From: yangerkun yangerkun@huawei.com
mainline inclusion from mainline-5.5-rc3 commit a70fd5ac2ea787cafe07b69dadd16b3648ad64ac category: bugfix bugzilla: 25031 CVE: NA -----------------------------------
It's possible that __ext4_new_inode will release the xattr block, so it will trigger a warning since there is revoke credits will be 0 if the handle == NULL. The below scripts can reproduce it easily.
------------[ cut here ]------------ WARNING: CPU: 0 PID: 3861 at fs/jbd2/revoke.c:374 jbd2_journal_revoke+0x30e/0x540 fs/jbd2/revoke.c:374 ... __ext4_forget+0x1d7/0x800 fs/ext4/ext4_jbd2.c:248 ext4_free_blocks+0x213/0x1d60 fs/ext4/mballoc.c:4743 ext4_xattr_release_block+0x55b/0x780 fs/ext4/xattr.c:1254 ext4_xattr_block_set+0x1c2c/0x2c40 fs/ext4/xattr.c:2112 ext4_xattr_set_handle+0xa7e/0x1090 fs/ext4/xattr.c:2384 __ext4_set_acl+0x54d/0x6c0 fs/ext4/acl.c:214 ext4_init_acl+0x218/0x2e0 fs/ext4/acl.c:293 __ext4_new_inode+0x352a/0x42b0 fs/ext4/ialloc.c:1151 ext4_mkdir+0x2e9/0xbd0 fs/ext4/namei.c:2774 vfs_mkdir+0x386/0x5f0 fs/namei.c:3811 do_mkdirat+0x11c/0x210 fs/namei.c:3834 do_syscall_64+0xa1/0x530 arch/x86/entry/common.c:294 ... -------------------------------------
scripts: mkfs.ext4 /dev/vdb mount /dev/vdb /mnt cd /mnt && mkdir dir && for i in {1..8}; do setfacl -dm "u:user_"$i":rx" dir; done mkdir dir/dir1 && mv dir/dir1 ./ sh repro.sh && add some user
[root@localhost ~]# cat repro.sh while [ 1 -eq 1 ]; do rm -rf dir rm -rf dir1/dir1 mkdir dir for i in {1..8}; do setfacl -dm "u:test"$i":rx" dir; done setfacl -m "u:user_9:rx" dir & mkdir dir1/dir1 & done
Before exec repro.sh, dir1 has inherit the default acl from dir, and xattr block of dir1 dir is not the same, so the h_refcount of these two dir's xattr block will be 1. Then repro.sh can trigger the warning with the situation show as below. The last h_refcount can be clear with mkdir, and __ext4_new_inode has not reserved revoke credits, so the warning will happened, fix it by reserve revoke credits in __ext4_new_inode.
Thread 1 Thread 2 mkdir dir set default acl(will create a xattr block blk1 and the refcount of ext4_xattr_header will be 1) ... mkdir dir1/dir1 ->....->ext4_init_acl ->__ext4_set_acl(set default acl, will reuse blk1, and h_refcount will be 2)
setfacl->ext4_set_acl->... ->ext4_xattr_block_set(will create new block blk2 to store xattr)
->__ext4_set_acl(set access acl, since h_refcount of blk1 is 2, will create blk3 to store xattr)
->ext4_xattr_release_block(dec h_refcount of blk1 to 1) ->ext4_xattr_release_block(dec h_refcount and since it is 0, will release the block and trigger the warning)
Link: https://lore.kernel.org/r/20191213014900.47228-1-yangerkun@huawei.com Reported-by: Hulk Robot hulkci@huawei.com Reviewed-by: Jan Kara jack@suse.cz Signed-off-by: yangerkun yangerkun@huawei.com Signed-off-by: Theodore Ts'o tytso@mit.edu
Signed-off-by: zhangyi (F) yi.zhang@huawei.com Reviewed-by: Yang Erkun yangerkun@huawei.com Signed-off-by: Yang Yingliang yangyingliang@huawei.com --- fs/ext4/ialloc.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c index 0b5e65f..0abb72d 100644 --- a/fs/ext4/ialloc.c +++ b/fs/ext4/ialloc.c @@ -926,8 +926,8 @@ struct inode *__ext4_new_inode(handle_t *handle, struct inode *dir, if (!handle) { BUG_ON(nblocks <= 0); handle = __ext4_journal_start_sb(dir->i_sb, line_no, - handle_type, nblocks, - 0, 0); + handle_type, nblocks, 0, + ext4_trans_default_revoke_credits(sb)); if (IS_ERR(handle)) { err = PTR_ERR(handle); ext4_std_error(sb, err);