linux-kernel - [PATCH] erofs: Prohibit access to excessive algorithmformat

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Message-ID: <tencent_FC33559E331B7F4BA91BB62522BA1CBB8C08@qq.com>
Date: Sat, 23 Aug 2025 09:53:37 +0800
From: Edward Adam Davis <eadavis@...com>
To: syzbot+5a398eb460ddaa6f242f@...kaller.appspotmail.com
Cc: chao@...nel.org,
	dhavale@...gle.com,
	jefflexu@...ux.alibaba.com,
	lihongbo22@...wei.com,
	linux-erofs@...ts.ozlabs.org,
	linux-kernel@...r.kernel.org,
	syzkaller-bugs@...glegroups.com,
	xiang@...nel.org,
	zbestahu@...il.com
Subject: [PATCH] erofs: Prohibit access to excessive algorithmformat

syz reported a global-out-of-bounds Read in z_erofs_decompress_queue.

OOB occurs in z_erofs_decompress_queue() because algorithmformat is too
large.

Added relevant checks when registering pcluster.

Reported-by: syzbot+5a398eb460ddaa6f242f@...kaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=5a398eb460ddaa6f242f
Tested-by: syzbot+5a398eb460ddaa6f242f@...kaller.appspotmail.com
Signed-off-by: Edward Adam Davis <eadavis@...com>
---
 fs/erofs/zdata.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c
index 2d73297003d2..085fa0685a57 100644
--- a/fs/erofs/zdata.c
+++ b/fs/erofs/zdata.c
@@ -762,6 +762,10 @@ static int z_erofs_register_pcluster(struct z_erofs_frontend *fe)
 	pcl->from_meta = map->m_flags & EROFS_MAP_META;
 	fe->mode = Z_EROFS_PCLUSTER_FOLLOWED;
 
+	if (pcl->algorithmformat >= Z_EROFS_COMPRESSION_MAX) {
+		err = -EINVAL;
+		goto out;
+	}
 	/*
 	 * lock all primary followed works before visible to others
 	 * and mutex_trylock *never* fails for a new pcluster.
@@ -796,6 +800,7 @@ static int z_erofs_register_pcluster(struct z_erofs_frontend *fe)
 
 err_out:
 	mutex_unlock(&pcl->lock);
+out:
 	z_erofs_free_pcluster(pcl);
 	return err;
 }
-- 
2.43.0