Re: [PATCH 2/9] libceph: avoid clang out-of-range warning

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On 3/28/24 22:30, Arnd Bergmann wrote:
From: Arnd Bergmann <arnd@xxxxxxxx>

clang-14 points out that on 64-bit architectures, a u32
is never larger than constant based on SIZE_MAX:

net/ceph/osdmap.c:1425:10: 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]
         if (len > (SIZE_MAX - sizeof(*pg)) / sizeof(u32))
             ~~~ ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
net/ceph/osdmap.c:1608:10: 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]
         if (len > (SIZE_MAX - sizeof(*pg)) / (2 * sizeof(u32)))
             ~~~ ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The code is correct anyway, so just shut up that warning.

Fixes: 6f428df47dae ("libceph: pg_upmap[_items] infrastructure")
Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
---
  fs/ceph/snap.c    | 2 +-
  net/ceph/osdmap.c | 4 ++--
  2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/fs/ceph/snap.c b/fs/ceph/snap.c
index c65f2b202b2b..521507ea8260 100644
--- a/fs/ceph/snap.c
+++ b/fs/ceph/snap.c
@@ -374,7 +374,7 @@ static int build_snap_context(struct ceph_mds_client *mdsc,
/* alloc new snap context */
  	err = -ENOMEM;
-	if (num > (SIZE_MAX - sizeof(*snapc)) / sizeof(u64))
+	if ((size_t)num > (SIZE_MAX - sizeof(*snapc)) / sizeof(u64))
  		goto fail;
  	snapc = ceph_create_snap_context(num, GFP_NOFS);
  	if (!snapc)
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);


Reviewed-by: Xiubo Li <xiubli@xxxxxxxxxx>

Thanks

- Xiubo






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