with UACCESS enabled Fix it by making the variable types match. This is similar to a previous commit: 29da93fea3ea ("mm/uaccess: Use 'unsigned long' to placate UBSAN warnings on older GCC versions") Reported-by: Randy Dunlap <rdun...@infradead.org> Signed-off-by: Josh Poimboeuf <jpoim...@redhat.com> --- lib/iov_iter.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/lib/iov_iter.c b/lib/iov_iter.c index 1635111c5bd2..2e6a42f5d1df 100644 --- a/lib/iov_iter.c +++ b/lib/iov_iter.c @@ -1656,7 +1656,8 @@ static int copy_compat_iovec_from_user(struct iovec *iov, { const struct compat_iovec __user *uiov = (const struct compat_iovec __user *)uvec; - int ret = -EFAULT, i; + int ret = -EFAULT; + unsigned long i; if (!user_access_begin(uvec, nr_segs * sizeof(*uvec))) return -EFAULT; -- 2.29.2