57 lines
2.0 KiB
Diff
57 lines
2.0 KiB
Diff
From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Alec Brown <alec.r.brown@oracle.com>
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Date: Wed, 5 Feb 2025 22:04:08 +0000
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Subject: [PATCH] loader/i386/bsd: Use safe math to avoid underflow
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The operation kern_end - kern_start may underflow when we input it into
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grub_relocator_alloc_chunk_addr() call. To avoid this we can use safe
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math for this subtraction.
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Fixes: CID 73845
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Signed-off-by: Alec Brown <alec.r.brown@oracle.com>
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Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
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---
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grub-core/loader/i386/bsd.c | 14 ++++++++++----
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1 file changed, 10 insertions(+), 4 deletions(-)
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diff --git a/grub-core/loader/i386/bsd.c b/grub-core/loader/i386/bsd.c
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index b5ab848ee..ff1658503 100644
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--- a/grub-core/loader/i386/bsd.c
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+++ b/grub-core/loader/i386/bsd.c
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@@ -1341,6 +1341,7 @@ static grub_err_t
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grub_bsd_load_elf (grub_elf_t elf, const char *filename)
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{
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grub_err_t err;
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+ grub_size_t sz;
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kern_end = 0;
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kern_start = ~0;
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@@ -1371,8 +1372,11 @@ grub_bsd_load_elf (grub_elf_t elf, const char *filename)
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if (grub_errno)
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return grub_errno;
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- err = grub_relocator_alloc_chunk_addr (relocator, &ch,
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- kern_start, kern_end - kern_start);
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+
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+ if (grub_sub (kern_end, kern_start, &sz))
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+ return grub_error (GRUB_ERR_OUT_OF_RANGE, "underflow detected while determining size of kernel for relocator");
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+
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+ err = grub_relocator_alloc_chunk_addr (relocator, &ch, kern_start, sz);
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if (err)
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return err;
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@@ -1432,8 +1436,10 @@ grub_bsd_load_elf (grub_elf_t elf, const char *filename)
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{
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grub_relocator_chunk_t ch;
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- err = grub_relocator_alloc_chunk_addr (relocator, &ch, kern_start,
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- kern_end - kern_start);
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+ if (grub_sub (kern_end, kern_start, &sz))
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+ return grub_error (GRUB_ERR_OUT_OF_RANGE, "underflow detected while determining size of kernel for relocator");
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+
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+ err = grub_relocator_alloc_chunk_addr (relocator, &ch, kern_start, sz);
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if (err)
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return err;
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kern_chunk_src = get_virtual_current_address (ch);
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