@@ -12,6 +12,7 @@
#include <linux/xattr.h>
#include <linux/posix_acl.h>
#include <linux/module.h>
+#include <linux/file.h>
#include <linux/hashtable.h>
#include "overlayfs.h"
@@ -368,6 +369,29 @@ void ovl_cleanup_fops_htable(void)
__ofop->orig_fops->call; \
})
+static bool ovl_file_is_lower(struct file *file)
+{
+ return !OVL_TYPE_UPPER(ovl_path_type(file->f_path.dentry));
+}
+
+static ssize_t ovl_read_iter(struct kiocb *iocb, struct iov_iter *to)
+{
+ struct file *file = iocb->ki_filp;
+ ssize_t ret;
+
+ if (likely(ovl_file_is_lower(file)))
+ return OVL_CALL_REAL_FOP(file, read_iter(iocb, to));
+
+ file = filp_clone_open(file);
+ if (IS_ERR(file))
+ return PTR_ERR(file);
+
+ ret = vfs_iter_read(file, to, &iocb->ki_pos);
+ fput(file);
+
+ return ret;
+}
+
static struct ovl_fops *ovl_fops_find(const struct file_operations *orig)
{
struct ovl_fops *ofop;
@@ -406,8 +430,11 @@ static struct ovl_fops *ovl_fops_get(struct file *file)
ofop->magic = OVL_FOPS_MAGIC;
ofop->orig_fops = fops_get(orig);
+ /* Intercept these: */
+ if (orig->read_iter)
+ ofop->fops.read_iter = ovl_read_iter;
+
/* These will need to be intercepted: */
- ofop->fops.read_iter = orig->read_iter;
ofop->fops.mmap = orig->mmap;
ofop->fops.fsync = orig->fsync;
...in order to handle the corner case when the file is copyied up after being opened read-only. Can be verified with the following script: - 8< - - - - - 8< - - - - - 8< - - - - - 8< - - - - cd / rm -rf /tmp/ovl-rorw-test mkdir /tmp/ovl-rorw-test cd /tmp/ovl-rorw-test mkdir -p mnt lower upper work echo baba > lower/foo mount -t overlay overlay -olowerdir=lower,upperdir=upper,workdir=work mnt exec 3< mnt/foo echo bubu > mnt/foo cat <&3 exec 3>&- umount mnt - 8< - - - - - 8< - - - - - 8< - - - - - 8< - - - - Correct output is "bubu", incorrect output is "baba". Signed-off-by: Miklos Szeredi <mszeredi@redhat.com> --- fs/overlayfs/inode.c | 29 ++++++++++++++++++++++++++++- 1 file changed, 28 insertions(+), 1 deletion(-)