On Thu, Oct 16, 2025 at 8:41 PM Ben Copeland ben.copeland@linaro.org wrote:

The overcommit test uses sum_total, the sum (memory and swap) to test the overcommit settings.

This fixes two problems on 32-bit systems. The first is seen with a integer overflow can occur when calculating sum_total * 2, if the sum_total is larger than 2GB. The second is limited virtual address space (2-3GB) means the test can fail from address space exhaustion before overcommit has been tested.

Now the test runs correctly on low-memory 32-bit systems while avoiding both the overflow bug and virtual address space issues.

Acked-by: Arnd Bergmann arnd@arndb.de Reviewed-by: Petr Vorel pvorel@suse.cz Signed-off-by: Ben Copeland ben.copeland@linaro.org

Reviewed-by: Li Wang liwang@redhat.com

---

.../kernel/mem/tunable/overcommit_memory.c | 31 ++++++++++++++----- 1 file changed, 24 insertions(+), 7 deletions(-)

diff --git a/testcases/kernel/mem/tunable/overcommit_memory.c b/testcases/kernel/mem/tunable/overcommit_memory.c index 9b2cb479d..d4faaeee0 100644 --- a/testcases/kernel/mem/tunable/overcommit_memory.c +++ b/testcases/kernel/mem/tunable/overcommit_memory.c @@ -131,24 +131,41 @@ static void overcommit_memory_test(void) TST_SYS_CONF_LONG_SET(OVERCOMMIT_MEMORY, 2, 1);

    update_mem_commit();

•   alloc_and_check(commit_left * 2, EXPECT_FAIL);
  

•   alloc_and_check(commit_limit + total_batch_size, EXPECT_FAIL);
  

•   update_mem_commit();
  

•   alloc_and_check(commit_left / 2, EXPECT_PASS);
  

•   /* Skip tests that would overflow or exceed 32-bit address space */
  

•   if (tst_kernel_bits() == 64 || (unsigned long)commit_left <=
  

TST_GB / TST_KB) {

•           alloc_and_check(commit_left * 2, EXPECT_FAIL);
  

•           alloc_and_check(commit_limit + total_batch_size,
  

EXPECT_FAIL);

•           update_mem_commit();
  

•           alloc_and_check(commit_left / 2, EXPECT_PASS);
  

•   } else {
  

•           tst_res(TCONF, "Skipping large allocation tests due to
  

address space limits");

•   }
  
    /* start to test overcommit_memory=0 */
    TST_SYS_CONF_LONG_SET(OVERCOMMIT_MEMORY, 0, 1);
  
    update_mem();
    alloc_and_check(free_total / 2, EXPECT_PASS);
  

•   alloc_and_check(sum_total * 2, EXPECT_FAIL);
  

•   /* Skip if sum_total * 2 would exceed address space.
  

•    * On 32-bit, skip when sum_total > ULONG_MAX/4 (~1GB).
  

•    * Most 32-bit systems with <=1GB RAM can map 2x that in 3GB vaddr
  

space.

•    * Systems with 2GB+ RAM likely cannot fit allocations in vaddr
  

space. */

•   if (tst_kernel_bits() == 64 || (unsigned long)sum_total <= TST_GB
  

/ TST_KB) {

•           alloc_and_check(sum_total * 2, EXPECT_FAIL);
  

•   } else {
  

•           tst_res(TCONF, "Skipping large allocation test due to
  

address space limits");

•   }
  
    /* start to test overcommit_memory=1 */
    TST_SYS_CONF_LONG_SET(OVERCOMMIT_MEMORY, 1, 1);
  
    alloc_and_check(sum_total / 2, EXPECT_PASS);
  

•   alloc_and_check(sum_total, EXPECT_PASS);
  

•   alloc_and_check(sum_total * 2, EXPECT_PASS);
  

•   if (tst_kernel_bits() == 64 || (unsigned long)sum_total <= TST_GB
  

/ TST_KB) {

•           alloc_and_check(sum_total, EXPECT_PASS);
  

•           alloc_and_check(sum_total * 2, EXPECT_PASS);
  

•   } else {
  

•           tst_res(TCONF, "Skipping large allocation tests due to
  

address space limits");

•   }
  
  

}

-- 2.51.0

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