linux-kernel - [PATCH] hfsplus: add check for cat key length

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Message-ID: <tencent_E298974436464AA47527762F67923C3D3609@qq.com>
Date: Wed,  6 Nov 2024 17:58:07 +0800
From: Edward Adam Davis <eadavis@...com>
To: syzbot+968ecf5dc01b3e0148ec@...kaller.appspotmail.com
Cc: linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	syzkaller-bugs@...glegroups.com
Subject: [PATCH] hfsplus: add check for cat key length

Syzbot reported a uninit-value in hfsplus_cat_bin_cmp_key.
The result of reading from the raw data of the node in hfs_bnode_read_u16()
is 0, and the final calculated catalog key length is 2, which will eventually
lead to too little key data read from the node to initialize the parent member
of struct hfsplus_cat_key.

The solution is to increase the key length judgment, and terminate the
subsequent operations if it is too small.

#syz test

Reported-by: syzbot+968ecf5dc01b3e0148ec@...kaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=968ecf5dc01b3e0148ec
Signed-off-by: Edward Adam Davis <eadavis@...com>
---
 fs/hfsplus/brec.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/fs/hfsplus/brec.c b/fs/hfsplus/brec.c
index 1918544a7871..da38638ad808 100644
--- a/fs/hfsplus/brec.c
+++ b/fs/hfsplus/brec.c
@@ -51,6 +51,13 @@ u16 hfs_brec_keylen(struct hfs_bnode *node, u16 rec)
 		}
 
 		retval = hfs_bnode_read_u16(node, recoff) + 2;
+		if (node->tree->cnid == HFSPLUS_CAT_CNID &&
+		    retval < offsetof(struct hfsplus_cat_key, parent) +
+			     sizeof(hfsplus_cnid)) {
+			pr_err("keylen %d too small\n",
+				retval);
+			return 0;
+		}
 		if (retval > node->tree->max_key_len + 2) {
 			pr_err("keylen %d too large\n",
 				retval);
-- 
2.43.0