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libfdt: fdt_path_offset_namelen: Reject empty path

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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@google.com>
Message-ID: <20231010092822.qo2nxc3g47t26dqs@google.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
This commit is contained in:
Pierre-Clément Tosi 2023-10-10 10:28:22 +01:00 • committed by David Gibson
parent 79b9e326a1
commit 2283dd78ef
2 changed files with 10 additions and 1 deletions
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3
libfdt/fdt_ro.c
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@ -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);