Le 24/08/2022 à 07:56, Zhouyi Zhou a écrit :
> In function walk_hugetlb_range, the local variable err may
> be used uninitialzed when:
> ops->pte_hole in side of "else if (ops->pte_hole)" is false.
>
> Signed-off-by: Zhouyi Zhou <zhouzhouyi@xxxxxxxxx>
> ---
> Dear mm Developers:
>
> When I build kernel using "make CC=clang-14"
> the compiler complains following:
>
> CC mm/pagewalk.o
> mm/pagewalk.c:318:12: error: variable 'err' is used uninitialized whenever 'if' condition is false [-Werror,-Wsometimes-uninitialized]
> else if (ops->pte_hole)
> ^~~~~~~~~~~~~
> mm/pagewalk.c:321:7: note: uninitialized use occurs here
> if (err)
> ^~~
> mm/pagewalk.c:318:8: note: remove the 'if' if its condition is always true
> else if (ops->pte_hole)
> ^~~~~~~~~~~~~~~~~~
> mm/pagewalk.c:311:10: note: initialize the variable 'err' to silence this warning
> int err;
> ^
> = 0
> 1 error generated.
> make[1]: *** [scripts/Makefile.build:250: mm/pagewalk.o] Error 1
> make: *** [Makefile:2006: mm] Error 2
>
> I initialize that variable outside of the for loop because we can assign 0 to err
> only once in this function.
>
> After my fix, I can compile the kernel.
>
> Many Thanks
> Zhouyi
> --
> mm/pagewalk.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/pagewalk.c b/mm/pagewalk.c
> index 54b2a1beeeb3..b6eb330e8ecd 100644
> --- a/mm/pagewalk.c
> +++ b/mm/pagewalk.c
> @@ -306,9 +306,9 @@ static int walk_hugetlb_range(unsigned long addr, unsigned long end,
> unsigned long hmask = huge_page_mask(h);
> unsigned long sz = huge_page_size(h);
> const struct mm_walk_ops *ops = walk->ops;
> + int err = 0;
Why do you move it back outside of the for loop allthough it is
exclusively used inside the loop ?
>
> for (; addr < end; addr = next) {
> - int err;
Another solution would be to add an explicit else, setting err = 0 in
the if/else if sequence.
> pte_t *pte = huge_pte_offset(walk->mm, addr & hmask, sz);
>
> next = hugetlb_entry_end(h, addr, end);
