* [PATCH] loop: avoid out-of-range warning
@ 2021-09-27 9:43 Arnd Bergmann
2021-09-27 9:51 ` Martijn Coenen
0 siblings, 1 reply; 3+ messages in thread
From: Arnd Bergmann @ 2021-09-27 9:43 UTC (permalink / raw)
To: Jens Axboe, Nathan Chancellor, Nick Desaulniers, Martijn Coenen
Cc: Arnd Bergmann, Tetsuo Handa, Dan Schatzberg, linux-block,
linux-kernel, llvm
From: Arnd Bergmann <arnd@arndb.de>
clang warns that the sanity check for page size always succeeds
when building with 64KB pages:
drivers/block/loop.c:282:27: error: result of comparison of constant 65536 with expression of type 'unsigned short' is always false [-Werror,-Wtautological-constant-out-of-range-compare]
if (bsize < 512 || bsize > PAGE_SIZE || !is_power_of_2(bsize))
~~~~~ ^ ~~~~~~~~~
There is nothing wrong here, so just shut up the check by changing
the type of the bsize argument.
Fixes: 3448914e8cc5 ("loop: Add LOOP_CONFIGURE ioctl")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
drivers/block/loop.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 7bf4686af774..51315a93b399 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -277,7 +277,7 @@ static void __loop_update_dio(struct loop_device *lo, bool dio)
* @bsize: size to validate
*/
static int
-loop_validate_block_size(unsigned short bsize)
+loop_validate_block_size(unsigned int bsize)
{
if (bsize < 512 || bsize > PAGE_SIZE || !is_power_of_2(bsize))
return -EINVAL;
--
2.29.2
^ permalink raw reply related [flat|nested] 3+ messages in thread* Re: [PATCH] loop: avoid out-of-range warning
2021-09-27 9:43 [PATCH] loop: avoid out-of-range warning Arnd Bergmann
@ 2021-09-27 9:51 ` Martijn Coenen
2021-09-27 11:16 ` Tetsuo Handa
0 siblings, 1 reply; 3+ messages in thread
From: Martijn Coenen @ 2021-09-27 9:51 UTC (permalink / raw)
To: Arnd Bergmann
Cc: Jens Axboe, Nathan Chancellor, Nick Desaulniers, Arnd Bergmann,
Tetsuo Handa, Dan Schatzberg, linux-block, LKML, llvm
Thanks!
On Mon, Sep 27, 2021 at 11:43 AM Arnd Bergmann <arnd@kernel.org> wrote:
>
> From: Arnd Bergmann <arnd@arndb.de>
>
> clang warns that the sanity check for page size always succeeds
> when building with 64KB pages:
>
> drivers/block/loop.c:282:27: error: result of comparison of constant 65536 with expression of type 'unsigned short' is always false [-Werror,-Wtautological-constant-out-of-range-compare]
> if (bsize < 512 || bsize > PAGE_SIZE || !is_power_of_2(bsize))
> ~~~~~ ^ ~~~~~~~~~
>
> There is nothing wrong here, so just shut up the check by changing
> the type of the bsize argument.
>
> Fixes: 3448914e8cc5 ("loop: Add LOOP_CONFIGURE ioctl")
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Martijkn Coenen <maco@android.com>
> ---
> drivers/block/loop.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/block/loop.c b/drivers/block/loop.c
> index 7bf4686af774..51315a93b399 100644
> --- a/drivers/block/loop.c
> +++ b/drivers/block/loop.c
> @@ -277,7 +277,7 @@ static void __loop_update_dio(struct loop_device *lo, bool dio)
> * @bsize: size to validate
> */
> static int
> -loop_validate_block_size(unsigned short bsize)
> +loop_validate_block_size(unsigned int bsize)
> {
> if (bsize < 512 || bsize > PAGE_SIZE || !is_power_of_2(bsize))
> return -EINVAL;
> --
> 2.29.2
>
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH] loop: avoid out-of-range warning
2021-09-27 9:51 ` Martijn Coenen
@ 2021-09-27 11:16 ` Tetsuo Handa
0 siblings, 0 replies; 3+ messages in thread
From: Tetsuo Handa @ 2021-09-27 11:16 UTC (permalink / raw)
To: Martijn Coenen, Arnd Bergmann
Cc: Jens Axboe, Nathan Chancellor, Nick Desaulniers, Arnd Bergmann,
Dan Schatzberg, linux-block, LKML, llvm
Well, you found a bug here.
lo_simple_ioctl(LOOP_SET_BLOCK_SIZE) passes "unsigned long arg" to
loop_validate_block_size() via loop_set_block_size(), and uses only
lower 32bits. "(lo->lo_queue->limits.logical_block_size == arg)" is
failing to "return 0;" if lower 32bits are the same but higher 32bits
are not 0. Shouldn't we also check that higher 32bits are 0, by either
making loop_validate_block_size() to accept "unsigned long" or making
loop_set_block_size() return -EINVAL if larger than UINT_MAX ?
> There is nothing wrong here, so just shut up the check by changing
> the type of the bsize argument.
I think there is something wrong here.
Since "unsigned short bsize" checked only lower 16bits, a fuzzer can
pass e.g. 0xDEAD0200 (which is not a is_power_of_2() 32bits value) to
blk_queue_logical_block_size(lo->lo_queue, arg);
blk_queue_physical_block_size(lo->lo_queue, arg);
blk_queue_io_min(lo->lo_queue, arg);
and confuse the system?
^ permalink raw reply [flat|nested] 3+ messages in thread
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2021-09-27 9:43 [PATCH] loop: avoid out-of-range warning Arnd Bergmann
2021-09-27 9:51 ` Martijn Coenen
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