[PATCH v1 1/1] libceph: Amend checking to fix `make W=1` build breakage

[PATCH v1 1/1] libceph: Amend checking to fix `make W=1` build breakage

[Andy Shevchenko]

In a few cases the code compares 32-bit value to a SIZE_MAX derived
constant which is much higher than that value on 64-bit platforms,
Clang, in particular, is not happy about this

net/ceph/osdmap.c:1441:10: error: result of comparison of constant 4611686018427387891 with expression of type 'u32' (aka 'unsigned int') is always false [-Werror,-Wtautological-constant-out-of-range-compare]
 1441 |         if (len > (SIZE_MAX - sizeof(*pg)) / sizeof(u32))
      |             ~~~ ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
net/ceph/osdmap.c:1624:10: error: result of comparison of constant 2305843009213693945 with expression of type 'u32' (aka 'unsigned int') is always false [-Werror,-Wtautological-constant-out-of-range-compare]
 1624 |         if (len > (SIZE_MAX - sizeof(*pg)) / (2 * sizeof(u32)))
      |             ~~~ ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

fs/ceph/snap.c:377:10: error: result of comparison of constant 2305843009213693948 with expression of type 'u32' (aka 'unsigned int') is always false [-Werror,-Wtautological-constant-out-of-range-compare]
  377 |         if (num > (SIZE_MAX - sizeof(*snapc)) / sizeof(u64))
      |             ~~~ ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Fix this by casting to size_t. Note, that possible replacement of SIZE_MAX
by U32_MAX may lead to the behaviour changes on the corner cases.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
---
 net/ceph/osdmap.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/ceph/osdmap.c b/net/ceph/osdmap.c
index 295098873861..8e7cb2fde6f1 100644
--- a/net/ceph/osdmap.c
+++ b/net/ceph/osdmap.c
@@ -1438,7 +1438,7 @@ static struct ceph_pg_mapping *__decode_pg_temp(void **p, void *end,
 	ceph_decode_32_safe(p, end, len, e_inval);
 	if (len == 0 && incremental)
 		return NULL;	/* new_pg_temp: [] to remove */
-	if (len > (SIZE_MAX - sizeof(*pg)) / sizeof(u32))
+	if ((size_t)len > (SIZE_MAX - sizeof(*pg)) / sizeof(u32))
 		return ERR_PTR(-EINVAL);
 
 	ceph_decode_need(p, end, len * sizeof(u32), e_inval);
@@ -1621,7 +1621,7 @@ static struct ceph_pg_mapping *__decode_pg_upmap_items(void **p, void *end,
 	u32 len, i;
 
 	ceph_decode_32_safe(p, end, len, e_inval);
-	if (len > (SIZE_MAX - sizeof(*pg)) / (2 * sizeof(u32)))
+	if ((size_t)len > (SIZE_MAX - sizeof(*pg)) / (2 * sizeof(u32)))
 		return ERR_PTR(-EINVAL);
 
 	ceph_decode_need(p, end, 2 * len * sizeof(u32), e_inval);
-- 
2.50.1

Re: [PATCH v1 1/1] libceph: Amend checking to fix `make W=1` build breakage

[Viacheslav Dubeyko]

On Mon, 2025-11-10 at 15:46 +0100, Andy Shevchenko wrote:
> In a few cases the code compares 32-bit value to a SIZE_MAX derived
> constant which is much higher than that value on 64-bit platforms,
> Clang, in particular, is not happy about this
> 
> net/ceph/osdmap.c:1441:10: error: result of comparison of constant 4611686018427387891 with expression of type 'u32' (aka 'unsigned int') is always false [-Werror,-Wtautological-constant-out-of-range-compare]
>  1441 |         if (len > (SIZE_MAX - sizeof(*pg)) / sizeof(u32))
>       |             ~~~ ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> net/ceph/osdmap.c:1624:10: error: result of comparison of constant 2305843009213693945 with expression of type 'u32' (aka 'unsigned int') is always false [-Werror,-Wtautological-constant-out-of-range-compare]
>  1624 |         if (len > (SIZE_MAX - sizeof(*pg)) / (2 * sizeof(u32)))
>       |             ~~~ ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 
> fs/ceph/snap.c:377:10: error: result of comparison of constant 2305843009213693948 with expression of type 'u32' (aka 'unsigned int') is always false [-Werror,-Wtautological-constant-out-of-range-compare]
>   377 |         if (num > (SIZE_MAX - sizeof(*snapc)) / sizeof(u64))
>       |             ~~~ ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 
> Fix this by casting to size_t. Note, that possible replacement of SIZE_MAX
> by U32_MAX may lead to the behaviour changes on the corner cases.
> 
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> ---
>  net/ceph/osdmap.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/net/ceph/osdmap.c b/net/ceph/osdmap.c
> index 295098873861..8e7cb2fde6f1 100644
> --- a/net/ceph/osdmap.c
> +++ b/net/ceph/osdmap.c
> @@ -1438,7 +1438,7 @@ static struct ceph_pg_mapping *__decode_pg_temp(void **p, void *end,
>  	ceph_decode_32_safe(p, end, len, e_inval);
>  	if (len == 0 && incremental)
>  		return NULL;	/* new_pg_temp: [] to remove */
> -	if (len > (SIZE_MAX - sizeof(*pg)) / sizeof(u32))
> +	if ((size_t)len > (SIZE_MAX - sizeof(*pg)) / sizeof(u32))
>  		return ERR_PTR(-EINVAL);
>  
>  	ceph_decode_need(p, end, len * sizeof(u32), e_inval);
> @@ -1621,7 +1621,7 @@ static struct ceph_pg_mapping *__decode_pg_upmap_items(void **p, void *end,
>  	u32 len, i;

