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libfdt: Safer access to memory reservations

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fdt_num_mem_rsv() and fdt_get_mem_rsv() currently don't sanity check their
parameters, or the memory reserve section offset in the header.  That means
that on a corrupted blob they could access outside of the range of memory
that they should.

This improves their safety checking, meaning they shouldn't access outside
the blob's bounds, even if its contents are badly corrupted.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Tested-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Reviewed-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Reviewed-by: Simon Glass <sjg@chromium.org>
This commit is contained in:
David Gibson 2018-03-09 23:28:56 +11:00
parent 719d582e98
commit d5db5382c5
7 changed files with 114 additions and 7 deletions
Download patch file Download diff file Expand all files Collapse all files

33
libfdt/fdt_ro.c
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@ -170,21 +170,42 @@ uint32_t fdt_get_max_phandle(const void *fdt)
return 0;
}
static const struct fdt_reserve_entry *fdt_mem_rsv(const void *fdt, int n)
{
int offset = n * sizeof(struct fdt_reserve_entry);
int absoffset = fdt_off_mem_rsvmap(fdt) + offset;
if (absoffset < fdt_off_mem_rsvmap(fdt))
return NULL;
if (absoffset > fdt_totalsize(fdt) - sizeof(struct fdt_reserve_entry))
return NULL;
return fdt_mem_rsv_(fdt, n);
}
int fdt_get_mem_rsv(const void *fdt, int n, uint64_t *address, uint64_t *size)
{
const struct fdt_reserve_entry *re;
FDT_RO_PROBE(fdt);
*address = fdt64_to_cpu(fdt_mem_rsv_(fdt, n)->address);
*size = fdt64_to_cpu(fdt_mem_rsv_(fdt, n)->size);
re = fdt_mem_rsv(fdt, n);
if (!re)
return -FDT_ERR_BADOFFSET;
*address = fdt64_to_cpu(re->address);
*size = fdt64_to_cpu(re->size);
return 0;
}
int fdt_num_mem_rsv(const void *fdt)
{
int i = 0;
int i;
const struct fdt_reserve_entry *re;
while (fdt64_to_cpu(fdt_mem_rsv_(fdt, i)->size) != 0)
i++;
return i;
for (i = 0; (re = fdt_mem_rsv(fdt, i)) != NULL; i++) {
if (fdt64_to_cpu(re->size) == 0)
return i;
}
return -FDT_ERR_TRUNCATED;
}
static int nextprop_(const void *fdt, int offset)