ubifs: Fix out-of-bounds memory access caused by abnormal value of node_len

BugLink: https://bugs.launchpad.net/bugs/1900624
[ Upstream commit acc5af3efa303d5f36cc8c0f61716161f6ca1384 ]

In “ubifs_check_node”, when the value of "node_len" is abnormal,
the code will goto label of "out_len" for execution. Then, in the
following "ubifs_dump_node", if inode type is "UBIFS_DATA_NODE",
in "print_hex_dump", an out-of-bounds access may occur due to the
wrong "ch->len".

Therefore, when the value of "node_len" is abnormal, data length
should to be adjusted to a reasonable safe range. At this time,
structured data is not credible, so dump the corrupted data directly
for analysis.

Signed-off-by: Liu Song <liu.song11@zte.com.cn>
Signed-off-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Ian May <ian.may@canonical.com>

diff --git a/fs/ubifs/io.c b/fs/ubifs/io.c
index 8ceb51478800b59e78bae92b309815cbc9f380fc..7e4bfaf2871fa0907f5cacf7b5f006a79106878f 100644 (file)
--- a/fs/ubifs/io.c
+++ b/fs/ubifs/io.c
@@ -225,7 +225,7 @@ int ubifs_is_mapped(const struct ubifs_info *c, int lnum)
 int ubifs_check_node(const struct ubifs_info *c, const void *buf, int lnum,
                     int offs, int quiet, int must_chk_crc)
 {
-       int err = -EINVAL, type, node_len;
+       int err = -EINVAL, type, node_len, dump_node = 1;
        uint32_t crc, node_crc, magic;
        const struct ubifs_ch *ch = buf;
 
@@ -278,10 +278,22 @@ int ubifs_check_node(const struct ubifs_info *c, const void *buf, int lnum,
 out_len:
        if (!quiet)
                ubifs_err(c, "bad node length %d", node_len);
+       if (type == UBIFS_DATA_NODE && node_len > UBIFS_DATA_NODE_SZ)
+               dump_node = 0;
 out:
        if (!quiet) {
                ubifs_err(c, "bad node at LEB %d:%d", lnum, offs);
-               ubifs_dump_node(c, buf);
+               if (dump_node) {
+                       ubifs_dump_node(c, buf);
+               } else {
+                       int safe_len = min3(node_len, c->leb_size - offs,
+                               (int)UBIFS_MAX_DATA_NODE_SZ);
+                       pr_err("\tprevent out-of-bounds memory access\n");
+                       pr_err("\ttruncated data node length      %d\n", safe_len);
+                       pr_err("\tcorrupted data node:\n");
+                       print_hex_dump(KERN_ERR, "\t", DUMP_PREFIX_OFFSET, 32, 1,
+                                       buf, safe_len, 0);
+               }
                dump_stack();
        }
        return err;