+ ocfs2-fix-readdir-position-truncation-on-32-bit-kernels.patch added to mm-nonmm-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: ocfs2: fix readdir position truncation on 32-bit kernels
has been added to the -mm mm-nonmm-unstable branch.  Its filename is
     ocfs2-fix-readdir-position-truncation-on-32-bit-kernels.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/ocfs2-fix-readdir-position-truncation-on-32-bit-kernels.patch

This patch will later appear in the mm-nonmm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Zhan Xusheng <zhanxusheng1024@gmail.com>
Subject: ocfs2: fix readdir position truncation on 32-bit kernels
Date: Thu, 6 Aug 2026 10:20:44 +0800

In ocfs2_dir_foreach_blk_el(), the directory cookie position is
rebuilt with

	ctx->pos = (ctx->pos & ~(sb->s_blocksize - 1)) | offset;

`ctx->pos` is loff_t (signed 64-bit), while `sb->s_blocksize` is
unsigned long.  On 32-bit kernels unsigned long is 32-bit, so the mask

	~(sb->s_blocksize - 1)

is computed as a 32-bit unsigned value (e.g. 0xfffff000 for a 4 KiB
block size).  In the AND expression with the 64-bit `ctx->pos`, that
unsigned operand is zero-extended to 64 bits per the usual arithmetic
conversions, yielding 0x00000000fffff000.  The high 32 bits of
`ctx->pos` are silently cleared, even though directory size is
allowed to exceed 4 GiB.

When readdir() crosses the 4 GiB boundary on a 32-bit kernel the
position is reset back into the first 4 GiB block, making the
re-validation path re-enumerate already-returned dirents indefinitely.

This is ocfs2_dir_foreach_blk_el(), the extent-list readdir path taken
for all non-inline directories, so a directory large enough to cross
4 GiB reaches it.

This is the same class of bug that commit 3dce5bb82c97 ("exfat: Fix
bitwise operation having different size") fixed in exfat, and the
fix mirrors the equivalent ext4 fix in this series.  Cast the operand
to loff_t so the mask is 64-bit before the AND:

	ctx->pos = (ctx->pos & ~((loff_t)sb->s_blocksize - 1)) | offset;

64-bit kernels are unaffected.

Link: https://lore.kernel.org/20260806022044.167962-3-zhanxusheng@xiaomi.com
Fixes: ccd979bdbce9 ("[PATCH] OCFS2: The Second Oracle Cluster Filesystem")
Signed-off-by: Zhan Xusheng <zhanxusheng@xiaomi.com>
Cc: Mark Fasheh <mark@fasheh.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Junxiao Bi <junxiao.bi@oracle.com>
Cc: Joseph Qi <jiangqi903@gmail.com>
Cc: Changwei Ge <gechangwei@live.cn>
Cc: Jun Piao <piaojun@huawei.com>
Cc: Heming Zhao <heming.zhao@suse.com>
Cc: Andreas Dilger <adilger.kernel@dilger.ca>
Cc: Jan Kara <jack@suse.cz>
Cc: Ojaswin Mujoo <ojaswin@linux.ibm.com>
Cc: "Ritesh Harjani (IBM)" <ritesh.list@gmail.com>
Cc: Ted Ts'o <tytso@mit.edu>
Cc: "zhangyi (F)" <yi.zhang@huawei.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 fs/ocfs2/dir.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/fs/ocfs2/dir.c~ocfs2-fix-readdir-position-truncation-on-32-bit-kernels
+++ a/fs/ocfs2/dir.c
@@ -1959,7 +1959,7 @@ static int ocfs2_dir_foreach_blk_el(stru
 				i += le16_to_cpu(de->rec_len);
 			}
 			offset = i;
-			ctx->pos = (ctx->pos & ~(sb->s_blocksize - 1))
+			ctx->pos = (ctx->pos & ~((loff_t)sb->s_blocksize - 1))
 				| offset;
 			*f_version = inode_query_iversion(inode);
 		}
_

Patches currently in -mm which might be from zhanxusheng1024@gmail.com are

ocfs2-fix-readdir-position-truncation-on-32-bit-kernels.patch