[PATCH 4.9.y] ubifs: Massage assert in ubifs_xattr_set() wrt. init_xattrs

[Julia Cartwright <julia@ni.com>]

From: Xiaolei Li <xiaolei.li@mediatek.com>

This is a conceptual cherry-pick of commit
d8db5b1ca9d4c57e49893d0f78e6d5ce81450cc8 upstream.

The inode is not locked in init_xattrs when creating a new inode.

Without this patch, there will occurs assert when booting or creating
a new file, if the kernel config CONFIG_SECURITY_SMACK is enabled.

Log likes:

UBIFS assert failed in ubifs_xattr_set at 298 (pid 1156)
CPU: 1 PID: 1156 Comm: ldconfig Tainted: G S 4.12.0-rc1-207440-g1e70b02 #2
Hardware name: MediaTek MT2712 evaluation board (DT)
Call trace:
[<ffff000008088538>] dump_backtrace+0x0/0x238
[<ffff000008088834>] show_stack+0x14/0x20
[<ffff0000083d98d4>] dump_stack+0x9c/0xc0
[<ffff00000835d524>] ubifs_xattr_set+0x374/0x5e0
[<ffff00000835d7ec>] init_xattrs+0x5c/0xb8
[<ffff000008385788>] security_inode_init_security+0x110/0x190
[<ffff00000835e058>] ubifs_init_security+0x30/0x68
[<ffff00000833ada0>] ubifs_mkdir+0x100/0x200
[<ffff00000820669c>] vfs_mkdir+0x11c/0x1b8
[<ffff00000820b73c>] SyS_mkdirat+0x74/0xd0
[<ffff000008082f8c>] __sys_trace_return+0x0/0x4

Signed-off-by: Xiaolei Li <xiaolei.li@mediatek.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
Cc: stable@vger.kernel.org
(julia: massaged to apply to 4.9.y, which doesn't contain fscrypto support)
Signed-off-by: Julia Cartwright <julia@ni.com>
---
Hey all-

We reproduced the issue fixed upstream by Xiaolei Li's commit in 4.9.y,
with the very similar backtrace:

   UBIFS assert failed in __ubifs_setxattr at 282 (pid 1362)
   CPU: 1 PID: 1362 Comm: sed Not tainted 4.9.47-rt37 #1
   Backtrace:
      (dump_backtrace) from (show_stack+0x20/0x24)
      (show_stack) from (dump_stack+0x80/0xa0)
      (dump_stack) from (__ubifs_setxattr+0x84/0x634)
      (__ubifs_setxattr) from (init_xattrs+0x70/0xac)
      (init_xattrs) from (security_inode_init_security+0x100/0x144)
      (security_inode_init_security) from (ubifs_init_security+0x38/0x6c)
      (ubifs_init_security) from (ubifs_create+0xe8/0x1fc)
      (ubifs_create) from (path_openat+0x97c/0x1090)
      (path_openat) from (do_filp_open+0x48/0x94)
      (do_filp_open) from (do_sys_open+0x134/0x1d8)
      (do_sys_open) from (SyS_open+0x30/0x34)
      (SyS_open) from (ret_fast_syscall+0x0/0x3c)

Please consider applying this to 4.9.y at the very least, it may apply
further back as well.

Thanks!
   Julia

 fs/ubifs/xattr.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/fs/ubifs/xattr.c b/fs/ubifs/xattr.c
index d9f9615bfd71..3979d767a0cb 100644
--- a/fs/ubifs/xattr.c
+++ b/fs/ubifs/xattr.c
@@ -270,7 +270,8 @@ static struct inode *iget_xattr(struct ubifs_info *c, ino_t inum)
 }
 
 static int __ubifs_setxattr(struct inode *host, const char *name,
-			    const void *value, size_t size, int flags)
+			    const void *value, size_t size, int flags,
+			    bool check_lock)
 {
 	struct inode *inode;
 	struct ubifs_info *c = host->i_sb->s_fs_info;
@@ -279,7 +280,8 @@ static int __ubifs_setxattr(struct inode *host, const char *name,
 	union ubifs_key key;
 	int err;
 
-	ubifs_assert(inode_is_locked(host));
+	if (check_lock)
+		ubifs_assert(inode_is_locked(host));
 
 	if (size > UBIFS_MAX_INO_DATA)
 		return -ERANGE;
@@ -548,7 +550,8 @@ static int init_xattrs(struct inode *inode, const struct xattr *xattr_array,
 		}
 		strcpy(name, XATTR_SECURITY_PREFIX);
 		strcpy(name + XATTR_SECURITY_PREFIX_LEN, xattr->name);
-		err = __ubifs_setxattr(inode, name, xattr->value, xattr->value_len, 0);
+		err = __ubifs_setxattr(inode, name, xattr->value,
+				       xattr->value_len, 0, false);
 		kfree(name);
 		if (err < 0)
 			break;
@@ -594,7 +597,8 @@ static int ubifs_xattr_set(const struct xattr_handler *handler,
 	name = xattr_full_name(handler, name);
 
 	if (value)
-		return __ubifs_setxattr(inode, name, value, size, flags);
+		return __ubifs_setxattr(inode, name, value, size, flags,
+					true);
 	else
 		return __ubifs_removexattr(inode, name);
 }
-- 
2.16.1