Re: [syzbot] Re: general protection fault in jfs_error()

[syzbot <syzbot+5f0d7af0e45fae10edd1@syzkaller.appspotmail.com>]

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Subject: Re: general protection fault in jfs_error()
Author: dmantipov@yandex.ru

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git adc218676eef25575469234709c2d87185ca223a

diff --git a/fs/jfs/namei.c b/fs/jfs/namei.c
index d68a4e6ac345..d2eff3375aad 100644
--- a/fs/jfs/namei.c
+++ b/fs/jfs/namei.c
@@ -96,24 +96,29 @@ static int jfs_create(struct mnt_idmap *idmap, struct inode *dip,
 	}
 
 	tid = txBegin(dip->i_sb, 0);
+	/* Do not go further if jfs_handle_error() marks us read-only. */
+	if (unlikely(dip->i_sb->s_flags & SB_RDONLY)) {
+		rc = -EROFS;
+		goto out3;
+	}
 
 	mutex_lock_nested(&JFS_IP(dip)->commit_mutex, COMMIT_MUTEX_PARENT);
 	mutex_lock_nested(&JFS_IP(ip)->commit_mutex, COMMIT_MUTEX_CHILD);
 
 	rc = jfs_init_acl(tid, ip, dip);
 	if (rc)
-		goto out3;
+		goto out4;
 
 	rc = jfs_init_security(tid, ip, dip, &dentry->d_name);
 	if (rc) {
 		txAbort(tid, 0);
-		goto out3;
+		goto out4;
 	}
 
 	if ((rc = dtSearch(dip, &dname, &ino, &btstack, JFS_CREATE))) {
 		jfs_err("jfs_create: dtSearch returned %d", rc);
 		txAbort(tid, 0);
-		goto out3;
+		goto out4;
 	}
 
 	tblk = tid_to_tblock(tid);
@@ -140,7 +145,7 @@ static int jfs_create(struct mnt_idmap *idmap, struct inode *dip,
 			txAbort(tid, 1);	/* Marks Filesystem dirty */
 		} else
 			txAbort(tid, 0);	/* Filesystem full */
-		goto out3;
+		goto out4;
 	}
 
 	ip->i_op = &jfs_file_inode_operations;
@@ -155,10 +160,12 @@ static int jfs_create(struct mnt_idmap *idmap, struct inode *dip,
 
 	rc = txCommit(tid, 2, &iplist[0], 0);
 
-      out3:
+      out4:
 	txEnd(tid);
 	mutex_unlock(&JFS_IP(ip)->commit_mutex);
 	mutex_unlock(&JFS_IP(dip)->commit_mutex);
+
+      out3:
 	if (rc) {
 		free_ea_wmap(ip);
 		clear_nlink(ip);