From: Al Viro <viro@zeniv.linux.org.uk>
Date: Sun, 26 Jan 2020 14:29:34 +0000 (-0500)
Subject: [RAMEN9610-21564]do_last(): fetch directory ->i_mode and ->i_uid before it's too... 
X-Git-Tag: MMI-QSAS30.62-33-3~4
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=3b938c79c2852401c3f8453e25a302adc547a3f5;p=GitHub%2FMotorolaMobilityLLC%2Fkernel-slsi.git

[RAMEN9610-21564]do_last(): fetch directory ->i_mode and ->i_uid before it's too late

commit d0cb50185ae942b03c4327be322055d622dc79f6 upstream.

may_create_in_sticky() call is done when we already have dropped the
reference to dir.

Change-Id: Ied338ffbf1c0ab7a9ed65dfb25fc44bde879d64b
Fixes: 30aba6656f61e (namei: allow restricted O_CREAT of FIFOs and regular files)
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit e6bdd445f7b580a8e28e33ef16f9c86ccf8730d4)
---

diff --git a/fs/namei.c b/fs/namei.c
index d33064a40420..0c57b3cae0fe 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1038,7 +1038,8 @@ static int may_linkat(struct path *link)
  * may_create_in_sticky - Check whether an O_CREAT open in a sticky directory
  *			  should be allowed, or not, on files that already
  *			  exist.
- * @dir: the sticky parent directory
+ * @dir_mode: mode bits of directory
+ * @dir_uid: owner of directory
  * @inode: the inode of the file to open
  *
  * Block an O_CREAT open of a FIFO (or a regular file) when:
@@ -1054,18 +1055,18 @@ static int may_linkat(struct path *link)
  *
  * Returns 0 if the open is allowed, -ve on error.
  */
-static int may_create_in_sticky(struct dentry * const dir,
+static int may_create_in_sticky(umode_t dir_mode, kuid_t dir_uid,
 				struct inode * const inode)
 {
 	if ((!sysctl_protected_fifos && S_ISFIFO(inode->i_mode)) ||
 	    (!sysctl_protected_regular && S_ISREG(inode->i_mode)) ||
-	    likely(!(dir->d_inode->i_mode & S_ISVTX)) ||
-	    uid_eq(inode->i_uid, dir->d_inode->i_uid) ||
+	    likely(!(dir_mode & S_ISVTX)) ||
+	    uid_eq(inode->i_uid, dir_uid) ||
 	    uid_eq(current_fsuid(), inode->i_uid))
 		return 0;
 
-	if (likely(dir->d_inode->i_mode & 0002) ||
-	    (dir->d_inode->i_mode & 0020 &&
+	if (likely(dir_mode & 0002) ||
+	    (dir_mode & 0020 &&
 	     ((sysctl_protected_fifos >= 2 && S_ISFIFO(inode->i_mode)) ||
 	      (sysctl_protected_regular >= 2 && S_ISREG(inode->i_mode))))) {
 		return -EACCES;
@@ -3295,6 +3296,8 @@ static int do_last(struct nameidata *nd,
 		   int *opened)
 {
 	struct dentry *dir = nd->path.dentry;
+	kuid_t dir_uid = dir->d_inode->i_uid;
+	umode_t dir_mode = dir->d_inode->i_mode;
 	int open_flag = op->open_flag;
 	bool will_truncate = (open_flag & O_TRUNC) != 0;
 	bool got_write = false;
@@ -3430,7 +3433,7 @@ finish_open:
 		error = -EISDIR;
 		if (d_is_dir(nd->path.dentry))
 			goto out;
-		error = may_create_in_sticky(dir,
+		error = may_create_in_sticky(dir_mode, dir_uid,
 					     d_backing_inode(nd->path.dentry));
 		if (unlikely(error))
 			goto out;