From: "Pierre-Clément Tosi" <ptosi@google.com>
To: David Gibson <david@gibson.dropbear.id.au>
Cc: devicetree-compiler@vger.kernel.org,
Mike McTernan <mikemcternan@google.com>,
Simon Glass <sjg@chromium.org>
Subject: [PATCH] libfdt: fdt_get_alias_namelen: Validate aliases
Date: Sat, 7 Oct 2023 12:07:10 +0100 [thread overview]
Message-ID: <20231007110710.i2oj24oirdtyt5m4@google.com> (raw)
Ensure that the alias found is valid i.e.
An alias value is a device path and is encoded as a string.
The value represents the full path to a node, ...
This protects against a stack overflow (fdt_path_offset_namelen() calls
fdt_get_alias_namelen() then fdt_path_offset(alias), ...) when /aliases
has an empty property with an empty name.
Co-developed-by: Mike McTernan <mikemcternan@google.com>
Signed-off-by: Pierre-Clément Tosi <ptosi@google.com>
---
libfdt/fdt_ro.c | 11 ++++++++++-
tests/aliases.dts | 3 +++
tests/get_alias.c | 12 +++++++++++-
3 files changed, 24 insertions(+), 2 deletions(-)
diff --git a/libfdt/fdt_ro.c b/libfdt/fdt_ro.c
index c4c520c..bda5c0d 100644
--- a/libfdt/fdt_ro.c
+++ b/libfdt/fdt_ro.c
@@ -537,7 +537,16 @@ static const void *fdt_path_getprop_namelen(const void *fdt, const char *path,
const char *fdt_get_alias_namelen(const void *fdt,
const char *name, int namelen)
{
- return fdt_path_getprop_namelen(fdt, "/aliases", name, namelen, NULL);
+ int len;
+ const char *alias;
+
+ alias = fdt_path_getprop_namelen(fdt, "/aliases", name, namelen, &len);
+
+ if (!can_assume(VALID_DTB) &&
+ !(len > 0 && alias && memchr(alias, '\0', len) && *alias == '/'))
+ return NULL;
+
+ return alias;
}
const char *fdt_get_alias(const void *fdt, const char *name)
diff --git a/tests/aliases.dts b/tests/aliases.dts
index 853479a..8820974 100644
--- a/tests/aliases.dts
+++ b/tests/aliases.dts
@@ -8,6 +8,9 @@
s1 = &sub1;
ss1 = &subsub1;
sss1 = &subsubsub1;
+ badpath = "wrong";
+ badpathlong = "wrong/with/parts";
+ empty = "";
};
sub1: subnode@1 {
diff --git a/tests/get_alias.c b/tests/get_alias.c
index fb2c38c..4f3f6fd 100644
--- a/tests/get_alias.c
+++ b/tests/get_alias.c
@@ -21,9 +21,16 @@ static void check_alias(void *fdt, const char *path, const char *alias)
aliaspath = fdt_get_alias(fdt, alias);
- if (path && !aliaspath)
+ if (!path && !aliaspath)
+ return;
+
+ if (!aliaspath)
FAIL("fdt_get_alias(%s) failed\n", alias);
+ if (!path)
+ FAIL("fdt_get_alias(%s) returned %s instead of NULL",
+ alias, aliaspath);
+
if (strcmp(aliaspath, path) != 0)
FAIL("fdt_get_alias(%s) returned %s instead of %s\n",
alias, aliaspath, path);
@@ -36,6 +43,9 @@ int main(int argc, char *argv[])
test_init(argc, argv);
fdt = load_blob_arg(argc, argv);
+ check_alias(fdt, NULL, "badpath");
+ check_alias(fdt, NULL, "badpathlong");
+ check_alias(fdt, NULL, "empty");
check_alias(fdt, "/subnode@1", "s1");
check_alias(fdt, "/subnode@1/subsubnode", "ss1");
check_alias(fdt, "/subnode@1/subsubnode/subsubsubnode", "sss1");
--
2.42.0.609.gbb76f46606-goog
--
Pierre
next reply other threads:[~2023-10-07 11:07 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-10-07 11:07 Pierre-Clément Tosi [this message]
2023-10-08 7:13 ` [PATCH] libfdt: fdt_get_alias_namelen: Validate aliases David Gibson
2023-10-09 14:09 ` Pierre-Clément Tosi
2023-10-10 4:04 ` David Gibson
2023-10-10 14:18 ` Mike McTernan
2023-10-11 0:36 ` David Gibson
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