From 496bb99b7e66f48b178126626f47e9ba79e2d0fa Mon Sep 17 00:00:00 2001 From: Zqiang Date: Thu, 19 Mar 2026 17:45:45 +0800 Subject: [PATCH] ext4: fix the might_sleep() warnings in kvfree() 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 --- fs/ext4/mballoc.c | 10 +++------- fs/ext4/super.c | 8 ++------ 2 files changed, 5 insertions(+), 13 deletions(-) diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c index 93d37f6cf9c3..bb6faebf9b6d 100644 --- a/fs/ext4/mballoc.c +++ b/fs/ext4/mballoc.c @@ -3584,9 +3584,7 @@ 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; } @@ -3901,7 +3899,8 @@ void ext4_mb_release(struct super_block *sb) WARN_ON_ONCE(!list_empty(&sbi->s_discard_list)); } - 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); @@ -3919,12 +3918,9 @@ void 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(); } ext4_mb_avg_fragment_size_destroy(sbi); ext4_mb_largest_free_orders_destroy(sbi); diff --git a/fs/ext4/super.c b/fs/ext4/super.c index 152c58fe8e01..baa067eb8cf4 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -1254,12 +1254,10 @@ static void ext4_group_desc_free(struct ext4_sb_info *sbi) struct buffer_head **group_desc; int i; - 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); - rcu_read_unlock(); } static void ext4_flex_groups_free(struct ext4_sb_info *sbi) @@ -1267,14 +1265,12 @@ static void ext4_flex_groups_free(struct ext4_sb_info *sbi) struct flex_groups **flex_groups; int i; - rcu_read_lock(); - 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(); } static void ext4_put_super(struct super_block *sb)