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Commit 03bea604 authored by Miklos Szeredi's avatar Miklos Szeredi
Browse files

ovl: get_write_access() in truncate 



When truncating a file we should check write access on the underlying
inode.  And we should do so on the lower file as well (before copy-up) for
consistency.

Original patch and test case by Aihua Zhang.

 - - >o >o - - test.c - - >o >o - -
#include <stdio.h>
#include <errno.h>
#include <unistd.h>

int main(int argc, char *argv[])
{
	int ret;

	ret = truncate(argv[0], 4096);
	if (ret != -1) {
		fprintf(stderr, "truncate(argv[0]) should have failed\n");
		return 1;
	}
	if (errno != ETXTBSY) {
		perror("truncate(argv[0])");
		return 1;
	}

	return 0;
}
 - - >o >o - - >o >o - - >o >o - -

Reported-by: default avatarAihua Zhang <zhangaihua1@huawei.com>
Signed-off-by: default avatarMiklos Szeredi <mszeredi@redhat.com>
Cc: <stable@vger.kernel.org>
parent a4859d75

fs/overlayfs/inode.c

+21 −0
Original line number Diff line number Diff line
@@ -59,16 +59,37 @@ int ovl_setattr(struct dentry *dentry, struct iattr *attr) 
	if (err)

		goto out;



	if (attr->ia_valid & ATTR_SIZE) {

		struct inode *realinode = d_inode(ovl_dentry_real(dentry));



		err = -ETXTBSY;

		if (atomic_read(&realinode->i_writecount) < 0)

			goto out_drop_write;

	}



	err = ovl_copy_up(dentry);

	if (!err) {

		struct inode *winode = NULL;



		upperdentry = ovl_dentry_upper(dentry);



		if (attr->ia_valid & ATTR_SIZE) {

			winode = d_inode(upperdentry);

			err = get_write_access(winode);

			if (err)

				goto out_drop_write;

		}



		inode_lock(upperdentry->d_inode);

		err = notify_change(upperdentry, attr, NULL);

		if (!err)

			ovl_copyattr(upperdentry->d_inode, dentry->d_inode);

		inode_unlock(upperdentry->d_inode);



		if (winode)

			put_write_access(winode);

	}

out_drop_write:

	ovl_drop_write(dentry);

out:

	return err;