kernel
/
dtc
mirror of https://git.kernel.org/pub/scm/utils/dtc/dtc.git
1
0
Fork 0
Code Issues Projects Releases Wiki Activity

libfdt: prevent integer overflow in fdt_next_tag 

Since fdt_next_tag() in a public API function all input parameters,
including the fdt blob should not be trusted. It is possible to forge
a blob with invalid property length that will cause integer overflow
during offset calculation. To prevent that, validate the property length
read from the blob before doing calculations.

Signed-off-by: Tadeusz Struk <tadeusz.struk@linaro.org>
Message-Id: <20221005232931.3016047-1-tadeusz.struk@linaro.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
main
Tadeusz Struk 2022-10-05 16:29:30 -07:00 committed by David Gibson
parent 035fb90d53
commit 73590342fc
1 changed files with 12 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

17
libfdt/fdt.c
View File

@ -162,7 +162,7 @@ const void *fdt_offset_ptr(const void *fdt, int offset, unsigned int len)
uint32_t fdt_next_tag(const void *fdt, int startoffset, int *nextoffset)
{
const fdt32_t *tagp, *lenp;
uint32_t tag;
uint32_t tag, len, sum;
int offset = startoffset;
const char *p;

@ -188,12 +188,19 @@ uint32_t fdt_next_tag(const void *fdt, int startoffset, int *nextoffset)
lenp = fdt_offset_ptr(fdt, offset, sizeof(*lenp));
if (!can_assume(VALID_DTB) && !lenp)
return FDT_END; /* premature end */

len = fdt32_to_cpu(*lenp);
sum = len + offset;
if (!can_assume(VALID_DTB) &&
(INT_MAX <= sum || sum < (uint32_t) offset))
return FDT_END; /* premature end */

/* skip-name offset, length and value */
offset += sizeof(struct fdt_property) - FDT_TAGSIZE
+ fdt32_to_cpu(*lenp);
offset += sizeof(struct fdt_property) - FDT_TAGSIZE + len;

if (!can_assume(LATEST) &&
fdt_version(fdt) < 0x10 && fdt32_to_cpu(*lenp) >= 8 &&
((offset - fdt32_to_cpu(*lenp)) % 8) != 0)
fdt_version(fdt) < 0x10 && len >= 8 &&
((offset - len) % 8) != 0)
offset += 4;
break;