On 03/18/2013 10:51 PM, Matt Fleming wrote: > How does everyone feel about this version? Lingzhu, if I could get a > Tested-by for this version that would be great. This, plus some other > patches, are sitting on the 'urgent' branch. > > --- > > From 544a6c06479e4ea4e7acc7eea589a82f0ff9aa6d Mon Sep 17 00:00:00 2001 > From: Matt Fleming <matt.fleming@xxxxxxxxx> > Date: Thu, 7 Mar 2013 11:59:14 +0000 > Subject: [PATCH] efivars: Handle duplicate names from get_next_variable() > > Some firmware exhibits a bug where the same VariableName and > VendorGuid values are returned on multiple invocations of > GetNextVariableName(). See, > > https://bugzilla.kernel.org/show_bug.cgi?id=47631 > > As a consequence of such a bug, Andre reports hitting the following > WARN_ON() in the sysfs code after updating the BIOS on his, "Gigabyte > Technology Co., Ltd. To be filled by O.E.M./Z77X-UD3H, BIOS F19e > 11/21/2012)" machine, > > [ 0.581554] EFI Variables Facility v0.08 2004-May-17 > [ 0.584914] ------------[ cut here ]------------ > [ 0.585639] WARNING: at /home/andre/linux/fs/sysfs/dir.c:536 sysfs_add_one+0xd4/0x100() > [ 0.586381] Hardware name: To be filled by O.E.M. > [ 0.587123] sysfs: cannot create duplicate filename '/firmware/efi/vars/SbAslBufferPtrVar-01f33c25-764d-43ea-aeea-6b5a41f3f3e8' > [ 0.588694] Modules linked in: > [ 0.589484] Pid: 1, comm: swapper/0 Not tainted 3.8.0+ #7 > [ 0.590280] Call Trace: > [ 0.591066] [<ffffffff81208954>] ? sysfs_add_one+0xd4/0x100 > [ 0.591861] [<ffffffff810587bf>] warn_slowpath_common+0x7f/0xc0 > [ 0.592650] [<ffffffff810588bc>] warn_slowpath_fmt+0x4c/0x50 > [ 0.593429] [<ffffffff8134dd85>] ? strlcat+0x65/0x80 > [ 0.594203] [<ffffffff81208954>] sysfs_add_one+0xd4/0x100 > [ 0.594979] [<ffffffff81208b78>] create_dir+0x78/0xd0 > [ 0.595753] [<ffffffff81208ec6>] sysfs_create_dir+0x86/0xe0 > [ 0.596532] [<ffffffff81347e4c>] kobject_add_internal+0x9c/0x220 > [ 0.597310] [<ffffffff81348307>] kobject_init_and_add+0x67/0x90 > [ 0.598083] [<ffffffff81584a71>] ? efivar_create_sysfs_entry+0x61/0x1c0 > [ 0.598859] [<ffffffff81584b2b>] efivar_create_sysfs_entry+0x11b/0x1c0 > [ 0.599631] [<ffffffff8158517e>] register_efivars+0xde/0x420 > [ 0.600395] [<ffffffff81d430a7>] ? edd_init+0x2f5/0x2f5 > [ 0.601150] [<ffffffff81d4315f>] efivars_init+0xb8/0x104 > [ 0.601903] [<ffffffff8100215a>] do_one_initcall+0x12a/0x180 > [ 0.602659] [<ffffffff81d05d80>] kernel_init_freeable+0x13e/0x1c6 > [ 0.603418] [<ffffffff81d05586>] ? loglevel+0x31/0x31 > [ 0.604183] [<ffffffff816a6530>] ? rest_init+0x80/0x80 > [ 0.604936] [<ffffffff816a653e>] kernel_init+0xe/0xf0 > [ 0.605681] [<ffffffff816ce7ec>] ret_from_fork+0x7c/0xb0 > [ 0.606414] [<ffffffff816a6530>] ? rest_init+0x80/0x80 > [ 0.607143] ---[ end trace 1609741ab737eb29 ]--- > > There's not much we can do to work around and keep traversing the > variable list once we hit this firmware bug. Our only solution is to > terminate the loop because, as Lingzhu reports, some machines get > stuck when they encounter duplicate names, > > > I had an IBM System x3100 M4 and x3850 X5 on which kernel would > > get stuck in infinite loop creating duplicate sysfs files because, > > for some reason, there are several duplicate boot entries in nvram > > getting GetNextVariableName into a circle of iteration (with > > period > 2). > > Also disable the workqueue, as efivar_update_sysfs_entries() uses > GetNextVariableName() to figure out which variables have been created > since the last iteration. That algorithm isn't going to work if > GetNextVariableName() returns duplicates. Note that we don't disable > EFI variable creation completely on the affected machines, it's just > that any pstore dump-* files won't appear in sysfs until the next > boot. > > Reported-by: Andre Heider <a.heider@xxxxxxxxx> > Reported-by: Lingzhu Xiang <lxiang@xxxxxxxxxx> > Cc: Seiji Aguchi <seiji.aguchi@xxxxxxx> > Cc: <stable@xxxxxxxxxxxxxxx> > Signed-off-by: Matt Fleming <matt.fleming@xxxxxxxxx> Tested-by: Lingzhu Xiang <lxiang@xxxxxxxxxx> Reproduced with 3.9-rc3 in QEMU/OVMF. The kernel gets stuck in a loop. Verified with 3.9-rc3 with this patch. The kernel survives. efivarfs continues working, though some variables won't show up, as expected. [ 2.033855] efivars: duplicate variable: Boot0001-8be4df61-93ca-11d2-aa0d-00e098032b8c This patch has no real impact for users with normal firmware as tested before on a Windows 8 logo desktop. For the record, here is how I create duplicate variables in QEMU/OVMF: OVMF EmuVariableFvbRuntimeDxe emulates nvram with a reserved area of memory (ReserveEmuVariableNvStore). But there seems to be some layers of cache above this, so directly writing a new duplicate variable here won't make a difference. I ended up writing an EFI app to scan the entire memory and replace all L"Boot0004" with L"Boot0001", which seemed to actually break things (e.g. dmpstore will get stuck). -- To unsubscribe from this list: send the line "unsubscribe linux-efi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
