linux-kernel - Re: [syzbot] [v9fs?] UBSAN: shift-out-of-bounds in v9fs_get

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Message-ID: <20250822134548.415-1-yuichtsu@amazon.com>
Date: Fri, 22 Aug 2025 22:45:48 +0900
From: Yuichiro Tsuji <yuichtsu@...zon.com>
To: <syzbot+30c83da54e948f6e9436@...kaller.appspotmail.com>
CC: <linux-kernel@...r.kernel.org>, <syzkaller-bugs@...glegroups.com>
Subject: Re: [syzbot] [v9fs?] UBSAN: shift-out-of-bounds in v9fs_get_tree

#syz test

diff --git a/fs/9p/vfs_super.c b/fs/9p/vfs_super.c
index 795c6388744c..3947ef762aaa 100644
--- a/fs/9p/vfs_super.c
+++ b/fs/9p/vfs_super.c
@@ -59,7 +59,7 @@ v9fs_fill_super(struct super_block *sb, struct v9fs_session_info *v9ses, int flags)
        sb->s_maxbytes = MAX_LFS_FILESIZE;
        sb->s_blocksize_bits = fls(v9ses->maxdata - 1);
-       sb->s_blocksize = 1 << sb->s_blocksize_bits;
+       sb->s_blocksize = BIT(sb->s_blocksize_bits);
        sb->s_magic = V9FS_MAGIC;
        if (v9fs_proto_dotl(v9ses)) {
                sb->s_op = &v9fs_super_ops_dotl;