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loader/multiboot_elfxx: Check program header offset doesn't exceed constraints

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In grub-core/loader/multiboot_elfxx.c, we need to make sure that the program
header offset is less than the file size along with the MULTIBOOT_SEARCH
constant. We can do so by setting the variable phlimit to the minimum value of
the two limits and check it each time we change program header index to insure
that the program header offset isn't outside of the limits.

Fixes: CID 314029
Fixes: CID 314038

Signed-off-by: Alec Brown <alec.r.brown@oracle.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
This commit is contained in:
Alec Brown 2023-05-22 16:52:48 -04:00 committed by Daniel Kiper
parent c8cf8272f4
commit 78bc9a9b2b
1 changed files with 3 additions and 1 deletions
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4
grub-core/loader/multiboot_elfxx.c
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@ -70,6 +70,7 @@ CONCAT(grub_multiboot_load_elf, XX) (mbi_load_data_t *mld)
grub_uint32_t load_offset = 0, load_size = 0;
Elf_Shnum shnum;
Elf_Word shstrndx, phnum;
grub_off_t phlimit;
unsigned int i;
void *source = NULL;
@ -100,7 +101,8 @@ CONCAT(grub_multiboot_load_elf, XX) (mbi_load_data_t *mld)
return err;
/* FIXME: Should we support program headers at strange locations? */
if (ehdr->e_phoff + phnum * ehdr->e_phentsize > MULTIBOOT_SEARCH)
phlimit = grub_min (MULTIBOOT_SEARCH, grub_file_size (mld->file));
if ((grub_off_t) ehdr->e_phoff + phnum * ehdr->e_phentsize > phlimit)
return grub_error (GRUB_ERR_BAD_OS, "program header at a too high offset");
phdr_base = (char *) mld->buffer + ehdr->e_phoff;