On Wed, May 06, 2015 at 08:39:22PM -0400, Peter Hurley wrote: > On 05/06/2015 07:59 PM, josh@xxxxxxxxxxxxxxxx wrote: > > On Wed, May 06, 2015 at 08:44:29AM -0700, Josh Triplett wrote: > >> On Wed, May 06, 2015 at 05:08:50PM +0800, Fengguang Wu wrote: > >>> FYI, the reported bug is still not fixed in linux-next 20150506. > >> > >> This isn't the same bug. The previous one you mentioned was a userspace > >> assertion failure in libnih, likely caused because some part of upstart > >> didn't have appropriate error handling for some syscall returning > >> ENOSYS; that one wasn't an issue, since CONFIG_MULTIUSER=n is not > >> expected to boot a standard Linux distribution. > >> > >> This one, on the other hand, is a kernel panic, and does need fixing. > >> > >>> commit 2813893f8b197a14f1e1ddb04d99bce46817c84a > >>> > >>> +-----------------------------------------------------------+------------+------------+------------+ > >>> | | c79574abe2 | 2813893f8b | cbdacaf0c1 | > >>> +-----------------------------------------------------------+------------+------------+------------+ > >>> | boot_successes | 60 | 0 | 0 | > >>> | boot_failures | 0 | 22 | 1064 | > >>> | BUG:unable_to_handle_kernel | 0 | 22 | 1032 | > >>> | Oops | 0 | 22 | 1032 | > >>> | EIP_is_at_devpts_new_index | 0 | 22 | 1032 | > >>> | Kernel_panic-not_syncing:Fatal_exception | 0 | 22 | 1032 | > >>> | backtrace:do_sys_open | 0 | 22 | 1032 | > >>> | backtrace:SyS_open | 0 | 22 | 1032 | > >>> | WARNING:at_arch/x86/kernel/fpu/core.c:#fpu__clear() | 0 | 0 | 32 | > >>> | Kernel_panic-not_syncing:Attempted_to_kill_init!exitcode= | 0 | 0 | 32 | > >>> +-----------------------------------------------------------+------------+------------+------------+ > >> > >> Is this table saying the number of times the type of error in the first > >> column occurred in each commit? > >> > >> In any case, investigating. Iulia, can you look at this as well? > >> > >> I'm digging through the call stack, and I'm having a hard time seeing > >> how the CONFIG_MULTIUSER patch could affect anything here. > > > > Update: it looks like init_devpts_fs is getting ERR_PTR(-EINVAL) back > > from kern_mount and storing that in devpts_mnt; later, devpts_new_index > > pokes at devpts_mnt and explodes. > > > > So, there are two separate bugs here. On the one hand, CONFIG_MULTIUSER > > should not be causing kern_mount to fail with -EINVAL; tracking that > > down now. > > The mount failure is probably from the devpts mount options specifying > gid= for devpts nodes: > > devpts /dev/pts devpts rw,nosuid,noexec,relatime,gid=5,mode=620,ptmxmode=000 0 0 > > The relevant code is fs/devpts/inode.c:parse_mount_options(). > devpts also supports specifying the uid. > > To me, kern_mount() appropriately fails with -EINVAL, since the mount > options failed. Except that init_devpts_fs is called at module_init time, long before the actual mount syscall; it appears to be creating a kernel-internal mount, and I don't see how mount options provided by userspace much later would cause the earlier kern_mount to fail. Also, I don't see anything in parse_mount_options that should actually fail with CONFIG_MULTIUSER unset. > > On the other hand, devpts and ptmx should handle the failure > > better, without crashing; ptmx_open should have gracefully failed back > > to userspace with -ENODEV or something, since ptmx doesn't make sense > > without devpts. I'll send a patch for that too. > > Yeah, crashing is bad, but I don't think we should even be init'ing > either BSD or SysV pty drivers if there is no devpts. Can you review the patch I sent to fix the crash, and see if it looks reasonable to you? - Josh Triplett -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>