[PATCH v2] hfsplus: validate inline xattr record size against entrylength

[Hui Peng <benquike@gmail.com>]

In __hfsplus_getxattr(), record_length is read from the on-disk
hfsplus_attr_inline_data header and only checked against
HFSPLUS_MAX_INLINE_DATA_SIZE without verifying that fd.entrylength is
large enough to hold the inline header and record_length bytes of
raw_bytes. A corrupted attribute B-tree node where record_length exceeds
fd.entrylength causes hfs_bnode_read() to read past the end of the B-tree
record (and potentially across the bnode boundary).

Validate fd.entrylength before reading xattr_record_type, length, and
raw_bytes.

Tested in QEMU against Linux 7.3.0-rc3 by mounting a crafted HFS+ image
containing an inline xattr record where record_length (100) exceeded
fd.entrylength (4): on the unfixed kernel, __hfsplus_getxattr() read past
the end of the B-tree record; whereas with this fix applied,
__hfsplus_getxattr() rejects the malformed record with "invalid xattr
record size" (-EIO).

Fixes: 127e5f5ae51e ("hfsplus: rework functionality of getting, setting and deleting of extended attributes")
Cc: stable@vger.kernel.org
Assisted-by: LLM
Signed-off-by: Hui Peng <benquike@gmail.com>
---
Changes in v2:
- Drop the hidden_dir cleanup hunk (already covered by Deepanshu
  Kartikey's patch series) and focus solely on the __hfsplus_getxattr()
  entrylength validation, as requested by Viacheslav Dubeyko.

 fs/hfsplus/xattr.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/fs/hfsplus/xattr.c b/fs/hfsplus/xattr.c
index 21a1c196c71f..10aae766ea42 100644
--- a/fs/hfsplus/xattr.c
+++ b/fs/hfsplus/xattr.c
@@ -649,15 +649,28 @@ ssize_t __hfsplus_getxattr(struct inode *inode, const char *name,
 		goto out;
 	}
 
+	if (fd.entrylength < sizeof(xattr_record_type)) {
+		pr_err("invalid xattr record size\n");
+		res = -EIO;
+		goto out;
+	}
 	hfs_bnode_read(fd.bnode, &xattr_record_type,
 			fd.entryoffset, sizeof(xattr_record_type));
 	record_type = be32_to_cpu(xattr_record_type);
 	if (record_type == HFSPLUS_ATTR_INLINE_DATA) {
+		if (fd.entrylength < offsetof(struct hfsplus_attr_inline_data,
+					      raw_bytes)) {
+			pr_err("invalid xattr record size\n");
+			res = -EIO;
+			goto out;
+		}
 		record_length = hfs_bnode_read_u16(fd.bnode,
 				fd.entryoffset +
 				offsetof(struct hfsplus_attr_inline_data,
 				length));
-		if (record_length > HFSPLUS_MAX_INLINE_DATA_SIZE) {
+		if (record_length > HFSPLUS_MAX_INLINE_DATA_SIZE ||
+		    offsetof(struct hfsplus_attr_inline_data, raw_bytes) +
+		    record_length > fd.entrylength) {
 			pr_err("invalid xattr record size\n");
 			res = -EIO;
 			goto out;
-- 
2.55.0.1082.g2b9226bbc0-goog