Addressed a specific overflow issue in the eth_dev_adjust_nb_desc()
function where the uint16_t variable nb_desc would overflow when its
value was greater than (2^16 - nb_align). This overflow caused nb_desc
to incorrectly wrap around between 0 and nb_align-1, leading to the
function setting nb_desc to nb_min instead of the expected nb_max.
The resolution involves upcasting nb_desc to a uint32_t before the
RTE_ALIGN_CEIL macro is applied. This change ensures that the subsequent
call to RTE_ALIGN_FLOOR(nb_desc + (nb_align - 1), nb_align) does not
result in an overflow, as it would when nb_desc is a uint16_t. By using
a uint32_t for these operations, the correct behavior is maintained
without the risk of overflow.
Fixes: 0f67fc3baeb9 ("ethdev: add function to adjust number of descriptors")
Signed-off-by: Niall Meade <niall.me...@intel.com>
---
.mailmap | 1 +
lib/ethdev/rte_ethdev.c | 12 +++++++++---
2 files changed, 10 insertions(+), 3 deletions(-)
diff --git a/.mailmap b/.mailmap
index 4a508bafad..c1941e78bb 100644
--- a/.mailmap
+++ b/.mailmap
@@ -1053,6 +1053,7 @@ Nelson Escobar <neesc...@cisco.com>
Nemanja Marjanovic <nemanja.marjano...@intel.com>
Netanel Belgazal <neta...@amazon.com>
Netanel Gonen <netan...@mellanox.com>
+Niall Meade <niall.me...@intel.com>
Niall Power <niall.po...@intel.com>
Nicholas Pratte <npra...@iol.unh.edu>
Nick Connolly <nick.conno...@arm.com> <nick.conno...@mayadata.io>
diff --git a/lib/ethdev/rte_ethdev.c b/lib/ethdev/rte_ethdev.c
index f1c658f49e..f978283edf 100644
--- a/lib/ethdev/rte_ethdev.c
+++ b/lib/ethdev/rte_ethdev.c
@@ -6577,13 +6577,19 @@ static void
eth_dev_adjust_nb_desc(uint16_t *nb_desc,
const struct rte_eth_desc_lim *desc_lim)
{
+ /* Upcast to uint32 to avoid potential overflow with RTE_ALIGN_CEIL().
*/
+ uint32_t nb_desc_32 = *nb_desc;
+
if (desc_lim->nb_align != 0)
- *nb_desc = RTE_ALIGN_CEIL(*nb_desc, desc_lim->nb_align);
+ nb_desc_32 = RTE_ALIGN_CEIL(nb_desc_32, desc_lim->nb_align);
if (desc_lim->nb_max != 0)
- *nb_desc = RTE_MIN(*nb_desc, desc_lim->nb_max);
+ nb_desc_32 = RTE_MIN(nb_desc_32, desc_lim->nb_max);
+
+ nb_desc_32 = RTE_MAX(nb_desc_32, desc_lim->nb_min);
- *nb_desc = RTE_MAX(*nb_desc, desc_lim->nb_min);
+ /* Assign clipped u32 back to u16. */
+ *nb_desc = nb_desc_32;
}
int
--
2.34.1
--------------------------------------------------------------
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