From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001 From: Daniel Axtens Date: Thu, 21 Jan 2021 18:19:51 +1100 Subject: [PATCH] disk/lvm: Don't blast past the end of the circular metadata buffer This catches at least some OOB reads, and it's possible I suppose that if 2 * mda_size is less than GRUB_LVM_MDA_HEADER_SIZE it might catch some OOB writes too (although that hasn't showed up as a crash in fuzzing yet). It's a bit ugly and I'd appreciate better suggestions. Signed-off-by: Daniel Axtens Reviewed-by: Daniel Kiper --- grub-core/disk/lvm.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/grub-core/disk/lvm.c b/grub-core/disk/lvm.c index 0f466040a..ec3545e16 100644 --- a/grub-core/disk/lvm.c +++ b/grub-core/disk/lvm.c @@ -215,6 +215,16 @@ grub_lvm_detect (grub_disk_t disk, if (grub_le_to_cpu64 (rlocn->offset) + grub_le_to_cpu64 (rlocn->size) > grub_le_to_cpu64 (mdah->size)) { + if (2 * mda_size < GRUB_LVM_MDA_HEADER_SIZE || + (grub_le_to_cpu64 (rlocn->offset) + grub_le_to_cpu64 (rlocn->size) - + grub_le_to_cpu64 (mdah->size) > mda_size - GRUB_LVM_MDA_HEADER_SIZE)) + { +#ifdef GRUB_UTIL + grub_util_info ("cannot copy metadata wrap in circular buffer"); +#endif + goto fail2; + } + /* Metadata is circular. Copy the wrap in place. */ grub_memcpy (metadatabuf + mda_size, metadatabuf + GRUB_LVM_MDA_HEADER_SIZE,