[PATCH AUTOSEL 4.14 078/127] ubifs: Fix out-of-bounds memory access caused by abnormal value of node_len

Sasha Levin
2020-09-18T02:32:58Z

From: Liu Song <liu.song11@zte.com.cn>

[ 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>
---
fs/ubifs/io.c | 16 ++++++++++++++--
1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/fs/ubifs/io.c b/fs/ubifs/io.c
index 3be28900bf375..135e95950f513 100644
--- a/fs/ubifs/io.c
+++ b/fs/ubifs/io.c
@@ -237,7 +237,7 @@ 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;

@@ -290,10 +290,22 @@ 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;
--
2.25.1