From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0A4E8395250 for ; Thu, 2 Apr 2026 17:40:40 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775151640; cv=none; b=Pc2ta1GMi54HhG0zvpwRwHkqJD8PUP7RHV1NRLYnzWzdgYPwH/zsL3t+CCgo6rOZeSwREpr7OSri2tr3MlVtKVMbDA9yflf+uobqdpKatmAgn6f4i586bCMABY20qF3xuP+kbUFJcWwdJ8MdPggt4CEM+gOIkzx9gNdWkCvx4lk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775151640; c=relaxed/simple; bh=E6Ku1GQ69800RD7GhETWmaQR1qPmmViDLnmlc9d25j4=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=tPTwyXq/cNoW6dOZJYx+3TJhDE6+881ddqMaaIBynHYfce0Uamb6AmIAMegugruQCYKRHp7Ovf13scLwzW4bOM+dYJR8ye88vUj5QL3wg5ZhxKhMgjb8TrDder/LM9KhmxhN5zGIWtQoGr82XrtISnN9bhUhdL2vw8bpH9XWaXM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=YBdv61by; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="YBdv61by" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 400FCC116C6; Thu, 2 Apr 2026 17:40:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1775151639; bh=E6Ku1GQ69800RD7GhETWmaQR1qPmmViDLnmlc9d25j4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=YBdv61byGRDspSgs8H1a1gGPUZ4KoY/b3JRjJ++uJUb15SaasZsKSUyASGBig5DYE SQyk4x31lmLRYtb0KT2omKR+BjkjwLekkkwzxmqQxi++hncdiKgedw/IzzJ4/dNI7j VhZCxL4wwvOrZ8aGogpY7ANagxmoil24Rowl7DDPXG0+ioqhs+GKwr71gOzz1X0mBD Lx/ajX2JlS52iz2u12ZIWi4+QJjwFg0G5C1XyBczYdtea59c7fyv371OyJBds1TONI MkNxNoxnvvPTeXheERFG2rviou5BF1Fw04Fe1kfpTyDhkKtpYceDXa9l+QHh3drkiU Qz2ndOElZnSlA== From: Sasha Levin To: stable@vger.kernel.org Cc: Zqiang , Baokun Li , Theodore Ts'o , stable@kernel.org, Sasha Levin Subject: [PATCH 5.10.y] ext4: fix the might_sleep() warnings in kvfree() Date: Thu, 2 Apr 2026 13:40:37 -0400 Message-ID: <20260402174037.1571365-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <2026033018-tiring-matching-ee63@gregkh> References: <2026033018-tiring-matching-ee63@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Zqiang [ Upstream commit 496bb99b7e66f48b178126626f47e9ba79e2d0fa ] Use the kvfree() in the RCU read critical section can trigger the following warnings: EXT4-fs (vdb): unmounting filesystem cd983e5b-3c83-4f5a-a136-17b00eb9d018. WARNING: suspicious RCU usage ./include/linux/rcupdate.h:409 Illegal context switch in RCU read-side critical section! other info that might help us debug this: rcu_scheduler_active = 2, debug_locks = 1 Call Trace: dump_stack_lvl+0xbb/0xd0 dump_stack+0x14/0x20 lockdep_rcu_suspicious+0x15a/0x1b0 __might_resched+0x375/0x4d0 ? put_object.part.0+0x2c/0x50 __might_sleep+0x108/0x160 vfree+0x58/0x910 ? ext4_group_desc_free+0x27/0x270 kvfree+0x23/0x40 ext4_group_desc_free+0x111/0x270 ext4_put_super+0x3c8/0xd40 generic_shutdown_super+0x14c/0x4a0 ? __pfx_shrinker_free+0x10/0x10 kill_block_super+0x40/0x90 ext4_kill_sb+0x6d/0xb0 deactivate_locked_super+0xb4/0x180 deactivate_super+0x7e/0xa0 cleanup_mnt+0x296/0x3e0 __cleanup_mnt+0x16/0x20 task_work_run+0x157/0x250 ? __pfx_task_work_run+0x10/0x10 ? exit_to_user_mode_loop+0x6a/0x550 exit_to_user_mode_loop+0x102/0x550 do_syscall_64+0x44a/0x500 entry_SYSCALL_64_after_hwframe+0x77/0x7f BUG: sleeping function called from invalid context at mm/vmalloc.c:3441 in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 556, name: umount preempt_count: 1, expected: 0 CPU: 3 UID: 0 PID: 556 Comm: umount Call Trace: dump_stack_lvl+0xbb/0xd0 dump_stack+0x14/0x20 __might_resched+0x275/0x4d0 ? put_object.part.0+0x2c/0x50 __might_sleep+0x108/0x160 vfree+0x58/0x910 ? ext4_group_desc_free+0x27/0x270 kvfree+0x23/0x40 ext4_group_desc_free+0x111/0x270 ext4_put_super+0x3c8/0xd40 generic_shutdown_super+0x14c/0x4a0 ? __pfx_shrinker_free+0x10/0x10 kill_block_super+0x40/0x90 ext4_kill_sb+0x6d/0xb0 deactivate_locked_super+0xb4/0x180 deactivate_super+0x7e/0xa0 cleanup_mnt+0x296/0x3e0 __cleanup_mnt+0x16/0x20 task_work_run+0x157/0x250 ? __pfx_task_work_run+0x10/0x10 ? exit_to_user_mode_loop+0x6a/0x550 exit_to_user_mode_loop+0x102/0x550 do_syscall_64+0x44a/0x500 entry_SYSCALL_64_after_hwframe+0x77/0x7f The above scenarios occur in initialization failures and teardown paths, there are no parallel operations on the resources released by kvfree(), this commit therefore remove rcu_read_lock/unlock() and use rcu_access_pointer() instead of rcu_dereference() operations. Fixes: 7c990728b99e ("ext4: fix potential race between s_flex_groups online resizing and access") Fixes: df3da4ea5a0f ("ext4: fix potential race between s_group_info online resizing and access") Signed-off-by: Zqiang Reviewed-by: Baokun Li Link: https://patch.msgid.link/20260319094545.19291-1-qiang.zhang@linux.dev Signed-off-by: Theodore Ts'o Cc: stable@kernel.org [ adapted inline rcu_read_lock/rcu_dereference/rcu_read_unlock removal ] Signed-off-by: Sasha Levin --- fs/ext4/mballoc.c | 10 +++------- fs/ext4/super.c | 6 ++---- 2 files changed, 5 insertions(+), 11 deletions(-) diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c index d1a616bbb5bdb..e2d79b7642623 100644 --- a/fs/ext4/mballoc.c +++ b/fs/ext4/mballoc.c @@ -2890,9 +2890,7 @@ static int ext4_mb_init_backend(struct super_block *sb) rcu_read_unlock(); iput(sbi->s_buddy_cache); err_freesgi: - rcu_read_lock(); - kvfree(rcu_dereference(sbi->s_group_info)); - rcu_read_unlock(); + kvfree(rcu_access_pointer(sbi->s_group_info)); return -ENOMEM; } @@ -3084,7 +3082,8 @@ int ext4_mb_release(struct super_block *sb) struct kmem_cache *cachep = get_groupinfo_cache(sb->s_blocksize_bits); int count; - if (sbi->s_group_info) { + group_info = rcu_access_pointer(sbi->s_group_info); + if (group_info) { for (i = 0; i < ngroups; i++) { cond_resched(); grinfo = ext4_get_group_info(sb, i); @@ -3102,12 +3101,9 @@ int ext4_mb_release(struct super_block *sb) num_meta_group_infos = (ngroups + EXT4_DESC_PER_BLOCK(sb) - 1) >> EXT4_DESC_PER_BLOCK_BITS(sb); - rcu_read_lock(); - group_info = rcu_dereference(sbi->s_group_info); for (i = 0; i < num_meta_group_infos; i++) kfree(group_info[i]); kvfree(group_info); - rcu_read_unlock(); } kfree(sbi->s_mb_offsets); kfree(sbi->s_mb_maxs); diff --git a/fs/ext4/super.c b/fs/ext4/super.c index 41e49fee35e5a..c86663e5e1d9a 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -1207,18 +1207,16 @@ static void ext4_put_super(struct super_block *sb) if (!sb_rdonly(sb)) ext4_commit_super(sb, 1); - rcu_read_lock(); - group_desc = rcu_dereference(sbi->s_group_desc); + group_desc = rcu_access_pointer(sbi->s_group_desc); for (i = 0; i < sbi->s_gdb_count; i++) brelse(group_desc[i]); kvfree(group_desc); - flex_groups = rcu_dereference(sbi->s_flex_groups); + flex_groups = rcu_access_pointer(sbi->s_flex_groups); if (flex_groups) { for (i = 0; i < sbi->s_flex_groups_allocated; i++) kvfree(flex_groups[i]); kvfree(flex_groups); } - rcu_read_unlock(); percpu_counter_destroy(&sbi->s_freeclusters_counter); percpu_counter_destroy(&sbi->s_freeinodes_counter); percpu_counter_destroy(&sbi->s_dirs_counter); -- 2.53.0