Syzbot test for ocfs2: Add check for total number of chains in chain list

Posted by Prithvi Tambewagh 1 month, 2 weeks ago

#syz test git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 36c254515dc6592c44db77b84908358979dd6b50

Signed-off-by: Prithvi Tambewagh <activprithvi@gmail.com>
---
 fs/ocfs2/suballoc.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/fs/ocfs2/suballoc.c b/fs/ocfs2/suballoc.c
index f7b483f0de2a..7ea63e9cc4f8 100644
--- a/fs/ocfs2/suballoc.c
+++ b/fs/ocfs2/suballoc.c
@@ -671,6 +671,21 @@ static int ocfs2_block_group_alloc(struct ocfs2_super *osb,
 	BUG_ON(ocfs2_is_cluster_bitmap(alloc_inode));
 
 	cl = &fe->id2.i_chain;
+	unsigned int block_size = osb->sb->s_blocksize;
+	unsigned int max_cl_count =
+	(block_size - offsetof(struct ocfs2_chain_list, cl_recs)) /
+	sizeof(struct ocfs2_chain_rec);
+
+	if (!le16_to_cpu(cl->cl_count) ||
+	    le16_to_cpu(cl->cl_count) > max_cl_count) {
+		ocfs2_error(osb->sb,
+			    "Invalid chain list: cl_count %u "
+			    "exceeds max %u",
+			    le16_to_cpu(cl->cl_count), max_cl_count);
+		status = -EIO;
+		goto bail;
+	}
+
 	status = ocfs2_reserve_clusters_with_limit(osb,
 						   le16_to_cpu(cl->cl_cpg),
 						   max_block, flags, &ac);

base-commit: 36c254515dc6592c44db77b84908358979dd6b50
-- 
2.34.1

Re: [syzbot] [ocfs2?] KASAN: slab-use-after-free Read in ocfs2_reserve_suballoc_bits

Posted by syzbot 1 month, 2 weeks ago

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-by: syzbot+af14efe17dfa46173239@syzkaller.appspotmail.com
Tested-by: syzbot+af14efe17dfa46173239@syzkaller.appspotmail.com

Tested on:

commit:         36c25451 Merge tag 'powerpc-6.12-4' of git://git.kerne..
git tree:       git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
console output: https://syzkaller.appspot.com/x/log.txt?x=152cd984580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=cb22c32016cc7ad7
dashboard link: https://syzkaller.appspot.com/bug?extid=af14efe17dfa46173239
compiler:       Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
patch:          https://syzkaller.appspot.com/x/patch.diff?x=169e1b1a580000

Note: testing is done by a robot and is best-effort only.