linux-kernel - Re: [syzbot] [btrfs?] KASAN: slab-out-of-bounds Read in getname

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Date: Tue, 19 Dec 2023 12:59:22 +0800
From: Edward Adam Davis <eadavis@...com>
To: syzbot+33f23b49ac24f986c9e8@...kaller.appspotmail.com
Cc: linux-kernel@...r.kernel.org,
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [btrfs?] KASAN: slab-out-of-bounds Read in getname_kernel (2)

please test slab-out-of-bounds Read in getname_kernel

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 3bd7d7488169

diff --git a/fs/btrfs/dev-replace.c b/fs/btrfs/dev-replace.c
index f9544fda38e9..b7e8392d34dc 100644
--- a/fs/btrfs/dev-replace.c
+++ b/fs/btrfs/dev-replace.c
@@ -741,7 +741,8 @@ int btrfs_dev_replace_by_ioctl(struct btrfs_fs_info *fs_info,
 	}
 
 	if ((args->start.srcdevid == 0 && args->start.srcdev_name[0] == '\0') ||
-	    args->start.tgtdev_name[0] == '\0')
+	    args->start.tgtdev_name[0] == '\0' ||
+	    !args->start.tgtdev_name[0])
 		return -EINVAL;
 
 	ret = btrfs_dev_replace_start(fs_info, args->start.tgtdev_name,
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 4e50b62db2a8..43a508cea759 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -3272,7 +3272,7 @@ static long btrfs_ioctl_get_dev_stats(struct btrfs_fs_info *fs_info,
 static long btrfs_ioctl_dev_replace(struct btrfs_fs_info *fs_info,
 				    void __user *arg)
 {
-	struct btrfs_ioctl_dev_replace_args *p;
+	struct btrfs_ioctl_dev_replace_args p = {};
 	int ret;
 
 	if (!capable(CAP_SYS_ADMIN))
@@ -3283,11 +3283,10 @@ static long btrfs_ioctl_dev_replace(struct btrfs_fs_info *fs_info,
 		return -EINVAL;
 	}
 
-	p = memdup_user(arg, sizeof(*p));
-	if (IS_ERR(p))
-		return PTR_ERR(p);
+	if (copy_from_user(&p, arg, sizeof(p)))
+		return -EINVAL;
 
-	switch (p->cmd) {
+	switch (p.cmd) {
 	case BTRFS_IOCTL_DEV_REPLACE_CMD_START:
 		if (sb_rdonly(fs_info->sb)) {
 			ret = -EROFS;
@@ -3296,16 +3295,16 @@ static long btrfs_ioctl_dev_replace(struct btrfs_fs_info *fs_info,
 		if (!btrfs_exclop_start(fs_info, BTRFS_EXCLOP_DEV_REPLACE)) {
 			ret = BTRFS_ERROR_DEV_EXCL_RUN_IN_PROGRESS;
 		} else {
-			ret = btrfs_dev_replace_by_ioctl(fs_info, p);
+			ret = btrfs_dev_replace_by_ioctl(fs_info, &p);
 			btrfs_exclop_finish(fs_info);
 		}
 		break;
 	case BTRFS_IOCTL_DEV_REPLACE_CMD_STATUS:
-		btrfs_dev_replace_status(fs_info, p);
+		btrfs_dev_replace_status(fs_info, &p);
 		ret = 0;
 		break;
 	case BTRFS_IOCTL_DEV_REPLACE_CMD_CANCEL:
-		p->result = btrfs_dev_replace_cancel(fs_info);
+		p.result = btrfs_dev_replace_cancel(fs_info);
 		ret = 0;
 		break;
 	default:
@@ -3313,10 +3312,9 @@ static long btrfs_ioctl_dev_replace(struct btrfs_fs_info *fs_info,
 		break;
 	}
 
-	if ((ret == 0 || ret == -ECANCELED) && copy_to_user(arg, p, sizeof(*p)))
+	if ((ret == 0 || ret == -ECANCELED) && copy_to_user(arg, &p, sizeof(p)))
 		ret = -EFAULT;
 out:
-	kfree(p);
 	return ret;
 }