On 05/07/2015 11:56 AM, josh@xxxxxxxxxxxxxxxx wrote: > 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. Yeah, I realized that later; that the userspace mount is really a rebind to that initial root kernel mount. > Also, I don't see anything in parse_mount_options that should actually > fail with CONFIG_MULTIUSER unset. I didn't look deeper than that, but it seemed likely that it stemmed from that. Maybe it's related to CONFIG_DEVPTS_MULTIPLE_INSTANCES (documented in Documentation/fs/devpts.txt) and FS_USERNS_MOUNT? >>> 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? On my todo list for today. Regards, Peter Hurley -- 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>