Re: [PATCH 5.15.y] ocfs2: fix shift-out-of-bounds UBSAN bug in ocfs2_verify_volume

[Greg KH]

On Tue, Mar 24, 2026 at 07:04:58AM +0000, 10163...@qq.com wrote:
> This patch is a backport to stable 5.15.y of upstream commit
> 7f86b2942791012ac7b4c481d1f84a58fd2fbcfc
> ("ocfs2: fix shift-out-of-bounds UBSAN bug in ocfs2_verify_volume()").

This was attached, and could not be applied directly. Please submit the
patch inline.

thanks,

greg k-h

[10163...@qq.com]

This patch is a backport to stable 5.15.y of upstream commit

7f86b2942791012ac7b4c481d1f84a58fd2fbcfc

("ocfs2: fix shift-out-of-bounds UBSAN bug in ocfs2_verify_volume()").

This patch addresses a shift-out-of-bounds error in the

ocfs2_verify_volume() function. The bug can be triggered by an invalid

s_clustersize_bits value, which causes the expression

  1 << le32_to_cpu(di->id2.i_super.s_clustersize_bits)

to exceed the valid shift range of a 32-bit integer, leading to an

out-of-bounds shift reported by UBSAN.

Instead of performing the invalid shift while printing the error message,

log the raw s_clustersize_bits value directly.

This backport was also tested by syzbot on Linux 5.15.201

(commit 3330a8d33e086f76608bb4e80a3dc569d04a8814 in the stable 5.15.y

tree), and the reproducer did not trigger any issue.

[ Upstream commit 7f86b2942791012ac7b4c481d1f84a58fd2fbcfc ]

Link: https://lkml.kernel.org/r/ZsPvwQAXd5R/jNY+@hostname

Reported-by: syzbot <syzbot+f3fff7...@syzkaller.appspotmail.com>

Closes: https://syzkaller.appspot.com/bug?extid=f3fff775402751ebb471

Tested-by: syzbot <syzbot+f3fff7...@syzkaller.appspotmail.com>

Reviewed-by: Joseph Qi <jose...@linux.alibaba.com>

Link: https://syzkaller.appspot.com/bug?extid=c6104ecfe56e0fd6b616

Tested-by: syzbot <syzbot+c6104e...@syzkaller.appspotmail.com>

Signed-off-by: Qasim Ijaz <qasd...@gmail.com>

Signed-off-by: Changjian Liu <dri...@qq.com>

[10163...@qq.com]

---

 fs/ocfs2/super.c | 4 ++--

 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/ocfs2/super.c b/fs/ocfs2/super.c

index bb174009206e..ae2ba616756d 100644

--- a/fs/ocfs2/super.c

+++ b/fs/ocfs2/super.c

@@ -2369,8 +2369,8 @@ static int ocfs2_verify_volume(struct ocfs2_dinode *di,

                       (unsigned long long)bh->b_blocknr);

            } else if (le32_to_cpu(di->id2.i_super.s_clustersize_bits) < 12 ||

                      le32_to_cpu(di->id2.i_super.s_clustersize_bits) > 20) {

-                 mlog(ML_ERROR, "bad cluster size found: %u\n",

-                      1 << le32_to_cpu(di->id2.i_super.s_clustersize_bits));

+                 mlog(ML_ERROR, "bad cluster size bit found: %u\n",

+                      le32_to_cpu(di->id2.i_super.s_clustersize_bits));

            } else if (!le64_to_cpu(di->id2.i_super.s_root_blkno)) {

                  mlog(ML_ERROR, "bad root_blkno: 0\n");

            } else if (!le64_to_cpu(di->id2.i_super.s_system_dir_blkno)) {

--

2.43.0

[10163...@qq.com]