[PATCH v3] btrfs: Replace strncpy() with strscpy()

[Artem Chernyshev]

Using strncpy() on NUL-terminated strings are deprecated.
To avoid possible forming of non-terminated string
strscpy() could be used.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: 475f63874d73 ("btrfs: new ioctls for scrub")
Fixes: 606686eeac45 ("Btrfs: use rcu to protect device->name")
Signed-off-by: Artem Chernyshev <artem.chernyshev@xxxxxxxxxxx>
---
V1->V2 Fixed typo in subject
V2->V3 Added fix for ioctl.c

 fs/btrfs/ioctl.c      | 5 ++---
 fs/btrfs/rcu-string.h | 5 ++++-
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index d5dd8bed1488..fdf62d514662 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -3748,9 +3748,8 @@ static long btrfs_ioctl_dev_info(struct btrfs_fs_info *fs_info,
 	di_args->total_bytes = btrfs_device_get_total_bytes(dev);
 	memcpy(di_args->uuid, dev->uuid, sizeof(di_args->uuid));
 	if (dev->name) {
-		strncpy(di_args->path, rcu_str_deref(dev->name),
-				sizeof(di_args->path) - 1);
-		di_args->path[sizeof(di_args->path) - 1] = 0;
+		strscpy(di_args->path, rcu_str_deref(dev->name),
+				sizeof(di_args->path));
 	} else {
 		di_args->path[0] = '\0';
 	}
diff --git a/fs/btrfs/rcu-string.h b/fs/btrfs/rcu-string.h
index 5c1a617eb25d..d9894da7a05a 100644
--- a/fs/btrfs/rcu-string.h
+++ b/fs/btrfs/rcu-string.h
@@ -18,7 +18,10 @@ static inline struct rcu_string *rcu_string_strdup(const char *src, gfp_t mask)
 					 (len * sizeof(char)), mask);
 	if (!ret)
 		return ret;
-	strncpy(ret->str, src, len);
+	if (WARN_ON(strscpy(ret->str, src, len) < 0)) {
+		kfree(ret);
+		return NULL;
+	}
 	return ret;
 }
 
-- 
2.30.3