summaryrefslogtreecommitdiff
diff options
context:
space:
mode:
authorLinus Torvalds <torvalds@linux-foundation.org>2020-01-26 10:33:48 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2020-01-26 10:33:48 -0800
commitb1b298914f3ae226e99c98042c1648f740015724 (patch)
treea612078abd42ff5d826beffd693ab7d4c90d6d5d
parenta45ea48e2bcd92c1f678b794f488ca0bda9835b8 (diff)
parentd0cb50185ae942b03c4327be322055d622dc79f6 (diff)
Merge branch 'fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
Pull vfs fix from Al Viro: "Fix a use-after-free in do_last() handling of sysctl_protected_... checks. The use-after-free normally doesn't happen there, but race with rename() and it becomes possible" * 'fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: do_last(): fetch directory ->i_mode and ->i_uid before it's too late
-rw-r--r--fs/namei.c17
1 files changed, 10 insertions, 7 deletions
diff --git a/fs/namei.c b/fs/namei.c
index d2720dc71d0e..4fb61e0754ed 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1001,7 +1001,8 @@ 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:
@@ -1017,18 +1018,18 @@ 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))))) {
const char *operation = S_ISFIFO(inode->i_mode) ?
@@ -3201,6 +3202,8 @@ static int do_last(struct nameidata *nd,
struct file *file, const struct open_flags *op)
{
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;
@@ -3331,7 +3334,7 @@ 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;