linux-kernel - [PATCH v2] jfs: fix array-index-out-of-bounds in diAlloc

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Date:   Wed,  4 Oct 2023 13:10:40 +0530
From:   Manas Ghandat <ghandatmanas@...il.com>
To:     dave.kleikamp@...cle.com, shaggy@...nel.org
Cc:     Manas Ghandat <ghandatmanas@...il.com>,
        Linux-kernel-mentees@...ts.linuxfoundation.org,
        jfs-discussion@...ts.sourceforge.net, linux-kernel@...r.kernel.org,
        syzbot+79d792676d8ac050949f@...kaller.appspotmail.com
Subject: [PATCH v2] jfs: fix array-index-out-of-bounds in diAlloc

Currently there is not check against the agno of the iag while
allocating new inodes to avoid fragmentation problem. Added the check
which is required.

Reported-by: syzbot+79d792676d8ac050949f@...kaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=79d792676d8ac050949f
Signed-off-by: Manas Ghandat <ghandatmanas@...il.com>
---
V1 -> V2 : Added check for higher bound of agno
 fs/jfs/jfs_imap.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/fs/jfs/jfs_imap.c b/fs/jfs/jfs_imap.c
index 799d3837e7c2..c0cf74e7392b 100644
--- a/fs/jfs/jfs_imap.c
+++ b/fs/jfs/jfs_imap.c
@@ -1319,7 +1319,7 @@ diInitInode(struct inode *ip, int iagno, int ino, int extno, struct iag * iagp)
 int diAlloc(struct inode *pip, bool dir, struct inode *ip)
 {
 	int rc, ino, iagno, addext, extno, bitno, sword;
-	int nwords, rem, i, agno;
+	int nwords, rem, i, agno, dn_numag;
 	u32 mask, inosmap, extsmap;
 	struct inode *ipimap;
 	struct metapage *mp;
@@ -1355,6 +1355,9 @@ int diAlloc(struct inode *pip, bool dir, struct inode *ip)
 
 	/* get the ag number of this iag */
 	agno = BLKTOAG(JFS_IP(pip)->agstart, JFS_SBI(pip->i_sb));
+	dn_numag = JFS_SBI(pip->i_sb)->bmap->db_numag;
+	if (agno < 0 || agno > dn_numag)
+		return -EIO;
 
 	if (atomic_read(&JFS_SBI(pip->i_sb)->bmap->db_active[agno])) {
 		/*
-- 
2.37.2