4.8-stable review patch. If anyone has any objections, please let me know.
------------------
From: Miklos Szeredi <mszeredi@xxxxxxxxxx>
commit f2b20f6ee842313a0d681dbbf7f87b70291a6a3b upstream.
This fixes a bug where the permission was not properly checked in
overlayfs. The testcase is ltp/utimensat01.
It is also cleaner and safer to do the permission checking in the vfs
helper instead of the caller.
This patch introduces an additional ia_valid flag ATTR_TOUCH (since
touch(1) is the most obvious user of utimes(NULL)) that is passed into
notify_change whenever the conditions for this special permission checking
mode are met.
Reported-by: Aihua Zhang <zhangaihua1@xxxxxxxxxx>
Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxxxxx>
Tested-by: Aihua Zhang <zhangaihua1@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/attr.c | 15 +++++++++++++++
fs/utimes.c | 17 +----------------
include/linux/fs.h | 1 +
3 files changed, 17 insertions(+), 16 deletions(-)
--- a/fs/attr.c
+++ b/fs/attr.c
@@ -202,6 +202,21 @@ int notify_change(struct dentry * dentry
return -EPERM;
}
+ /*
+ * If utimes(2) and friends are called with times == NULL (or both
+ * times are UTIME_NOW), then we need to check for write permission
+ */
+ if (ia_valid & ATTR_TOUCH) {
+ if (IS_IMMUTABLE(inode))
+ return -EPERM;
+
+ if (!inode_owner_or_capable(inode)) {
+ error = inode_permission(inode, MAY_WRITE);
+ if (error)
+ return error;
+ }
+ }
+
if ((ia_valid & ATTR_MODE)) {
umode_t amode = attr->ia_mode;
/* Flag setting protected by i_mutex */
--- a/fs/utimes.c
+++ b/fs/utimes.c
@@ -87,21 +87,7 @@ static int utimes_common(struct path *pa
*/
newattrs.ia_valid |= ATTR_TIMES_SET;
} else {
- /*
- * If times is NULL (or both times are UTIME_NOW),
- * then we need to check permissions, because
- * inode_change_ok() won't do it.
- */
- error = -EPERM;
- if (IS_IMMUTABLE(inode))
- goto mnt_drop_write_and_out;
-
- error = -EACCES;
- if (!inode_owner_or_capable(inode)) {
- error = inode_permission(inode, MAY_WRITE);
- if (error)
- goto mnt_drop_write_and_out;
- }
+ newattrs.ia_valid |= ATTR_TOUCH;
}
retry_deleg:
inode_lock(inode);
@@ -113,7 +99,6 @@ retry_deleg:
goto retry_deleg;
}
-mnt_drop_write_and_out:
mnt_drop_write(path->mnt);
out:
return error;
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -224,6 +224,7 @@ typedef int (dio_iodone_t)(struct kiocb
#define ATTR_KILL_PRIV (1 << 14)
#define ATTR_OPEN (1 << 15) /* Truncating from open(O_TRUNC) */
#define ATTR_TIMES_SET (1 << 16)
+#define ATTR_TOUCH (1 << 17)
/*
* Whiteout is represented by a char device. The following constants define the
--
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