Re: [PATCH 2/3] mm: vmalloc: fix vmap_ram_vread_iter() return value

Lorenzo Stoakes
2023-03-23T12:05:34Z

On Thu, Mar 23, 2023 at 12:58:35PM +0100, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@arndb.de>
>
> The error handling in vmap_ram_vread_iter() can return an
> uninitialized value in some cases:
>
> mm/vmalloc.c:3539:6: error: variable 'remains' is used uninitialized whenever 'if' condition is true [-Werror,-Wsometimes-uninitialized]
> if (!vb)
> ^~~
> mm/vmalloc.c:3587:17: note: uninitialized use occurs here
> return count - remains + zero_iter(iter, remains);
> ^~~~~~~
>
> Move the initialization up a few lines.
>
> Fixes: d9cab54f7737 ("mm: vmalloc: convert vread() to vread_iter()")
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
> mm/vmalloc.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index ebfa1e9fe6f9..fb216495fe5a 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -3521,7 +3521,7 @@ static size_t vmap_ram_vread_iter(struct iov_iter *iter, const char *addr,
> struct vmap_block *vb;
> unsigned long offset;
> unsigned int rs, re;
> - size_t remains, n;
> + size_t remains = count, n;
>
> /*
> * If it's area created by vm_map_ram() interface directly, but
> @@ -3545,7 +3545,6 @@ static size_t vmap_ram_vread_iter(struct iov_iter *iter, const char *addr,
> goto finished_zero;
> }
>
> - remains = count;
> for_each_set_bitrange(rs, re, vb->used_map, VMAP_BBMAP_BITS) {
> size_t copied;
>
> --
> 2.39.2
>
>

This was also already fixed in a more recent version of this patch set, in
v5 I believe. Again apologies for this!

Latest version at