...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@xxxxxxxxxx>
---
fs/overlayfs/inode.c | 29 ++++++++++++++++++++++++++++-
1 file changed, 28 insertions(+), 1 deletion(-)
diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index 3e26615c4697..09c6f99bd5db 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -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;
@@ -404,8 +428,11 @@ 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;
--
2.5.5
--
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