linux-kernel - [PATCH] ext4: move ext4_percpu_param_init() before ext4_mb

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-Id: <20251209133116.731350-1-libaokun@huaweicloud.com>
Date: Tue,  9 Dec 2025 21:31:16 +0800
From: libaokun@...weicloud.com
To: linux-ext4@...r.kernel.org
Cc: tytso@....edu,
	adilger.kernel@...ger.ca,
	jack@...e.cz,
	linux-kernel@...r.kernel.org,
	yi.zhang@...wei.com,
	yangerkun@...wei.com,
	libaokun1@...wei.com,
	libaokun@...weicloud.com
Subject: [PATCH] ext4: move ext4_percpu_param_init() before ext4_mb_init()

From: Baokun Li <libaokun1@...wei.com>

When running `kvm-xfstests -c ext4/1k -C 1 generic/383` with the
`DOUBLE_CHECK` macro defined, the following panic is triggered:

==================================================================
EXT4-fs error (device vdc): ext4_validate_block_bitmap:423:
                        comm mount: bg 0: bad block bitmap checksum
BUG: unable to handle page fault for address: ff110000fa2cc000
PGD 3e01067 P4D 3e02067 PUD 0
Oops: Oops: 0000 [#1] SMP NOPTI
CPU: 0 UID: 0 PID: 2386 Comm: mount Tainted: G W
                        6.18.0-gba65a4e7120a-dirty #1152 PREEMPT(none)
RIP: 0010:percpu_counter_add_batch+0x13/0xa0
Call Trace:
 <TASK>
 ext4_mark_group_bitmap_corrupted+0xcb/0xe0
 ext4_validate_block_bitmap+0x2a1/0x2f0
 ext4_read_block_bitmap+0x33/0x50
 mb_group_bb_bitmap_alloc+0x33/0x80
 ext4_mb_add_groupinfo+0x190/0x250
 ext4_mb_init_backend+0x87/0x290
 ext4_mb_init+0x456/0x640
 __ext4_fill_super+0x1072/0x1680
 ext4_fill_super+0xd3/0x280
 get_tree_bdev_flags+0x132/0x1d0
 vfs_get_tree+0x29/0xd0
 vfs_cmd_create+0x59/0xe0
 __do_sys_fsconfig+0x4f6/0x6b0
 do_syscall_64+0x50/0x1f0
 entry_SYSCALL_64_after_hwframe+0x76/0x7e
==================================================================

This issue can be reproduced using the following commands:
        mkfs.ext4 -F -q -b 1024 /dev/sda 5G
        tune2fs -O quota,project /dev/sda
        mount /dev/sda /tmp/test

With DOUBLE_CHECK defined, mb_group_bb_bitmap_alloc() reads
and validates the block bitmap. When the validation fails,
ext4_mark_group_bitmap_corrupted() attempts to update
sbi->s_freeclusters_counter. However, this percpu_counter has not been
initialized yet at this point, which leads to the panic described above.

Fix this by moving the execution of ext4_percpu_param_init() to occur
before ext4_mb_init(), ensuring the per-CPU counters are initialized
before they are used.

Signed-off-by: Baokun Li <libaokun1@...wei.com>
---
 fs/ext4/super.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 87205660c5d0..5c2e931d8a53 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -5599,35 +5599,35 @@ static int __ext4_fill_super(struct fs_context *fc, struct super_block *sb)
 	 */
 	if (!(ctx->spec & EXT4_SPEC_mb_optimize_scan)) {
 		if (sbi->s_groups_count >= MB_DEFAULT_LINEAR_SCAN_THRESHOLD)
 			set_opt2(sb, MB_OPTIMIZE_SCAN);
 		else
 			clear_opt2(sb, MB_OPTIMIZE_SCAN);
 	}
 
+	err = ext4_percpu_param_init(sbi);
+	if (err)
+		goto failed_mount5;
+
 	err = ext4_mb_init(sb);
 	if (err) {
 		ext4_msg(sb, KERN_ERR, "failed to initialize mballoc (%d)",
 			 err);
 		goto failed_mount5;
 	}
 
 	/*
 	 * We can only set up the journal commit callback once
 	 * mballoc is initialized
 	 */
 	if (sbi->s_journal)
 		sbi->s_journal->j_commit_callback =
 			ext4_journal_commit_callback;
 
-	err = ext4_percpu_param_init(sbi);
-	if (err)
-		goto failed_mount6;
-
 	if (ext4_has_feature_flex_bg(sb))
 		if (!ext4_fill_flex_info(sb)) {
 			ext4_msg(sb, KERN_ERR,
 			       "unable to initialize "
 			       "flex_bg meta info!");
 			err = -ENOMEM;
 			goto failed_mount6;
 		}
@@ -5699,18 +5699,18 @@ static int __ext4_fill_super(struct fs_context *fc, struct super_block *sb)
 	ext4_quotas_off(sb, EXT4_MAXQUOTAS);
 failed_mount8: __maybe_unused
 	ext4_release_orphan_info(sb);
 failed_mount7:
 	ext4_unregister_li_request(sb);
 failed_mount6:
 	ext4_mb_release(sb);
 	ext4_flex_groups_free(sbi);
-	ext4_percpu_param_destroy(sbi);
 failed_mount5:
+	ext4_percpu_param_destroy(sbi);
 	ext4_ext_release(sb);
 	ext4_release_system_zone(sb);
 failed_mount4a:
 	dput(sb->s_root);
 	sb->s_root = NULL;
 failed_mount4:
 	ext4_msg(sb, KERN_ERR, "mount failed");
 	if (EXT4_SB(sb)->rsv_conversion_wq)
-- 
2.39.2