[PATCH AUTOSEL 4.14 17/17] udf_get_extendedattr() had no boundary checks.

[Sasha Levin]

From: Stian Skjelstad <stian.skjelstad@xxxxxxxxx>

[ Upstream commit 58bc6d1be2f3b0ceecb6027dfa17513ec6aa2abb ]

When parsing the ExtendedAttr data, malicous or corrupt attribute length
could cause kernel hangs and buffer overruns in some special cases.

Link: https://lore.kernel.org/r/20210822093332.25234-1-stian.skjelstad@xxxxxxxxx
Signed-off-by: Stian Skjelstad <stian.skjelstad@xxxxxxxxx>
Signed-off-by: Jan Kara <jack@xxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 fs/udf/misc.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/fs/udf/misc.c b/fs/udf/misc.c
index 3949c4bec3a3..e5f4dcde309f 100644
--- a/fs/udf/misc.c
+++ b/fs/udf/misc.c
@@ -173,13 +173,22 @@ struct genericFormat *udf_get_extendedattr(struct inode *inode, uint32_t type,
 		else
 			offset = le32_to_cpu(eahd->appAttrLocation);
 
-		while (offset < iinfo->i_lenEAttr) {
+		while (offset + sizeof(*gaf) < iinfo->i_lenEAttr) {
+			uint32_t attrLength;
+
 			gaf = (struct genericFormat *)&ea[offset];
+			attrLength = le32_to_cpu(gaf->attrLength);
+
+			/* Detect undersized elements and buffer overflows */
+			if ((attrLength < sizeof(*gaf)) ||
+			    (attrLength > (iinfo->i_lenEAttr - offset)))
+				break;
+
 			if (le32_to_cpu(gaf->attrType) == type &&
 					gaf->attrSubtype == subtype)
 				return gaf;
 			else
-				offset += le32_to_cpu(gaf->attrLength);
+				offset += attrLength;
 		}
 	}
 
-- 
2.30.2