On 08/21/18 at 03:39pm, Ard Biesheuvel wrote: > On 9 August 2018 at 11:13, Dave Young <dyoung@xxxxxxxxxx> wrote: > > On 08/09/18 at 09:33am, Mike Galbraith wrote: > >> On Thu, 2018-08-09 at 12:21 +0800, Dave Young wrote: > >> > Hi Mike, > >> > > >> > Thanks for the patch! > >> > On 08/08/18 at 04:03pm, Mike Galbraith wrote: > >> > > When booting with efi=noruntime, we call efi_runtime_map_copy() while > >> > > loading the kdump kernel, and trip over a NULL efi.memmap.map. Avoid > >> > > that and a useless allocation when the only mapping we can use (1:1) > >> > > is not available. > >> > > >> > At first glance, efi_get_runtime_map_size should return 0 in case > >> > noruntime. > >> > >> What efi does internally at unmap time is to leave everything except > >> efi.mmap.map untouched, setting it to NULL and turning off EFI_MEMMAP, > >> rendering efi.mmap.map accessors useless/unsafe without first checking > >> EFI_MEMMAP. > > > > Probably the x86 efi_init should reset nr_map to zero in case runtime is > > disabled. But let's see how Ard thinks about this and cc linux-efi. > > > > As for efi_get_runtime_map_size, it was introduced for x86 kexec use. > > for copying runtime maps, so I think it is reasonable this function > > return zero in case no runtime. > > > > I don't see the patch in the context so I cannot comment in great detail. The patch is below: https://lore.kernel.org/lkml/1533737025.4936.3.camel@xxxxxx > > In any case, it is better to decouple EFI_MEMMAP from EFI_RUNTIME > dependencies. On x86, one may imply the other, but this is not > generally the case. > > That means that efi_get_runtime_map_size() should probably check the > EFI_RUNTIME flag, and return 0 if it is cleared. Perhaps there are > other places where EFI_MEMMAP flag checks are missing, but I consider > that a separate issue. Yes, I also agree with to check EFI_RUNTIME_SERVICES. There is no point for efi_get_runtime_map_size to return a value other than 0 in case EFI_RUNTIME_SERVICES is not set ie. via efi=noruntime Is below patch acceptable? The copy function can be changed to return an error in case map size == 0, but that can be done later along with the caller size cleanups in kexec code --------------------------------------------------------------------------- efi: check EFI_RUNTIME_SERVICES flag in runtime map copying code Mike reported a kexec_file_load NULL pointer dereference bug like below: [ 5.878262] BUG: unable to handle kernel NULL pointer dereference at 0000000000000000 [ 5.879868] PGD 800000013c1f1067 P4D 800000013c1f1067 PUD 13aea7067 PMD 0 [ 5.881225] Oops: 0000 [#1] SMP PTI [ 5.882068] Modules linked in: [ 5.882851] CPU: 0 PID: 394 Comm: kexec Kdump: loaded Not tainted 4.17.0-rc2+ #648 [ 5.884333] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015 [ 5.885843] RIP: 0010:memcpy_erms+0x6/0x10 [ 5.886789] RSP: 0018:ffffc9000058bd00 EFLAGS: 00010246 [ 5.887899] RAX: ffff880138e050b0 RBX: 00000000000980b0 RCX: 0000000000000ba0 [ 5.889304] RDX: 0000000000000ba0 RSI: 0000000000000000 RDI: ffff880138e050b0 [ 5.890977] RBP: ffff880138e04000 R08: 0000000000000017 R09: 0000000000000002 [ 5.892524] R10: 0000000000099000 R11: 00000000000052d0 R12: 0000000039400200 [ 5.893967] R13: ffff880138e05000 R14: 0000000000000ba0 R15: ffffc90000a4d000 [ 5.895378] FS: 00007f167c9e6740(0000) GS:ffff88013fc00000(0000) knlGS:0000000000000000 [ 5.896953] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 5.898143] CR2: 0000000000000000 CR3: 000000013c3ec002 CR4: 00000000001606f0 [ 5.899542] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 5.900962] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 5.902552] Call Trace: [ 5.903267] efi_runtime_map_copy+0x28/0x30 [ 5.904956] bzImage64_load+0x59d/0x736 [ 5.906881] ? arch_kexec_kernel_image_load+0x6d/0x70 [ 5.908243] ? __se_sys_kexec_file_load+0x24b/0x750 [ 5.909352] ? _cond_resched+0x19/0x30 [ 5.910286] ? do_syscall_64+0x65/0x180 [ 5.911229] ? entry_SYSCALL_64_after_hwframe+0x44/0xa9 [ 5.912365] Code: 90 90 90 90 90 eb 1e 0f 1f 00 48 89 f8 48 89 d1 48 c1 e9 03 83 e2 07 f3 48 a5 89 d1 f3 a4 c3 66 0f 1f 44 00 00 48 89 f8 48 89 d1 <f3> a4 c3 0f 1f 80 00 00 00 00 48 89 f8 48 83 fa 20 72 7e 40 38 [ 5.916235] RIP: memcpy_erms+0x6/0x10 RSP: ffffc9000058bd00 [ 5.917507] CR2: 0000000000000000 [ 5.918762] ---[ end trace 5cf4c4b3b93d7fdd ]--- Changing efi_get_runtime_map_size to return 0 in case runtime is disabled. Also moving to check EFI_RUNTIME_SERVICES in efi_runtime_map_copy Signed-off-by: Dave Young <dyoung@xxxxxxxxxx> --- drivers/firmware/efi/runtime-map.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) --- linux-x86.orig/drivers/firmware/efi/runtime-map.c +++ linux-x86/drivers/firmware/efi/runtime-map.c @@ -138,12 +138,18 @@ add_sysfs_runtime_map_entry(struct kobje int efi_get_runtime_map_size(void) { - return efi.memmap.nr_map * efi.memmap.desc_size; + if (efi_enabled(EFI_RUNTIME_SERVICES)) + return efi.memmap.nr_map * efi.memmap.desc_size; + + return 0; } int efi_get_runtime_map_desc_size(void) { - return efi.memmap.desc_size; + if (efi_enabled(EFI_RUNTIME_SERVICES)) + return efi.memmap.desc_size; + + return 0; } int efi_runtime_map_copy(void *buf, size_t bufsz) @@ -163,7 +169,7 @@ int __init efi_runtime_map_init(struct k struct efi_runtime_map_entry *entry; efi_memory_desc_t *md; - if (!efi_enabled(EFI_MEMMAP)) + if (!efi_enabled(EFI_RUNTIME_SERVICES)) return 0; map_entries = kcalloc(efi.memmap.nr_map, sizeof(entry), GFP_KERNEL); _______________________________________________ kexec mailing list kexec@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/kexec
