@@ -11,6 +11,7 @@
#include <linux/slab.h>
#include <linux/xattr.h>
#include <linux/posix_acl.h>
+#include <linux/mm.h>
#include <linux/module.h>
#include <linux/file.h>
#include <linux/hashtable.h>
@@ -392,6 +393,25 @@ static ssize_t ovl_read_iter(struct kiocb *iocb, struct iov_iter *to)
return ret;
}
+static int ovl_mmap(struct file *file, struct vm_area_struct *vma)
+{
+ if (likely(ovl_file_is_lower(file)))
+ return OVL_CALL_REAL_FOP(file, mmap(file, vma));
+
+ file = filp_clone_open(file);
+ if (IS_ERR(file))
+ return PTR_ERR(file);
+
+ fput(vma->vm_file);
+ /* transfer ref: */
+ vma->vm_file = file;
+
+ if (!file->f_op->mmap)
+ return -ENODEV;
+
+ return file->f_op->mmap(file, vma);
+}
+
static struct ovl_fops *ovl_fops_find(const struct file_operations *orig)
{
struct ovl_fops *ofop;
@@ -433,9 +453,10 @@ static struct ovl_fops *ovl_fops_get(struct file *file)
/* Intercept these: */
if (orig->read_iter)
ofop->fops.read_iter = ovl_read_iter;
+ if (orig->mmap)
+ ofop->fops.mmap = ovl_mmap;
/* These will need to be intercepted: */
- ofop->fops.mmap = orig->mmap;
ofop->fops.fsync = orig->fsync;
/*
... in order to handle the corner case when the file is copied up after being opened read-only and mapped shared. 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 cat << EOF > rorw-map.c #include <fcntl.h> #include <unistd.h> #include <string.h> #include <err.h> #include <sys/mman.h> int main(int argc, char *argv[]) { int rofd, rwfd; int ret; char buf[4]; char *addr; rofd = open(argv[1], O_RDONLY); if (rofd == -1) err(1, "ro open"); addr = mmap(NULL, 4, PROT_READ, MAP_SHARED, rofd, 0); if (addr == MAP_FAILED) err(1, "ro mmap"); if (memcmp(addr, "bubu", 4) == 0) errx(1, "identical startup data"); rwfd = open(argv[1], O_WRONLY); if (rwfd == -1) err(1, "rw open"); ret = write(rwfd, "bubu", 4); if (ret == -1) err(1, "write"); if (ret < 4) errx(1, "short write"); if (memcmp(addr, "bubu", 4) != 0) errx(1, "bad mmap data"); ret = read(rofd, buf, 4); if (ret == -1) err(1, "read"); if (ret < 4) errx(1, "short read"); if (memcmp(buf, "bubu", 4) != 0) errx(1, "bad read data"); return 0; } EOF gcc -o rorw-map rorw-map.c mkdir -p mnt lower upper work echo baba > lower/foo mount -t overlay overlay -olowerdir=lower,upperdir=upper,workdir=work mnt ./rorw-map mnt/foo umount mnt - 8< - - - - - 8< - - - - - 8< - - - - - 8< - - - - No output means success, "rorw-map: bad mmap data" means failure. Signed-off-by: Miklos Szeredi <mszeredi@redhat.com> --- fs/overlayfs/inode.c | 23 ++++++++++++++++++++++- 1 file changed, 22 insertions(+), 1 deletion(-)