* Arnd Bergmann arnd@arndb.de [230519 06:57]:
On Fri, May 19, 2023, at 11:17, Naresh Kamboju wrote:
LTP running on compat mode where the tests run on 64-bit kernel and 32-bit userspace are noticed on a list of failures.
Is this new?
What would be the best way to handle this rare combination of failures ?
- arm64: juno-r2-compat, qemu_arm64-compat and qemu_x86_64-compat
- shmget02
Reported-by: Linux Kernel Functional Testing lkft@linaro.org
tst_hugepage.c:83: TINFO: 0 hugepage(s) reserved tst_test.c:1558: TINFO: Timeout per run is 0h 02m 30s tst_kconfig.c:87: TINFO: Parsing kernel config '/proc/config.gz' shmget02.c:95: TPASS: shmget(1644199826, 2048, 1024) : ENOENT (2) shmget02.c:95: TPASS: shmget(1627422610, 2048, 1536) : EEXIST (17) <4>[ 84.678150] __vm_enough_memory: pid: 513, comm: shmget02, not enough memory for the allocation shmget02.c:95: TPASS: shmget(1644199826, 0, 1536) : EINVAL (22) shmget02.c:95: TFAIL: shmget(1644199826, 4278190080, 1536) expected EINVAL: ENOMEM (12)
Adding Liam Howlett, Davidlohr Bueso and Manfred Spraul to Cc, they have worked on the shm code in the past few years.
There was an issue with returning ENOMEM on 32bit which may be causing this failure - if it's new.
This is the line
{&shmkey1, SHMMAX + 1, IPC_CREAT | IPC_EXCL, 0, 0, EINVAL},
from
https://github.com/linux-test-project/ltp/blob/04e8f2f4fd949/testcases/kerne...
right?
I think this is a result of SHMMAX being defined as #define SHMMAX (ULONG_MAX - (1UL << 24)), so the kernel would likely use a large 64-bit value here, while the 32-bit user space uses a much smaller limit.
The expected return code likely comes from
static int newseg(struct ipc_namespace *ns, struct ipc_params *params) { ... if (size < SHMMIN || size > ns->shm_ctlmax) return -EINVAL; but if ns->shm_ctlmax is probably set to the 64-bit value here. It would then trigger the accounting limit in __shmem_file_setup():
if (shmem_acct_size(flags, size)) return ERR_PTR(-ENOMEM);My feeling is that the kernel in this case works as expected, and I wouldn't see this as a bug. On the other hand, this can probably be addressed in the kernel by adding a check for compat tasks like
--- a/ipc/shm.c +++ b/ipc/shm.c @@ -714,7 +714,8 @@ static int newseg(struct ipc_namespace *ns, struct ipc_params *params) char name[13]; vm_flags_t acctflag = 0;
if (size < SHMMIN || size > ns->shm_ctlmax)
if (size < SHMMIN || size > ns->shm_ctlmax ||in_compat_syscall() && size > COMPAT_SHMMAX)) return -EINVAL;if (numpages << PAGE_SHIFT < size)
Arnd