Reject empty paths and negative lengths, according to the DT spec v0.4:
The convention for specifying a device path is:
/node-name-1/node-name-2/node-name-N
The path to the root node is /.
This prevents the access to path[0] from ever being out-of-bounds.
Signed-off-by: Pierre-Clément Tosi <ptosi@xxxxxxxxxx>
---
v2
- allow the check to be optimized out when ASSUME_VALID_INPUT
- add test coverage for empty paths and negative size
- remove redundant part of the quote in the commit message
---
libfdt/fdt_ro.c | 3 +++
tests/path_offset.c | 6 ++++++
2 files changed, 9 insertions(+)
diff --git a/libfdt/fdt_ro.c b/libfdt/fdt_ro.c
index c4c520c..7567f52 100644
--- a/libfdt/fdt_ro.c
+++ b/libfdt/fdt_ro.c
@@ -255,6 +255,9 @@ int fdt_path_offset_namelen(const void *fdt, const char *path, int namelen)
FDT_RO_PROBE(fdt);
+ if (!can_assume(VALID_INPUT) && namelen <= 0)
+ return -FDT_ERR_BADPATH;
+
/* see if we have an alias */
if (*path != '/') {
const char *q = memchr(path, '/', end - p);
diff --git a/tests/path_offset.c b/tests/path_offset.c
index 8e657af..0193e61 100644
--- a/tests/path_offset.c
+++ b/tests/path_offset.c
@@ -48,6 +48,9 @@ static void check_path_offset(void *fdt, const char *path, int offset)
verbose_printf("Checking offset of \"%s\" is %d...\n", path, offset);
rc = fdt_path_offset(fdt, path);
+ if (rc == offset)
+ return;
+
if (rc < 0)
FAIL("fdt_path_offset(\"%s\") failed: %s",
path, fdt_strerror(rc));
@@ -102,6 +105,7 @@ int main(int argc, char *argv[])
check_path_offset(fdt, "/subnode@2/subsubnode", subsubnode2_offset2);
/* Test paths with extraneous separators */
+ check_path_offset(fdt, "", -FDT_ERR_BADPATH);
check_path_offset(fdt, "//", 0);
check_path_offset(fdt, "///", 0);
check_path_offset(fdt, "//subnode@1", subnode1_offset);
@@ -110,6 +114,8 @@ int main(int argc, char *argv[])
check_path_offset(fdt, "/subnode@2////subsubnode", subsubnode2_offset2);
/* Test fdt_path_offset_namelen() */
+ check_path_offset_namelen(fdt, "/subnode@1", -1, -FDT_ERR_BADPATH);
+ check_path_offset_namelen(fdt, "/subnode@1", 0, -FDT_ERR_BADPATH);
check_path_offset_namelen(fdt, "/subnode@1", 1, 0);
check_path_offset_namelen(fdt, "/subnode@1/subsubnode", 10, subnode1_offset);
check_path_offset_namelen(fdt, "/subnode@1/subsubnode", 11, subnode1_offset);
--
2.42.0.609.gbb76f46606-goog
--
Pierre
