[PATCH V6 01/10] null_blk: use DEFINE_MUTEX for the file-scope mutex
Zizhi Wo <[email protected]>
| Newsgroups | org.kernel.vger.linux-block |
|---|---|
| Message-ID | <[email protected]> |
From: Zizhi Wo <[email protected]> In null_init(), mutex_init(&lock) currently happens after configfs_register_subsystem(), which exposes the nullb subsystem to userspace. A racing mkdir() into /sys/kernel/config/nullb/ can reach null_find_dev_by_name() -> mutex_lock(&lock) before the mutex is initialized, trigger warning: [ 123.137788] DEBUG_LOCKS_WARN_ON(lock->magic != lock) [ 123.137796] WARNING: kernel/locking/mutex.c:159 at mutex_lock+0x171/0x1c0, CPU#13: mkdir/1301 [ 123.140090] Modules linked in: null_blk(+) nft_fib_inet nft_fib_ipv4 ...... [ 123.154926] Call Trace: [ 123.155172] <TASK> [ 123.155419] ? __pfx_mutex_lock+0x10/0x10 [ 123.156181] ? __pfx__raw_spin_lock+0x10/0x10 [ 123.156571] nullb_group_make_group+0x20/0x100 [null_blk] [ 123.157011] configfs_mkdir+0x47b/0xc70 [ 123.157337] ? __pfx_configfs_mkdir+0x10/0x10 [ 123.157719] ? may_create_dentry+0x242/0x2e0 [ 123.158061] vfs_mkdir+0x2a9/0x6c0 [ 123.158352] filename_mkdirat+0x3dc/0x500 [ 123.158710] ? __pfx_filename_mkdirat+0x10/0x10 [ 123.159070] ? strncpy_from_user+0x3a/0x1d0 [ 123.159413] __x64_sys_mkdir+0x6b/0x90 [ 123.159760] do_syscall_64+0xea/0x600 Replace the runtime mutex_init(&lock) with a static DEFINE_MUTEX(lock) declaration to fix this issue. Fixes: 49c3b9266a71 ("block: null_blk: Improve device creation with configfs") Suggested-by: Bart Van Assche <[email protected]> Signed-off-by: Zizhi Wo <[email protected]> Reviewed-by: Bart Van Assche <[email protected]> Reviewed-by: Damien Le Moal <[email protected]> Reviewed-by: Nilay Shroff <[email protected]> --- drivers/block/null_blk/main.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) diff --git a/drivers/block/null_blk/main.c b/drivers/block/null_blk/main.c index f8c0fd57e041..eba204b27785 100644 --- a/drivers/block/null_blk/main.c +++ b/drivers/block/null_blk/main.c @@ -66,7 +66,7 @@ struct nullb_page { #define NULLB_PAGE_FREE (MAP_SZ - 2) static LIST_HEAD(nullb_list); -static struct mutex lock; +static DEFINE_MUTEX(lock); static int null_major; static DEFINE_IDA(nullb_indexes); static struct blk_mq_tag_set tag_set; @@ -2166,8 +2166,6 @@ static int __init null_init(void) if (ret) return ret; - mutex_init(&lock); - null_major = register_blkdev(0, "nullb"); if (null_major < 0) { ret = null_major; -- 2.52.0