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From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Daniel Axtens <dja@axtens.net>
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Date: Thu, 21 Jan 2021 18:19:51 +1100
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Subject: [PATCH] disk/lvm: Don't blast past the end of the circular metadata
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buffer
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This catches at least some OOB reads, and it's possible I suppose that
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if 2 * mda_size is less than GRUB_LVM_MDA_HEADER_SIZE it might catch some
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OOB writes too (although that hasn't showed up as a crash in fuzzing yet).
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It's a bit ugly and I'd appreciate better suggestions.
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Signed-off-by: Daniel Axtens <dja@axtens.net>
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Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
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---
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grub-core/disk/lvm.c | 10 ++++++++++
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1 file changed, 10 insertions(+)
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diff --git a/grub-core/disk/lvm.c b/grub-core/disk/lvm.c
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index 0f466040a55..ec3545e164b 100644
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--- a/grub-core/disk/lvm.c
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+++ b/grub-core/disk/lvm.c
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@@ -215,6 +215,16 @@ grub_lvm_detect (grub_disk_t disk,
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if (grub_le_to_cpu64 (rlocn->offset) + grub_le_to_cpu64 (rlocn->size) >
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grub_le_to_cpu64 (mdah->size))
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{
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+ if (2 * mda_size < GRUB_LVM_MDA_HEADER_SIZE ||
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+ (grub_le_to_cpu64 (rlocn->offset) + grub_le_to_cpu64 (rlocn->size) -
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+ grub_le_to_cpu64 (mdah->size) > mda_size - GRUB_LVM_MDA_HEADER_SIZE))
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+ {
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+#ifdef GRUB_UTIL
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+ grub_util_info ("cannot copy metadata wrap in circular buffer");
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+#endif
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+ goto fail2;
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+ }
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+
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/* Metadata is circular. Copy the wrap in place. */
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grub_memcpy (metadatabuf + mda_size,
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metadatabuf + GRUB_LVM_MDA_HEADER_SIZE,
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