From e13c8162656665f9ec1c76a033cae5b011b8c658 Mon Sep 17 00:00:00 2001

From: James Carter <jwcart2@gmail.com>

Date: Thu, 8 Apr 2021 13:24:29 -0400

Subject: [PATCH] libsepol/cil: Fix out-of-bound read of file context pattern

 ending with "\"

Based on patch by Nicolas Iooss, who writes:

  OSS-Fuzz found a Heap-buffer-overflow in the CIL compiler when trying

  to compile the following policy:

    (sid SID)

    (sidorder(SID))

    (filecon "\" any ())

    (filecon "" any ())

  When cil_post_fc_fill_data() processes "\", it goes beyond the NUL

  terminator of the string. Fix this by returning when '\0' is read

  after a backslash.

To be consistent with the function compute_diffdata() in

refpolicy/support/fc_sort.py, also increment str_len in this case.

Fixes: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=28484

Reported-by: Nicolas Iooss <nicolas.iooss@m4x.org>

Signed-off-by: James Carter <jwcart2@gmail.com>

---

 libsepol/cil/src/cil_post.c | 7 +++++++

 1 file changed, 7 insertions(+)

diff --git a/libsepol/cil/src/cil_post.c b/libsepol/cil/src/cil_post.c

index d2ecbd430aa3..fd4758dc580e 100644

--- a/libsepol/cil/src/cil_post.c

+++ b/libsepol/cil/src/cil_post.c

@@ -186,6 +186,13 @@ static void cil_post_fc_fill_data(struct fc_data *fc, const char *path)

 			break;

 		case '\\':

 			c++;

+			if (path[c] == '\0') {

+				if (!fc->meta) {

+					fc->stem_len++;

+				}

+				fc->str_len++;

+				return;

+			}

 			/* FALLTHRU */

 		default:

 			if (!fc->meta) {

-- 

2.32.0