I am guessing... What if we change the declaration of len on size_t, then could
it be more clear solution here? For example, let's consider this for both cases:

size_t len, i;

Could it eliminate the issue and to make the Clang happy? Or could it introduce
another warnings/issues?

Thanks,
Slava. 

>  
>  	ceph_decode_32_safe(p, end, len, e_inval);
> -	if (len > (SIZE_MAX - sizeof(*pg)) / (2 * sizeof(u32)))
> +	if ((size_t)len > (SIZE_MAX - sizeof(*pg)) / (2 * sizeof(u32)))
>  		return ERR_PTR(-EINVAL);
>  
>  	ceph_decode_need(p, end, 2 * len * sizeof(u32), e_inval);

Re: [PATCH v1 1/1] libceph: Amend checking to fix `make W=1` build breakage

[andriy.shevchenko]

On Mon, Nov 10, 2025 at 07:28:36PM +0000, Viacheslav Dubeyko wrote:
> On Mon, 2025-11-10 at 15:46 +0100, Andy Shevchenko wrote:

...

> >  	ceph_decode_32_safe(p, end, len, e_inval);
> >  	if (len == 0 && incremental)
> >  		return NULL;	/* new_pg_temp: [] to remove */
> > -	if (len > (SIZE_MAX - sizeof(*pg)) / sizeof(u32))
> > +	if ((size_t)len > (SIZE_MAX - sizeof(*pg)) / sizeof(u32))
> >  		return ERR_PTR(-EINVAL);
> >  
> >  	ceph_decode_need(p, end, len * sizeof(u32), e_inval);

> I am guessing... What if we change the declaration of len on size_t, then could
> it be more clear solution here? For example, let's consider this for both cases:
> 
> size_t len, i;
> 
> Could it eliminate the issue and to make the Clang happy? Or could it introduce
> another warnings/issues?

Probably, but the code is pierced with the sizeof(u32) and alike, moreover
size_t is architecture-dependent type, while the set of macros in decode.h
seems to operate on the fixed-width type. That said, I prefer my way of fixing
this. But if you find another, better one, I am all ears!

*Also note, I'm not familiar with the guts of the ceph, so maybe your solution
is the best, but I want more people to confirm this.

-- 
With Best Regards,
Andy Shevchenko

RE: [PATCH v1 1/1] libceph: Amend checking to fix `make W=1` build breakage

[Viacheslav Dubeyko]

On Mon, 2025-11-10 at 21:36 +0200, andriy.shevchenko@linux.intel.com wrote:
> On Mon, Nov 10, 2025 at 07:28:36PM +0000, Viacheslav Dubeyko wrote:
> > On Mon, 2025-11-10 at 15:46 +0100, Andy Shevchenko wrote:
> 
> ...
> 
> > >  	ceph_decode_32_safe(p, end, len, e_inval);
> > >  	if (len == 0 && incremental)
> > >  		return NULL;	/* new_pg_temp: [] to remove */
> > > -	if (len > (SIZE_MAX - sizeof(*pg)) / sizeof(u32))
> > > +	if ((size_t)len > (SIZE_MAX - sizeof(*pg)) / sizeof(u32))
> > >  		return ERR_PTR(-EINVAL);
> > >  
> > >  	ceph_decode_need(p, end, len * sizeof(u32), e_inval);
> 
> > I am guessing... What if we change the declaration of len on size_t, then could
> > it be more clear solution here? For example, let's consider this for both cases:
> > 
> > size_t len, i;
> > 
> > Could it eliminate the issue and to make the Clang happy? Or could it introduce
> > another warnings/issues?
> 
> Probably, but the code is pierced with the sizeof(u32) and alike, moreover
> size_t is architecture-dependent type, while the set of macros in decode.h
> seems to operate on the fixed-width type. That said, I prefer my way of fixing
> this. But if you find another, better one, I am all ears!
> 
> *Also note, I'm not familiar with the guts of the ceph, so maybe your solution
> is the best, but I want more people to confirm this.

I think the patch looks good as it is. And we can take it. If we find the better
way
of fixing this, then we can do it anytime.

Reviewed-by: Viacheslav Dubeyko <Slava.Dubeyko@ibm.com>

Thanks,
Slava.