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| author | Tadeusz Struk <tadeusz.struk@linaro.org> | 2022-10-05 16:29:30 -0700 |
|---|---|---|
| committer | David Gibson <david@gibson.dropbear.id.au> | 2022-10-12 10:49:36 +1100 |
| commit | 73590342fc85ca207ca1e6cbc110179873a96962 (patch) | |
| tree | 90348d0224d82b5802ee13f7932dc93afb32b884 | |
| parent | 035fb90d537540a5fbf24569df74aec667704e4d (diff) | |
| download | device-tree-compiler-73590342fc85ca207ca1e6cbc110179873a96962.tar.gz | |
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>
| -rw-r--r-- | libfdt/fdt.c | 17 |
1 files changed, 12 insertions, 5 deletions
diff --git a/libfdt/fdt.c b/libfdt/fdt.c index 90a39e8..20c6415 100644 --- a/libfdt/fdt.c +++ b/libfdt/fdt.c @@ -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; |