Newly created file on ext2 inherits inode flags from parent directory,
so new inode created in append-only directory has S_APPEND flag set,
may_open() called by do_last() checks that flag then returns -EPERM,
but at that time the new inode is already created.
This can be reproduced by:
# mkdir -p /mnt/ext2/append-only
# chattr +a /mnt/ext2/append-only
# ./opentest /mnt/ext2/append-only/newtestfile
# ls -l /mnt/ext2/append-only/newtestfile
opentest will return 'Operation not permitted', but the ls shows that
newtestfile is already created.
# cat opentest.c
#include <stdio.h>
#include <sys/types.h>
#include <fcntl.h>
#include <sys/stat.h>
int main(int argc, char *argv[])
{
int fd;
fd = open(argv[1], O_RDWR|O_CREAT, 0666);
if (fd == -1)
perror("open failed");
return 0;
}
To avoid this, check EXT2_APPEND_FL flag first in ext2_create before
really allocating new inode.
Cc: Jan Kara <[email protected]>
Signed-off-by: Eryu Guan <[email protected]>
---
fs/ext2/namei.c | 11 +++++++++++
1 files changed, 11 insertions(+), 0 deletions(-)
diff --git a/fs/ext2/namei.c b/fs/ext2/namei.c
index 761fde8..b9f8998 100644
--- a/fs/ext2/namei.c
+++ b/fs/ext2/namei.c
@@ -32,6 +32,7 @@
#include <linux/pagemap.h>
#include <linux/quotaops.h>
+#include <linux/namei.h>
#include "ext2.h"
#include "xattr.h"
#include "acl.h"
@@ -97,6 +98,16 @@ struct dentry *ext2_get_parent(struct dentry *child)
static int ext2_create (struct inode * dir, struct dentry * dentry, int mode, struct nameidata *nd)
{
struct inode *inode;
+ int open_flag = nd->intent.open.file->f_flags;
+
+ if ((EXT2_I(dir)->i_flags & EXT2_FL_INHERITED) & EXT2_APPEND_FL) {
+ if ((open_flag & O_ACCMODE) != O_RDONLY &&
+ !(open_flag & O_APPEND))
+ return -EPERM;
+ if (open_flag & O_TRUNC)
+ return -EPERM;
+ }
+
dquot_initialize(dir);
--
1.7.7.1