ext4: fix superblock checksum failure when setting password salt

stable inclusion
from stable-5.10.9
commit cd223237e792e86ae8b1c37df6e262a870ae11bc
bugzilla: 47457

--------------------------------

commit dfd56c2c upstream.

When setting password salt in the superblock, we forget to recompute the
superblock checksum so it will not match until the next superblock
modification which recomputes the checksum. Fix it.

CC: Michael Halcrow <mhalcrow@google.com>
Reported-by: NAndreas Dilger <adilger@dilger.ca>
Fixes: 9bd8212f ("ext4 crypto: add encryption policy and password salt support")
Signed-off-by: NJan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20201216101844.22917-8-jack@suse.czSigned-off-by: NTheodore Ts'o <tytso@mit.edu>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Acked-by: NXie XiuQi <xiexiuqi@huawei.com>

fs/ext4/ioctl.c

@@ -1157,7 +1157,10 @@ static long __ext4_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 			err = ext4_journal_get_write_access(handle, sbi->s_sbh);
 			if (err)
 				goto pwsalt_err_journal;
+			lock_buffer(sbi->s_sbh);
 			generate_random_uuid(sbi->s_es->s_encrypt_pw_salt);
+			ext4_superblock_csum_set(sb);
+			unlock_buffer(sbi->s_sbh);
 			err = ext4_handle_dirty_metadata(handle, NULL,
 							 sbi->s_sbh);
 		pwsalt_err_journal: