linux-kernel - [PATCH] ubifs: Fail commit if TNC is obviously inconsistent

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Message-Id: <20170607213335.23059-1-richard@nod.at>
Date:   Wed,  7 Jun 2017 23:33:35 +0200
From:   Richard Weinberger <richard@....at>
To:     linux-mtd@...ts.infradead.org
Cc:     linux-kernel@...r.kernel.org, adrian.hunter@...el.com,
        dedekind1@...il.com, Richard Weinberger <richard@....at>
Subject: [PATCH] ubifs: Fail commit if TNC is obviously inconsistent

A reference to LEB 0 or with length 0 in the TNC
is never correct and could be caused by a memory corruption.
Don't write such a bad index node to the MTD.
Instead fail the commit which will turn UBIFS into read-only mode.

This is less painful than having the bad reference on the MTD
from where UBFIS has no chance to recover.

Signed-off-by: Richard Weinberger <richard@....at>
---
 fs/ubifs/tnc_commit.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/fs/ubifs/tnc_commit.c b/fs/ubifs/tnc_commit.c
index 51157da3f76e..aa31f60220ef 100644
--- a/fs/ubifs/tnc_commit.c
+++ b/fs/ubifs/tnc_commit.c
@@ -57,6 +57,8 @@ static int make_idx_node(struct ubifs_info *c, struct ubifs_idx_node *idx,
 			ubifs_dump_znode(c, znode);
 			if (zbr->znode)
 				ubifs_dump_znode(c, zbr->znode);
+
+			return -EINVAL;
 		}
 	}
 	ubifs_prepare_node(c, idx, len, 0);
@@ -859,6 +861,8 @@ static int write_index(struct ubifs_info *c)
 				ubifs_dump_znode(c, znode);
 				if (zbr->znode)
 					ubifs_dump_znode(c, zbr->znode);
+
+				return -EINVAL;
 			}
 		}
 		len = ubifs_idx_node_sz(c, znode->child_cnt);
-- 
2.12.3