Messages in this thread | | | Date | Fri, 19 May 2023 10:36:59 -0400 | From | "Liam R. Howlett" <> | Subject | Re: LTP: shmget02 fails on compat mode - 64-bit kernel and 32-bit userspace |
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* 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/kernel/syscalls/ipc/shmget/shmget02.c#LL59C1-L59C61 > > 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
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