On Tue, Sep 12, 2023 at 12:15:43PM -0700, Nathan Chancellor wrote:
> When building bcachefs for 32-bit ARM, there is a warning when using
> min() to compare a variable of type 'size_t' with an expression of type
> 'unsigned long':
>
> fs/bcachefs/checksum.c:142:22: error: comparison of distinct pointer types
> ('typeof (len) *' (aka 'unsigned int *') and 'typeof (((1UL) << 12) - offset)
> *' (aka 'unsigned long *')) [-Werror,-Wcompare-distinct-pointer-types]
> 142 | unsigned pg_len = min(len, PAGE_SIZE -
> offset);
> |
> ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
> include/linux/minmax.h:69:19: note: expanded from macro 'min'
> 69 | #define min(x, y) __careful_cmp(x, y, <)
> | ^~~~~~~~~~~~~~~~~~~~~~
> include/linux/minmax.h:38:24: note: expanded from macro '__careful_cmp'
> 38 | __builtin_choose_expr(__safe_cmp(x, y), \
> | ^~~~~~~~~~~~~~~~
> include/linux/minmax.h:28:4: note: expanded from macro '__safe_cmp'
> 28 | (__typecheck(x, y) && __no_side_effects(x, y))
> | ^~~~~~~~~~~~~~~~~
> include/linux/minmax.h:22:28: note: expanded from macro '__typecheck'
> 22 | (!!(sizeof((typeof(x) *)1 == (typeof(y) *)1)))
> | ~~~~~~~~~~~~~~ ^ ~~~~~~~~~~~~~~
> 1 error generated.
>
> On 64-bit architectures, size_t is 'unsigned long', so there is no
> warning when comparing these two expressions. Use min_t(size_t, ...) for
> this situation, eliminating the warning.
>
> Fixes: 1fb50457684f ("bcachefs: Fix memory corruption in encryption path")
> Signed-off-by: Nathan Chancellor <[email protected]>
Reviewed-by: Justin Stitt <[email protected]>
> ---
> fs/bcachefs/checksum.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/bcachefs/checksum.c b/fs/bcachefs/checksum.c
> index 36939020f67d..ff0c3cd39ee2 100644
> --- a/fs/bcachefs/checksum.c
> +++ b/fs/bcachefs/checksum.c
> @@ -139,7 +139,7 @@ static inline int do_encrypt(struct crypto_sync_skcipher
> *tfm,
>
> for (i = 0; i < pages; i++) {
> unsigned offset = offset_in_page(buf);
> - unsigned pg_len = min(len, PAGE_SIZE - offset);
> + unsigned pg_len = min_t(size_t, len, PAGE_SIZE -
> offset);
>
> sg_set_page(sg + i, vmalloc_to_page(buf), pg_len,
> offset);
> buf += pg_len;
>
> --
> 2.42.0
>
